diff options
48 files changed, 707 insertions, 425 deletions
diff --git a/arch/alpha/include/asm/processor.h b/arch/alpha/include/asm/processor.h index 6cb7fe8..b4cf036 100644 --- a/arch/alpha/include/asm/processor.h +++ b/arch/alpha/include/asm/processor.h @@ -57,6 +57,7 @@ unsigned long get_wchan(struct task_struct *p); ((tsk) == current ? rdusp() : task_thread_info(tsk)->pcb.usp) #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() #define ARCH_HAS_PREFETCH #define ARCH_HAS_PREFETCHW diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h index d99f9b3..82588f3 100644 --- a/arch/arc/include/asm/processor.h +++ b/arch/arc/include/asm/processor.h @@ -62,6 +62,8 @@ unsigned long thread_saved_pc(struct task_struct *t); #define cpu_relax() do { } while (0) #endif +#define cpu_relax_lowlatency() cpu_relax() + #define copy_segments(tsk, mm) do { } while (0) #define release_segments(mm) do { } while (0) diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h index c3d5fc1..8a1e8e9 100644 --- a/arch/arm/include/asm/processor.h +++ b/arch/arm/include/asm/processor.h @@ -82,6 +82,8 @@ unsigned long get_wchan(struct task_struct *p); #define cpu_relax() barrier() #endif +#define cpu_relax_lowlatency() cpu_relax() + #define task_pt_regs(p) \ ((struct pt_regs *)(THREAD_START_SP + task_stack_page(p)) - 1) diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 7771245..3df21fe 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -129,6 +129,7 @@ extern void release_thread(struct task_struct *); unsigned long get_wchan(struct task_struct *p); #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() /* Thread switching */ extern struct task_struct *cpu_switch_to(struct task_struct *prev, diff --git a/arch/avr32/include/asm/processor.h b/arch/avr32/include/asm/processor.h index 972adcc..941593c 100644 --- a/arch/avr32/include/asm/processor.h +++ b/arch/avr32/include/asm/processor.h @@ -92,6 +92,7 @@ extern struct avr32_cpuinfo boot_cpu_data; #define TASK_UNMAPPED_BASE (PAGE_ALIGN(TASK_SIZE / 3)) #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() #define cpu_sync_pipeline() asm volatile("sub pc, -2" : : : "memory") struct cpu_context { diff --git a/arch/blackfin/include/asm/processor.h b/arch/blackfin/include/asm/processor.h index d0e72e9..7acd466 100644 --- a/arch/blackfin/include/asm/processor.h +++ b/arch/blackfin/include/asm/processor.h @@ -99,7 +99,7 @@ unsigned long get_wchan(struct task_struct *p); #define KSTK_ESP(tsk) ((tsk) == current ? rdusp() : (tsk)->thread.usp) #define cpu_relax() smp_mb() - +#define cpu_relax_lowlatency() cpu_relax() /* Get the Silicon Revision of the chip */ static inline uint32_t __pure bfin_revid(void) diff --git a/arch/c6x/include/asm/processor.h b/arch/c6x/include/asm/processor.h index b9eb3da..f2ef31b 100644 --- a/arch/c6x/include/asm/processor.h +++ b/arch/c6x/include/asm/processor.h @@ -121,6 +121,7 @@ extern unsigned long get_wchan(struct task_struct *p); #define KSTK_ESP(task) (task_pt_regs(task)->sp) #define cpu_relax() do { } while (0) +#define cpu_relax_lowlatency() cpu_relax() extern const struct seq_operations cpuinfo_op; diff --git a/arch/cris/include/asm/processor.h b/arch/cris/include/asm/processor.h index 15b815d..862126b 100644 --- a/arch/cris/include/asm/processor.h +++ b/arch/cris/include/asm/processor.h @@ -63,6 +63,7 @@ static inline void release_thread(struct task_struct *dead_task) #define init_stack (init_thread_union.stack) #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() void default_idle(void); diff --git a/arch/hexagon/include/asm/processor.h b/arch/hexagon/include/asm/processor.h index 45a8254..d850113 100644 --- a/arch/hexagon/include/asm/processor.h +++ b/arch/hexagon/include/asm/processor.h @@ -56,6 +56,7 @@ struct thread_struct { } #define cpu_relax() __vmyield() +#define cpu_relax_lowlatency() cpu_relax() /* * Decides where the kernel will search for a free chunk of vm space during diff --git a/arch/ia64/include/asm/processor.h b/arch/ia64/include/asm/processor.h index efd1b92..c736713 100644 --- a/arch/ia64/include/asm/processor.h +++ b/arch/ia64/include/asm/processor.h @@ -548,6 +548,7 @@ ia64_eoi (void) } #define cpu_relax() ia64_hint(ia64_hint_pause) +#define cpu_relax_lowlatency() cpu_relax() static inline int ia64_get_irr(unsigned int vector) diff --git a/arch/m32r/include/asm/processor.h b/arch/m32r/include/asm/processor.h index 5767367..9f8fd9b 100644 --- a/arch/m32r/include/asm/processor.h +++ b/arch/m32r/include/asm/processor.h @@ -133,5 +133,6 @@ unsigned long get_wchan(struct task_struct *p); #define KSTK_ESP(tsk) ((tsk)->thread.sp) #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() #endif /* _ASM_M32R_PROCESSOR_H */ diff --git a/arch/m68k/include/asm/processor.h b/arch/m68k/include/asm/processor.h index b0768a6..20dda1d 100644 --- a/arch/m68k/include/asm/processor.h +++ b/arch/m68k/include/asm/processor.h @@ -176,5 +176,6 @@ unsigned long get_wchan(struct task_struct *p); #define task_pt_regs(tsk) ((struct pt_regs *) ((tsk)->thread.esp0)) #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() #endif diff --git a/arch/metag/include/asm/processor.h b/arch/metag/include/asm/processor.h index a8a3747..881071c 100644 --- a/arch/metag/include/asm/processor.h +++ b/arch/metag/include/asm/processor.h @@ -155,6 +155,7 @@ unsigned long get_wchan(struct task_struct *p); #define user_stack_pointer(regs) ((regs)->ctx.AX[0].U0) #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() extern void setup_priv(void); diff --git a/arch/microblaze/include/asm/processor.h b/arch/microblaze/include/asm/processor.h index 9d31b05..497a988 100644 --- a/arch/microblaze/include/asm/processor.h +++ b/arch/microblaze/include/asm/processor.h @@ -22,6 +22,7 @@ extern const struct seq_operations cpuinfo_op; # define cpu_relax() barrier() +# define cpu_relax_lowlatency() cpu_relax() #define task_pt_regs(tsk) \ (((struct pt_regs *)(THREAD_SIZE + task_stack_page(tsk))) - 1) diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h index ad70cba..d5098bc 100644 --- a/arch/mips/include/asm/processor.h +++ b/arch/mips/include/asm/processor.h @@ -367,6 +367,7 @@ unsigned long get_wchan(struct task_struct *p); #define KSTK_STATUS(tsk) (task_pt_regs(tsk)->cp0_status) #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() /* * Return_address is a replacement for __builtin_return_address(count) diff --git a/arch/mn10300/include/asm/processor.h b/arch/mn10300/include/asm/processor.h index 8b80b19..769d5ed 100644 --- a/arch/mn10300/include/asm/processor.h +++ b/arch/mn10300/include/asm/processor.h @@ -68,7 +68,9 @@ extern struct mn10300_cpuinfo cpu_data[]; extern void identify_cpu(struct mn10300_cpuinfo *); extern void print_cpu_info(struct mn10300_cpuinfo *); extern void dodgy_tsc(void); + #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() /* * User space process size: 1.75GB (default). diff --git a/arch/openrisc/include/asm/processor.h b/arch/openrisc/include/asm/processor.h index cab746f..4d235e3 100644 --- a/arch/openrisc/include/asm/processor.h +++ b/arch/openrisc/include/asm/processor.h @@ -101,6 +101,7 @@ extern unsigned long thread_saved_pc(struct task_struct *t); #define init_stack (init_thread_union.stack) #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() #endif /* __ASSEMBLY__ */ #endif /* __ASM_OPENRISC_PROCESSOR_H */ diff --git a/arch/parisc/include/asm/processor.h b/arch/parisc/include/asm/processor.h index d951c96..689a8ad 100644 --- a/arch/parisc/include/asm/processor.h +++ b/arch/parisc/include/asm/processor.h @@ -338,6 +338,7 @@ extern unsigned long get_wchan(struct task_struct *p); #define KSTK_ESP(tsk) ((tsk)->thread.regs.gr[30]) #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() /* Used as a macro to identify the combined VIPT/PIPT cached * CPUs which require a guarantee of coherency (no inequivalent diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h index 6d59072..dda7ac4 100644 --- a/arch/powerpc/include/asm/processor.h +++ b/arch/powerpc/include/asm/processor.h @@ -400,6 +400,8 @@ static inline unsigned long __pack_fe01(unsigned int fpmode) #define cpu_relax() barrier() #endif +#define cpu_relax_lowlatency() cpu_relax() + /* Check that a certain kernel stack pointer is valid in task_struct p */ int validate_sp(unsigned long sp, struct task_struct *p, unsigned long nbytes); diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h index 6f02d45..e568fc8 100644 --- a/arch/s390/include/asm/processor.h +++ b/arch/s390/include/asm/processor.h @@ -217,7 +217,7 @@ static inline void cpu_relax(void) barrier(); } -#define arch_mutex_cpu_relax() barrier() +#define cpu_relax_lowlatency() barrier() static inline void psw_set_key(unsigned int key) { diff --git a/arch/score/include/asm/processor.h b/arch/score/include/asm/processor.h index d9a922d..851f441 100644 --- a/arch/score/include/asm/processor.h +++ b/arch/score/include/asm/processor.h @@ -24,6 +24,7 @@ extern unsigned long get_wchan(struct task_struct *p); #define current_text_addr() ({ __label__ _l; _l: &&_l; }) #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() #define release_thread(thread) do {} while (0) /* diff --git a/arch/sh/include/asm/processor.h b/arch/sh/include/asm/processor.h index 5448f9b..1506897 100644 --- a/arch/sh/include/asm/processor.h +++ b/arch/sh/include/asm/processor.h @@ -97,6 +97,7 @@ extern struct sh_cpuinfo cpu_data[]; #define cpu_sleep() __asm__ __volatile__ ("sleep" : : : "memory") #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() void default_idle(void); void stop_this_cpu(void *); diff --git a/arch/sparc/include/asm/processor_32.h b/arch/sparc/include/asm/processor_32.h index a564817..812fd08 100644 --- a/arch/sparc/include/asm/processor_32.h +++ b/arch/sparc/include/asm/processor_32.h @@ -119,6 +119,8 @@ extern struct task_struct *last_task_used_math; int do_mathemu(struct pt_regs *regs, struct task_struct *fpt); #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() + extern void (*sparc_idle)(void); #endif diff --git a/arch/sparc/include/asm/processor_64.h b/arch/sparc/include/asm/processor_64.h index 7028fe1..6924bde 100644 --- a/arch/sparc/include/asm/processor_64.h +++ b/arch/sparc/include/asm/processor_64.h @@ -216,6 +216,7 @@ unsigned long get_wchan(struct task_struct *task); "nop\n\t" \ ".previous" \ ::: "memory") +#define cpu_relax_lowlatency() cpu_relax() /* Prefetch support. This is tuned for UltraSPARC-III and later. * UltraSPARC-I will treat these as nops, and UltraSPARC-II has diff --git a/arch/tile/include/asm/processor.h b/arch/tile/include/asm/processor.h index 4232363..dd4f9f1 100644 --- a/arch/tile/include/asm/processor.h +++ b/arch/tile/include/asm/processor.h @@ -266,6 +266,8 @@ static inline void cpu_relax(void) barrier(); } +#define cpu_relax_lowlatency() cpu_relax() + /* Info on this processor (see fs/proc/cpuinfo.c) */ struct seq_operations; extern const struct seq_operations cpuinfo_op; diff --git a/arch/unicore32/include/asm/processor.h b/arch/unicore32/include/asm/processor.h index 4eaa421..8d21b7a 100644 --- a/arch/unicore32/include/asm/processor.h +++ b/arch/unicore32/include/asm/processor.h @@ -71,6 +71,7 @@ extern void release_thread(struct task_struct *); unsigned long get_wchan(struct task_struct *p); #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() #define task_pt_regs(p) \ ((struct pt_regs *)(THREAD_START_SP + task_stack_page(p)) - 1) diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h index 5c7198c..0f4460b 100644 --- a/arch/x86/include/asm/barrier.h +++ b/arch/x86/include/asm/barrier.h @@ -99,7 +99,7 @@ #if defined(CONFIG_X86_PPRO_FENCE) /* - * For either of these options x86 doesn't have a strong TSO memory + * For this option x86 doesn't have a strong TSO memory * model and we should fall back to full barriers. */ diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index a4ea023..32cc237 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -696,6 +696,8 @@ static inline void cpu_relax(void) rep_nop(); } +#define cpu_relax_lowlatency() cpu_relax() + /* Stop speculative execution and prefetching of modified code. */ static inline void sync_core(void) { diff --git a/arch/x86/include/asm/qrwlock.h b/arch/x86/include/asm/qrwlock.h index 70f46f0..ae0e241 100644 --- a/arch/x86/include/asm/qrwlock.h +++ b/arch/x86/include/asm/qrwlock.h @@ -3,7 +3,7 @@ #include <asm-generic/qrwlock_types.h> -#if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE) +#ifndef CONFIG_X86_PPRO_FENCE #define queue_write_unlock queue_write_unlock static inline void queue_write_unlock(struct qrwlock *lock) { diff --git a/arch/x86/um/asm/processor.h b/arch/x86/um/asm/processor.h index 04f82e0..2a206d2 100644 --- a/arch/x86/um/asm/processor.h +++ b/arch/x86/um/asm/processor.h @@ -25,7 +25,8 @@ static inline void rep_nop(void) __asm__ __volatile__("rep;nop": : :"memory"); } -#define cpu_relax() rep_nop() +#define cpu_relax() rep_nop() +#define cpu_relax_lowlatency() cpu_relax() #include <asm/processor-generic.h> diff --git a/arch/xtensa/include/asm/processor.h b/arch/xtensa/include/asm/processor.h index abb5970..b61bdf0 100644 --- a/arch/xtensa/include/asm/processor.h +++ b/arch/xtensa/include/asm/processor.h @@ -182,6 +182,7 @@ extern unsigned long get_wchan(struct task_struct *p); #define KSTK_ESP(tsk) (task_pt_regs(tsk)->areg[1]) #define cpu_relax() barrier() +#define cpu_relax_lowlatency() cpu_relax() /* Special register access. */ diff --git a/include/linux/mutex.h b/include/linux/mutex.h index 42aa9b9..8d5535c 100644 --- a/include/linux/mutex.h +++ b/include/linux/mutex.h @@ -176,8 +176,4 @@ extern void mutex_unlock(struct mutex *lock); extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock); -#ifndef arch_mutex_cpu_relax -# define arch_mutex_cpu_relax() cpu_relax() -#endif - #endif /* __LINUX_MUTEX_H */ diff --git a/include/linux/rtmutex.h b/include/linux/rtmutex.h index 3aed8d7..1abba5c 100644 --- a/include/linux/rtmutex.h +++ b/include/linux/rtmutex.h @@ -90,11 +90,9 @@ extern void __rt_mutex_init(struct rt_mutex *lock, const char *name); extern void rt_mutex_destroy(struct rt_mutex *lock); extern void rt_mutex_lock(struct rt_mutex *lock); -extern int rt_mutex_lock_interruptible(struct rt_mutex *lock, - int detect_deadlock); +extern int rt_mutex_lock_interruptible(struct rt_mutex *lock); extern int rt_mutex_timed_lock(struct rt_mutex *lock, - struct hrtimer_sleeper *timeout, - int detect_deadlock); + struct hrtimer_sleeper *timeout); extern int rt_mutex_trylock(struct rt_mutex *lock); diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h index 535f158..8cf3503 100644 --- a/include/linux/seqlock.h +++ b/include/linux/seqlock.h @@ -164,8 +164,6 @@ static inline unsigned read_seqcount_begin(const seqcount_t *s) static inline unsigned raw_seqcount_begin(const seqcount_t *s) { unsigned ret = ACCESS_ONCE(s->sequence); - - seqcount_lockdep_reader_access(s); smp_rmb(); return ret & ~1; } diff --git a/kernel/futex.c b/kernel/futex.c index b632b5f..d3a9d94 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -792,94 +792,91 @@ void exit_pi_state_list(struct task_struct *curr) * [10] There is no transient state which leaves owner and user space * TID out of sync. */ -static int -lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, - union futex_key *key, struct futex_pi_state **ps) + +/* + * Validate that the existing waiter has a pi_state and sanity check + * the pi_state against the user space value. If correct, attach to + * it. + */ +static int attach_to_pi_state(u32 uval, struct futex_pi_state *pi_state, + struct futex_pi_state **ps) { - struct futex_pi_state *pi_state = NULL; - struct futex_q *this, *next; - struct task_struct *p; pid_t pid = uval & FUTEX_TID_MASK; - plist_for_each_entry_safe(this, next, &hb->chain, list) { - if (match_futex(&this->key, key)) { - /* - * Sanity check the waiter before increasing - * the refcount and attaching to it. - */ - pi_state = this->pi_state; - /* - * Userspace might have messed up non-PI and - * PI futexes [3] - */ - if (unlikely(!pi_state)) - return -EINVAL; + /* + * Userspace might have messed up non-PI and PI futexes [3] + */ + if (unlikely(!pi_state)) + return -EINVAL; - WARN_ON(!atomic_read(&pi_state->refcount)); + WARN_ON(!atomic_read(&pi_state->refcount)); + /* + * Handle the owner died case: + */ + if (uval & FUTEX_OWNER_DIED) { + /* + * exit_pi_state_list sets owner to NULL and wakes the + * topmost waiter. The task which acquires the + * pi_state->rt_mutex will fixup owner. + */ + if (!pi_state->owner) { /* - * Handle the owner died case: + * No pi state owner, but the user space TID + * is not 0. Inconsistent state. [5] */ - if (uval & FUTEX_OWNER_DIED) { - /* - * exit_pi_state_list sets owner to NULL and - * wakes the topmost waiter. The task which - * acquires the pi_state->rt_mutex will fixup - * owner. - */ - if (!pi_state->owner) { - /* - * No pi state owner, but the user - * space TID is not 0. Inconsistent - * state. [5] - */ - if (pid) - return -EINVAL; - /* - * Take a ref on the state and - * return. [4] - */ - goto out_state; - } - - /* - * If TID is 0, then either the dying owner - * has not yet executed exit_pi_state_list() - * or some waiter acquired the rtmutex in the - * pi state, but did not yet fixup the TID in - * user space. - * - * Take a ref on the state and return. [6] - */ - if (!pid) - goto out_state; - } else { - /* - * If the owner died bit is not set, - * then the pi_state must have an - * owner. [7] - */ - if (!pi_state->owner) - return -EINVAL; - } - + if (pid) + return -EINVAL; /* - * Bail out if user space manipulated the - * futex value. If pi state exists then the - * owner TID must be the same as the user - * space TID. [9/10] + * Take a ref on the state and return success. [4] */ - if (pid != task_pid_vnr(pi_state->owner)) - return -EINVAL; - - out_state: - atomic_inc(&pi_state->refcount); - *ps = pi_state; - return 0; + goto out_state; } + + /* + * If TID is 0, then either the dying owner has not + * yet executed exit_pi_state_list() or some waiter + * acquired the rtmutex in the pi state, but did not + * yet fixup the TID in user space. + * + * Take a ref on the state and return success. [6] + */ + if (!pid) + goto out_state; + } else { + /* + * If the owner died bit is not set, then the pi_state + * must have an owner. [7] + */ + if (!pi_state->owner) + return -EINVAL; } /* + * Bail out if user space manipulated the futex value. If pi + * state exists then the owner TID must be the same as the + * user space TID. [9/10] + */ + if (pid != task_pid_vnr(pi_state->owner)) + return -EINVAL; +out_state: + atomic_inc(&pi_state->refcount); + *ps = pi_state; + return 0; +} + +/* + * Lookup the task for the TID provided from user space and attach to + * it after doing proper sanity checks. + */ +static int attach_to_pi_owner(u32 uval, union futex_key *key, + struct futex_pi_state **ps) +{ + pid_t pid = uval & FUTEX_TID_MASK; + struct futex_pi_state *pi_state; + struct task_struct *p; + + /* * We are the first waiter - try to look up the real owner and attach * the new pi_state to it, but bail out when TID = 0 [1] */ @@ -920,7 +917,7 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, pi_state = alloc_pi_state(); /* - * Initialize the pi_mutex in locked state and make 'p' + * Initialize the pi_mutex in locked state and make @p * the owner of it: */ rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p); @@ -940,6 +937,36 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, return 0; } +static int lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, + union futex_key *key, struct futex_pi_state **ps) +{ + struct futex_q *match = futex_top_waiter(hb, key); + + /* + * If there is a waiter on that futex, validate it and + * attach to the pi_state when the validation succeeds. + */ + if (match) + return attach_to_pi_state(uval, match->pi_state, ps); + + /* + * We are the first waiter - try to look up the owner based on + * @uval and attach to it. + */ + return attach_to_pi_owner(uval, key, ps); +} + +static int lock_pi_update_atomic(u32 __user *uaddr, u32 uval, u32 newval) +{ + u32 uninitialized_var(curval); + + if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))) + return -EFAULT; + + /*If user space value changed, let the caller retry */ + return curval != uval ? -EAGAIN : 0; +} + /** * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex * @uaddr: the pi futex user address @@ -963,113 +990,69 @@ static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb, struct futex_pi_state **ps, struct task_struct *task, int set_waiters) { - int lock_taken, ret, force_take = 0; - u32 uval, newval, curval, vpid = task_pid_vnr(task); - -retry: - ret = lock_taken = 0; + u32 uval, newval, vpid = task_pid_vnr(task); + struct futex_q *match; + int ret; /* - * To avoid races, we attempt to take the lock here again - * (by doing a 0 -> TID atomic cmpxchg), while holding all - * the locks. It will most likely not succeed. + * Read the user space value first so we can validate a few + * things before proceeding further. */ - newval = vpid; - if (set_waiters) - newval |= FUTEX_WAITERS; - - if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, 0, newval))) + if (get_futex_value_locked(&uval, uaddr)) return -EFAULT; /* * Detect deadlocks. */ - if ((unlikely((curval & FUTEX_TID_MASK) == vpid))) + if ((unlikely((uval & FUTEX_TID_MASK) == vpid))) return -EDEADLK; /* - * Surprise - we got the lock, but we do not trust user space at all. - */ - if (unlikely(!curval)) { - /* - * We verify whether there is kernel state for this - * futex. If not, we can safely assume, that the 0 -> - * TID transition is correct. If state exists, we do - * not bother to fixup the user space state as it was - * corrupted already. - */ - return futex_top_waiter(hb, key) ? -EINVAL : 1; - } - - uval = curval; - - /* - * Set the FUTEX_WAITERS flag, so the owner will know it has someone - * to wake at the next unlock. + * Lookup existing state first. If it exists, try to attach to + * its pi_state. */ - newval = curval | FUTEX_WAITERS; + match = futex_top_waiter(hb, key); + if (match) + return attach_to_pi_state(uval, match->pi_state, ps); /* - * Should we force take the futex? See below. + * No waiter and user TID is 0. We are here because the + * waiters or the owner died bit is set or called from + * requeue_cmp_pi or for whatever reason something took the + * syscall. */ - if (unlikely(force_take)) { + if (!(uval & FUTEX_TID_MASK)) { /* - * Keep the OWNER_DIED and the WAITERS bit and set the - * new TID value. + * We take over the futex. No other waiters and the user space + * TID is 0. We preserve the owner died bit. */ - newval = (curval & ~FUTEX_TID_MASK) | vpid; - force_take = 0; - lock_taken = 1; - } + newval = uval & FUTEX_OWNER_DIED; + newval |= vpid; - if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))) - return -EFAULT; - if (unlikely(curval != uval)) - goto retry; + /* The futex requeue_pi code can enforce the waiters bit */ + if (set_waiters) + newval |= FUTEX_WAITERS; + + ret = lock_pi_update_atomic(uaddr, uval, newval); + /* If the take over worked, return 1 */ + return ret < 0 ? ret : 1; + } /* - * We took the lock due to forced take over. + * First waiter. Set the waiters bit before attaching ourself to + * the owner. If owner tries to unlock, it will be forced into + * the kernel and blocked on hb->lock. */ - if (unlikely(lock_taken)) - return 1; - + newval = uval | FUTEX_WAITERS; + ret = lock_pi_update_atomic(uaddr, uval, newval); + if (ret) + return ret; /* - * We dont have the lock. Look up the PI state (or create it if - * we are the first waiter): + * If the update of the user space value succeeded, we try to + * attach to the owner. If that fails, no harm done, we only + * set the FUTEX_WAITERS bit in the user space variable. */ - ret = lookup_pi_state(uval, hb, key, ps); - - if (unlikely(ret)) { - switch (ret) { - case -ESRCH: - /* - * We failed to find an owner for this - * futex. So we have no pi_state to block - * on. This can happen in two cases: - * - * 1) The owner died - * 2) A stale FUTEX_WAITERS bit - * - * Re-read the futex value. - */ - if (get_futex_value_locked(&curval, uaddr)) - return -EFAULT; - - /* - * If the owner died or we have a stale - * WAITERS bit the owner TID in the user space - * futex is 0. - */ - if (!(curval & FUTEX_TID_MASK)) { - force_take = 1; - goto retry; - } - default: - break; - } - } - - return ret; + return attach_to_pi_owner(uval, key, ps); } /** @@ -1186,22 +1169,6 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this) return 0; } -static int unlock_futex_pi(u32 __user *uaddr, u32 uval) -{ - u32 uninitialized_var(oldval); - - /* - * There is no waiter, so we unlock the futex. The owner died - * bit has not to be preserved here. We are the owner: - */ - if (cmpxchg_futex_value_locked(&oldval, uaddr, uval, 0)) - return -EFAULT; - if (oldval != uval) - return -EAGAIN; - - return 0; -} - /* * Express the locking dependencies for lockdep: */ @@ -1659,7 +1626,12 @@ retry_private: goto retry; goto out; case -EAGAIN: - /* The owner was exiting, try again. */ + /* + * Two reasons for this: + * - Owner is exiting and we just wait for the + * exit to complete. + * - The user space value changed. + */ double_unlock_hb(hb1, hb2); hb_waiters_dec(hb2); put_futex_key(&key2); @@ -1718,7 +1690,7 @@ retry_private: this->pi_state = pi_state; ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex, this->rt_waiter, - this->task, 1); + this->task); if (ret == 1) { /* We got the lock. */ requeue_pi_wake_futex(this, &key2, hb2); @@ -2316,8 +2288,10 @@ retry_private: goto uaddr_faulted; case -EAGAIN: /* - * Task is exiting and we just wait for the - * exit to complete. + * Two reasons for this: + * - Task is exiting and we just wait for the + * exit to complete. + * - The user space value changed. */ queue_unlock(hb); put_futex_key(&q.key); @@ -2337,9 +2311,9 @@ retry_private: /* * Block on the PI mutex: */ - if (!trylock) - ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1); - else { + if (!trylock) { + ret = rt_mutex_timed_futex_lock(&q.pi_state->pi_mutex, to); + } else { ret = rt_mutex_trylock(&q.pi_state->pi_mutex); /* Fixup the trylock return value: */ ret = ret ? 0 : -EWOULDBLOCK; @@ -2401,10 +2375,10 @@ uaddr_faulted: */ static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags) { - struct futex_hash_bucket *hb; - struct futex_q *this, *next; + u32 uninitialized_var(curval), uval, vpid = task_pid_vnr(current); union futex_key key = FUTEX_KEY_INIT; - u32 uval, vpid = task_pid_vnr(current); + struct futex_hash_bucket *hb; + struct futex_q *match; int ret; retry: @@ -2417,57 +2391,47 @@ retry: return -EPERM; ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, VERIFY_WRITE); - if (unlikely(ret != 0)) - goto out; + if (ret) + return ret; hb = hash_futex(&key); spin_lock(&hb->lock); /* - * To avoid races, try to do the TID -> 0 atomic transition - * again. If it succeeds then we can return without waking - * anyone else up. We only try this if neither the waiters nor - * the owner died bit are set. - */ - if (!(uval & ~FUTEX_TID_MASK) && - cmpxchg_futex_value_locked(&uval, uaddr, vpid, 0)) - goto pi_faulted; - /* - * Rare case: we managed to release the lock atomically, - * no need to wake anyone else up: - */ - if (unlikely(uval == vpid)) - goto out_unlock; - - /* - * Ok, other tasks may need to be woken up - check waiters - * and do the wakeup if necessary: + * Check waiters first. We do not trust user space values at + * all and we at least want to know if user space fiddled + * with the futex value instead of blindly unlocking. */ - plist_for_each_entry_safe(this, next, &hb->chain, list) { - if (!match_futex (&this->key, &key)) - continue; - ret = wake_futex_pi(uaddr, uval, this); + match = futex_top_waiter(hb, &key); + if (match) { + ret = wake_futex_pi(uaddr, uval, match); /* - * The atomic access to the futex value - * generated a pagefault, so retry the - * user-access and the wakeup: + * The atomic access to the futex value generated a + * pagefault, so retry the user-access and the wakeup: */ if (ret == -EFAULT) goto pi_faulted; goto out_unlock; } + /* - * No waiters - kernel unlocks the futex: + * We have no kernel internal state, i.e. no waiters in the + * kernel. Waiters which are about to queue themselves are stuck + * on hb->lock. So we can safely ignore them. We do neither + * preserve the WAITERS bit not the OWNER_DIED one. We are the + * owner. */ - ret = unlock_futex_pi(uaddr, uval); - if (ret == -EFAULT) + if (cmpxchg_futex_value_locked(&curval, uaddr, uval, 0)) goto pi_faulted; + /* + * If uval has changed, let user space handle it. + */ + ret = (curval == uval) ? 0 : -EAGAIN; + out_unlock: spin_unlock(&hb->lock); put_futex_key(&key); - -out: return ret; pi_faulted: @@ -2669,7 +2633,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, */ WARN_ON(!q.pi_state); pi_mutex = &q.pi_state->pi_mutex; - ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1); + ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter); debug_rt_mutex_free_waiter(&rt_waiter); spin_lock(q.lock_ptr); diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index d24e433..88d0d44 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -384,7 +384,9 @@ static void print_lockdep_off(const char *bug_msg) { printk(KERN_DEBUG "%s\n", bug_msg); printk(KERN_DEBUG "turning off the locking correctness validator.\n"); +#ifdef CONFIG_LOCK_STAT printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n"); +#endif } static int save_trace(struct stack_trace *trace) diff --git a/kernel/locking/mcs_spinlock.c b/kernel/locking/mcs_spinlock.c index be9ee15..9887a90 100644 --- a/kernel/locking/mcs_spinlock.c +++ b/kernel/locking/mcs_spinlock.c @@ -1,6 +1,4 @@ - #include <linux/percpu.h> -#include <linux/mutex.h> #include <linux/sched.h> #include "mcs_spinlock.h" @@ -79,7 +77,7 @@ osq_wait_next(struct optimistic_spin_queue *lock, break; } - arch_mutex_cpu_relax(); + cpu_relax_lowlatency(); } return next; @@ -120,7 +118,7 @@ bool osq_lock(struct optimistic_spin_queue *lock) if (need_resched()) goto unqueue; - arch_mutex_cpu_relax(); + cpu_relax_lowlatency(); } return true; @@ -146,7 +144,7 @@ unqueue: if (smp_load_acquire(&node->locked)) return true; - arch_mutex_cpu_relax(); + cpu_relax_lowlatency(); /* * Or we race against a concurrent unqueue()'s step-B, in which diff --git a/kernel/locking/mcs_spinlock.h b/kernel/locking/mcs_spinlock.h index 74356dc..23e89c5 100644 --- a/kernel/locking/mcs_spinlock.h +++ b/kernel/locking/mcs_spinlock.h @@ -27,7 +27,7 @@ struct mcs_spinlock { #define arch_mcs_spin_lock_contended(l) \ do { \ while (!(smp_load_acquire(l))) \ - arch_mutex_cpu_relax(); \ + cpu_relax_lowlatency(); \ } while (0) #endif @@ -104,7 +104,7 @@ void mcs_spin_unlock(struct mcs_spinlock **lock, struct mcs_spinlock *node) return; /* Wait until the next pointer is set */ while (!(next = ACCESS_ONCE(node->next))) - arch_mutex_cpu_relax(); + cpu_relax_lowlatency(); } /* Pass lock to next waiter. */ diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index acca2c1..ae712b2 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -46,12 +46,6 @@ # include <asm/mutex.h> #endif -/* - * A negative mutex count indicates that waiters are sleeping waiting for the - * mutex. - */ -#define MUTEX_SHOW_NO_WAITER(mutex) (atomic_read(&(mutex)->count) >= 0) - void __mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key) { @@ -152,7 +146,7 @@ int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner) if (need_resched()) break; - arch_mutex_cpu_relax(); + cpu_relax_lowlatency(); } rcu_read_unlock(); @@ -388,12 +382,10 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, /* * Optimistic spinning. * - * We try to spin for acquisition when we find that there are no - * pending waiters and the lock owner is currently running on a - * (different) CPU. - * - * The rationale is that if the lock owner is running, it is likely to - * release the lock soon. + * We try to spin for acquisition when we find that the lock owner + * is currently running on a (different) CPU and while we don't + * need to reschedule. The rationale is that if the lock owner is + * running, it is likely to release the lock soon. * * Since this needs the lock owner, and this mutex implementation * doesn't track the owner atomically in the lock field, we need to @@ -440,7 +432,8 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, if (owner && !mutex_spin_on_owner(lock, owner)) break; - if ((atomic_read(&lock->count) == 1) && + /* Try to acquire the mutex if it is unlocked. */ + if (!mutex_is_locked(lock) && (atomic_cmpxchg(&lock->count, 1, 0) == 1)) { lock_acquired(&lock->dep_map, ip); if (use_ww_ctx) { @@ -471,7 +464,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass, * memory barriers as we'll eventually observe the right * values at the cost of a few extra spins. */ - arch_mutex_cpu_relax(); + cpu_relax_lowlatency(); } osq_unlock(&lock->osq); slowpath: @@ -485,8 +478,11 @@ slowpath: #endif spin_lock_mutex(&lock->wait_lock, flags); - /* once more, can we acquire the lock? */ - if (MUTEX_SHOW_NO_WAITER(lock) && (atomic_xchg(&lock->count, 0) == 1)) + /* + * Once more, try to acquire the lock. Only try-lock the mutex if + * it is unlocked to reduce unnecessary xchg() operations. + */ + if (!mutex_is_locked(lock) && (atomic_xchg(&lock->count, 0) == 1)) goto skip_wait; debug_mutex_lock_common(lock, &waiter); @@ -506,9 +502,10 @@ slowpath: * it's unlocked. Later on, if we sleep, this is the * operation that gives us the lock. We xchg it to -1, so * that when we release the lock, we properly wake up the - * other waiters: + * other waiters. We only attempt the xchg if the count is + * non-negative in order to avoid unnecessary xchg operations: */ - if (MUTEX_SHOW_NO_WAITER(lock) && + if (atomic_read(&lock->count) >= 0 && (atomic_xchg(&lock->count, -1) == 1)) break; @@ -823,6 +820,10 @@ static inline int __mutex_trylock_slowpath(atomic_t *lock_count) unsigned long flags; int prev; + /* No need to trylock if the mutex is locked. */ + if (mutex_is_locked(lock)) + return 0; + spin_lock_mutex(&lock->wait_lock, flags); prev = atomic_xchg(&lock->count, -1); diff --git a/kernel/locking/qrwlock.c b/kernel/locking/qrwlock.c index fb5b8ac..f956ede 100644 --- a/kernel/locking/qrwlock.c +++ b/kernel/locking/qrwlock.c @@ -20,7 +20,6 @@ #include <linux/cpumask.h> #include <linux/percpu.h> #include <linux/hardirq.h> -#include <linux/mutex.h> #include <asm/qrwlock.h> /** @@ -35,7 +34,7 @@ static __always_inline void rspin_until_writer_unlock(struct qrwlock *lock, u32 cnts) { while ((cnts & _QW_WMASK) == _QW_LOCKED) { - arch_mutex_cpu_relax(); + cpu_relax_lowlatency(); cnts = smp_load_acquire((u32 *)&lock->cnts); } } @@ -75,7 +74,7 @@ void queue_read_lock_slowpath(struct qrwlock *lock) * to make sure that the write lock isn't taken. */ while (atomic_read(&lock->cnts) & _QW_WMASK) - arch_mutex_cpu_relax(); + cpu_relax_lowlatency(); cnts = atomic_add_return(_QR_BIAS, &lock->cnts) - _QR_BIAS; rspin_until_writer_unlock(lock, cnts); @@ -114,7 +113,7 @@ void queue_write_lock_slowpath(struct qrwlock *lock) cnts | _QW_WAITING) == cnts)) break; - arch_mutex_cpu_relax(); + cpu_relax_lowlatency(); } /* When no more readers, set the locked flag */ @@ -125,7 +124,7 @@ void queue_write_lock_slowpath(struct qrwlock *lock) _QW_LOCKED) == _QW_WAITING)) break; - arch_mutex_cpu_relax(); + cpu_relax_lowlatency(); } unlock: arch_spin_unlock(&lock->lock); diff --git a/kernel/locking/rtmutex-debug.c b/kernel/locking/rtmutex-debug.c index 49b2ed3..62b6cee 100644 --- a/kernel/locking/rtmutex-debug.c +++ b/kernel/locking/rtmutex-debug.c @@ -66,12 +66,13 @@ void rt_mutex_debug_task_free(struct task_struct *task) * the deadlock. We print when we return. act_waiter can be NULL in * case of a remove waiter operation. */ -void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *act_waiter, +void debug_rt_mutex_deadlock(enum rtmutex_chainwalk chwalk, + struct rt_mutex_waiter *act_waiter, struct rt_mutex *lock) { struct task_struct *task; - if (!debug_locks || detect || !act_waiter) + if (!debug_locks || chwalk == RT_MUTEX_FULL_CHAINWALK || !act_waiter) return; task = rt_mutex_owner(act_waiter->lock); diff --git a/kernel/locking/rtmutex-debug.h b/kernel/locking/rtmutex-debug.h index ab29b6a..d0519c3 100644 --- a/kernel/locking/rtmutex-debug.h +++ b/kernel/locking/rtmutex-debug.h @@ -20,14 +20,15 @@ extern void debug_rt_mutex_unlock(struct rt_mutex *lock); extern void debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner); extern void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock); -extern void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *waiter, +extern void debug_rt_mutex_deadlock(enum rtmutex_chainwalk chwalk, + struct rt_mutex_waiter *waiter, struct rt_mutex *lock); extern void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter); # define debug_rt_mutex_reset_waiter(w) \ do { (w)->deadlock_lock = NULL; } while (0) -static inline int debug_rt_mutex_detect_deadlock(struct rt_mutex_waiter *waiter, - int detect) +static inline bool debug_rt_mutex_detect_deadlock(struct rt_mutex_waiter *waiter, + enum rtmutex_chainwalk walk) { return (waiter != NULL); } diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index fc60594..a0ea2a1 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -308,6 +308,32 @@ static void rt_mutex_adjust_prio(struct task_struct *task) } /* + * Deadlock detection is conditional: + * + * If CONFIG_DEBUG_RT_MUTEXES=n, deadlock detection is only conducted + * if the detect argument is == RT_MUTEX_FULL_CHAINWALK. + * + * If CONFIG_DEBUG_RT_MUTEXES=y, deadlock detection is always + * conducted independent of the detect argument. + * + * If the waiter argument is NULL this indicates the deboost path and + * deadlock detection is disabled independent of the detect argument + * and the config settings. + */ +static bool rt_mutex_cond_detect_deadlock(struct rt_mutex_waiter *waiter, + enum rtmutex_chainwalk chwalk) +{ + /* + * This is just a wrapper function for the following call, + * because debug_rt_mutex_detect_deadlock() smells like a magic + * debug feature and I wanted to keep the cond function in the + * main source file along with the comments instead of having + * two of the same in the headers. + */ + return debug_rt_mutex_detect_deadlock(waiter, chwalk); +} + +/* * Max number of times we'll walk the boosting chain: */ int max_lock_depth = 1024; @@ -337,21 +363,65 @@ static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p) * @top_task: the current top waiter * * Returns 0 or -EDEADLK. + * + * Chain walk basics and protection scope + * + * [R] refcount on task + * [P] task->pi_lock held + * [L] rtmutex->wait_lock held + * + * Step Description Protected by + * function arguments: + * @task [R] + * @orig_lock if != NULL @top_task is blocked on it + * @next_lock Unprotected. Cannot be + * dereferenced. Only used for + * comparison. + * @orig_waiter if != NULL @top_task is blocked on it + * @top_task current, or in case of proxy + * locking protected by calling + * code + * again: + * loop_sanity_check(); + * retry: + * [1] lock(task->pi_lock); [R] acquire [P] + * [2] waiter = task->pi_blocked_on; [P] + * [3] check_exit_conditions_1(); [P] + * [4] lock = waiter->lock; [P] + * [5] if (!try_lock(lock->wait_lock)) { [P] try to acquire [L] + * unlock(task->pi_lock); release [P] + * goto retry; + * } + * [6] check_exit_conditions_2(); [P] + [L] + * [7] requeue_lock_waiter(lock, waiter); [P] + [L] + * [8] unlock(task->pi_lock); release [P] + * put_task_struct(task); release [R] + * [9] check_exit_conditions_3(); [L] + * [10] task = owner(lock); [L] + * get_task_struct(task); [L] acquire [R] + * lock(task->pi_lock); [L] acquire [P] + * [11] requeue_pi_waiter(tsk, waiters(lock));[P] + [L] + * [12] check_exit_conditions_4(); [P] + [L] + * [13] unlock(task->pi_lock); release [P] + * unlock(lock->wait_lock); release [L] + * goto again; */ static int rt_mutex_adjust_prio_chain(struct task_struct *task, - int deadlock_detect, + enum rtmutex_chainwalk chwalk, struct rt_mutex *orig_lock, struct rt_mutex *next_lock, struct rt_mutex_waiter *orig_waiter, struct task_struct *top_task) { - struct rt_mutex *lock; struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; - int detect_deadlock, ret = 0, depth = 0; + struct rt_mutex_waiter *prerequeue_top_waiter; + int ret = 0, depth = 0; + struct rt_mutex *lock; + bool detect_deadlock; unsigned long flags; + bool requeue = true; - detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter, - deadlock_detect); + detect_deadlock = rt_mutex_cond_detect_deadlock(orig_waiter, chwalk); /* * The (de)boosting is a step by step approach with a lot of @@ -360,6 +430,9 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, * carefully whether things change under us. */ again: + /* + * We limit the lock chain length for each invocation. + */ if (++depth > max_lock_depth) { static int prev_max; @@ -377,13 +450,28 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, return -EDEADLK; } + + /* + * We are fully preemptible here and only hold the refcount on + * @task. So everything can have changed under us since the + * caller or our own code below (goto retry/again) dropped all + * locks. + */ retry: /* - * Task can not go away as we did a get_task() before ! + * [1] Task cannot go away as we did a get_task() before ! */ raw_spin_lock_irqsave(&task->pi_lock, flags); + /* + * [2] Get the waiter on which @task is blocked on. + */ waiter = task->pi_blocked_on; + + /* + * [3] check_exit_conditions_1() protected by task->pi_lock. + */ + /* * Check whether the end of the boosting chain has been * reached or the state of the chain has changed while we @@ -421,20 +509,41 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, goto out_unlock_pi; /* * If deadlock detection is off, we stop here if we - * are not the top pi waiter of the task. + * are not the top pi waiter of the task. If deadlock + * detection is enabled we continue, but stop the + * requeueing in the chain walk. */ - if (!detect_deadlock && top_waiter != task_top_pi_waiter(task)) - goto out_unlock_pi; + if (top_waiter != task_top_pi_waiter(task)) { + if (!detect_deadlock) + goto out_unlock_pi; + else + requeue = false; + } } /* - * When deadlock detection is off then we check, if further - * priority adjustment is necessary. + * If the waiter priority is the same as the task priority + * then there is no further priority adjustment necessary. If + * deadlock detection is off, we stop the chain walk. If its + * enabled we continue, but stop the requeueing in the chain + * walk. */ - if (!detect_deadlock && waiter->prio == task->prio) - goto out_unlock_pi; + if (waiter->prio == task->prio) { + if (!detect_deadlock) + goto out_unlock_pi; + else + requeue = false; + } + /* + * [4] Get the next lock + */ lock = waiter->lock; + /* + * [5] We need to trylock here as we are holding task->pi_lock, + * which is the reverse lock order versus the other rtmutex + * operations. + */ if (!raw_spin_trylock(&lock->wait_lock)) { raw_spin_unlock_irqrestore(&task->pi_lock, flags); cpu_relax(); @@ -442,79 +551,180 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, } /* + * [6] check_exit_conditions_2() protected by task->pi_lock and + * lock->wait_lock. + * * Deadlock detection. If the lock is the same as the original * lock which caused us to walk the lock chain or if the * current lock is owned by the task which initiated the chain * walk, we detected a deadlock. */ if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { - debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock); + debug_rt_mutex_deadlock(chwalk, orig_waiter, lock); raw_spin_unlock(&lock->wait_lock); ret = -EDEADLK; goto out_unlock_pi; } - top_waiter = rt_mutex_top_waiter(lock); + /* + * If we just follow the lock chain for deadlock detection, no + * need to do all the requeue operations. To avoid a truckload + * of conditionals around the various places below, just do the + * minimum chain walk checks. + */ + if (!requeue) { + /* + * No requeue[7] here. Just release @task [8] + */ + raw_spin_unlock_irqrestore(&task->pi_lock, flags); + put_task_struct(task); + + /* + * [9] check_exit_conditions_3 protected by lock->wait_lock. + * If there is no owner of the lock, end of chain. + */ + if (!rt_mutex_owner(lock)) { + raw_spin_unlock(&lock->wait_lock); + return 0; + } + + /* [10] Grab the next task, i.e. owner of @lock */ + task = rt_mutex_owner(lock); + get_task_struct(task); + raw_spin_lock_irqsave(&task->pi_lock, flags); + + /* + * No requeue [11] here. We just do deadlock detection. + * + * [12] Store whether owner is blocked + * itself. Decision is made after dropping the locks + */ + next_lock = task_blocked_on_lock(task); + /* + * Get the top waiter for the next iteration + */ + top_waiter = rt_mutex_top_waiter(lock); + + /* [13] Drop locks */ + raw_spin_unlock_irqrestore(&task->pi_lock, flags); + raw_spin_unlock(&lock->wait_lock); + + /* If owner is not blocked, end of chain. */ + if (!next_lock) + goto out_put_task; + goto again; + } - /* Requeue the waiter */ + /* + * Store the current top waiter before doing the requeue + * operation on @lock. We need it for the boost/deboost + * decision below. + */ + prerequeue_top_waiter = rt_mutex_top_waiter(lock); + + /* [7] Requeue the waiter in the lock waiter list. */ rt_mutex_dequeue(lock, waiter); waiter->prio = task->prio; rt_mutex_enqueue(lock, waiter); - /* Release the task */ + /* [8] Release the task */ raw_spin_unlock_irqrestore(&task->pi_lock, flags); + put_task_struct(task); + + /* + * [9] check_exit_conditions_3 protected by lock->wait_lock. + * + * We must abort the chain walk if there is no lock owner even + * in the dead lock detection case, as we have nothing to + * follow here. This is the end of the chain we are walking. + */ if (!rt_mutex_owner(lock)) { /* - * If the requeue above changed the top waiter, then we need - * to wake the new top waiter up to try to get the lock. + * If the requeue [7] above changed the top waiter, + * then we need to wake the new top waiter up to try + * to get the lock. */ - - if (top_waiter != rt_mutex_top_waiter(lock)) + if (prerequeue_top_waiter != rt_mutex_top_waiter(lock)) wake_up_process(rt_mutex_top_waiter(lock)->task); raw_spin_unlock(&lock->wait_lock); - goto out_put_task; + return 0; } - put_task_struct(task); - /* Grab the next task */ + /* [10] Grab the next task, i.e. the owner of @lock */ task = rt_mutex_owner(lock); get_task_struct(task); raw_spin_lock_irqsave(&task->pi_lock, flags); + /* [11] requeue the pi waiters if necessary */ if (waiter == rt_mutex_top_waiter(lock)) { - /* Boost the owner */ - rt_mutex_dequeue_pi(task, top_waiter); + /* + * The waiter became the new top (highest priority) + * waiter on the lock. Replace the previous top waiter + * in the owner tasks pi waiters list with this waiter + * and adjust the priority of the owner. + */ + rt_mutex_dequeue_pi(task, prerequeue_top_waiter); rt_mutex_enqueue_pi(task, waiter); __rt_mutex_adjust_prio(task); - } else if (top_waiter == waiter) { - /* Deboost the owner */ + } else if (prerequeue_top_waiter == waiter) { + /* + * The waiter was the top waiter on the lock, but is + * no longer the top prority waiter. Replace waiter in + * the owner tasks pi waiters list with the new top + * (highest priority) waiter and adjust the priority + * of the owner. + * The new top waiter is stored in @waiter so that + * @waiter == @top_waiter evaluates to true below and + * we continue to deboost the rest of the chain. + */ rt_mutex_dequeue_pi(task, waiter); waiter = rt_mutex_top_waiter(lock); rt_mutex_enqueue_pi(task, waiter); __rt_mutex_adjust_prio(task); + } else { + /* + * Nothing changed. No need to do any priority + * adjustment. + */ } /* + * [12] check_exit_conditions_4() protected by task->pi_lock + * and lock->wait_lock. The actual decisions are made after we + * dropped the locks. + * * Check whether the task which owns the current lock is pi * blocked itself. If yes we store a pointer to the lock for * the lock chain change detection above. After we dropped * task->pi_lock next_lock cannot be dereferenced anymore. */ next_lock = task_blocked_on_lock(task); + /* + * Store the top waiter of @lock for the end of chain walk + * decision below. + */ + top_waiter = rt_mutex_top_waiter(lock); + /* [13] Drop the locks */ raw_spin_unlock_irqrestore(&task->pi_lock, flags); - - top_waiter = rt_mutex_top_waiter(lock); raw_spin_unlock(&lock->wait_lock); /* + * Make the actual exit decisions [12], based on the stored + * values. + * * We reached the end of the lock chain. Stop right here. No * point to go back just to figure that out. */ if (!next_lock) goto out_put_task; + /* + * If the current waiter is not the top waiter on the lock, + * then we can stop the chain walk here if we are not in full + * deadlock detection mode. + */ if (!detect_deadlock && waiter != top_waiter) goto out_put_task; @@ -533,76 +743,119 @@ static int rt_mutex_adjust_prio_chain(struct task_struct *task, * * Must be called with lock->wait_lock held. * - * @lock: the lock to be acquired. - * @task: the task which wants to acquire the lock - * @waiter: the waiter that is queued to the lock's wait list. (could be NULL) + * @lock: The lock to be acquired. + * @task: The task which wants to acquire the lock + * @waiter: The waiter that is queued to the lock's wait list if the + * callsite called task_blocked_on_lock(), otherwise NULL */ static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task, - struct rt_mutex_waiter *waiter) + struct rt_mutex_waiter *waiter) { + unsigned long flags; + /* - * We have to be careful here if the atomic speedups are - * enabled, such that, when - * - no other waiter is on the lock - * - the lock has been released since we did the cmpxchg - * the lock can be released or taken while we are doing the - * checks and marking the lock with RT_MUTEX_HAS_WAITERS. + * Before testing whether we can acquire @lock, we set the + * RT_MUTEX_HAS_WAITERS bit in @lock->owner. This forces all + * other tasks which try to modify @lock into the slow path + * and they serialize on @lock->wait_lock. + * + * The RT_MUTEX_HAS_WAITERS bit can have a transitional state + * as explained at the top of this file if and only if: * - * The atomic acquire/release aware variant of - * mark_rt_mutex_waiters uses a cmpxchg loop. After setting - * the WAITERS bit, the atomic release / acquire can not - * happen anymore and lock->wait_lock protects us from the - * non-atomic case. + * - There is a lock owner. The caller must fixup the + * transient state if it does a trylock or leaves the lock + * function due to a signal or timeout. * - * Note, that this might set lock->owner = - * RT_MUTEX_HAS_WAITERS in the case the lock is not contended - * any more. This is fixed up when we take the ownership. - * This is the transitional state explained at the top of this file. + * - @task acquires the lock and there are no other + * waiters. This is undone in rt_mutex_set_owner(@task) at + * the end of this function. */ mark_rt_mutex_waiters(lock); + /* + * If @lock has an owner, give up. + */ if (rt_mutex_owner(lock)) return 0; /* - * It will get the lock because of one of these conditions: - * 1) there is no waiter - * 2) higher priority than waiters - * 3) it is top waiter + * If @waiter != NULL, @task has already enqueued the waiter + * into @lock waiter list. If @waiter == NULL then this is a + * trylock attempt. */ - if (rt_mutex_has_waiters(lock)) { - if (task->prio >= rt_mutex_top_waiter(lock)->prio) { - if (!waiter || waiter != rt_mutex_top_waiter(lock)) - return 0; - } - } - - if (waiter || rt_mutex_has_waiters(lock)) { - unsigned long flags; - struct rt_mutex_waiter *top; - - raw_spin_lock_irqsave(&task->pi_lock, flags); + if (waiter) { + /* + * If waiter is not the highest priority waiter of + * @lock, give up. + */ + if (waiter != rt_mutex_top_waiter(lock)) + return 0; - /* remove the queued waiter. */ - if (waiter) { - rt_mutex_dequeue(lock, waiter); - task->pi_blocked_on = NULL; - } + /* + * We can acquire the lock. Remove the waiter from the + * lock waiters list. + */ + rt_mutex_dequeue(lock, waiter); + } else { /* - * We have to enqueue the top waiter(if it exists) into - * task->pi_waiters list. + * If the lock has waiters already we check whether @task is + * eligible to take over the lock. + * + * If there are no other waiters, @task can acquire + * the lock. @task->pi_blocked_on is NULL, so it does + * not need to be dequeued. */ if (rt_mutex_has_waiters(lock)) { - top = rt_mutex_top_waiter(lock); - rt_mutex_enqueue_pi(task, top); + /* + * If @task->prio is greater than or equal to + * the top waiter priority (kernel view), + * @task lost. + */ + if (task->prio >= rt_mutex_top_waiter(lock)->prio) + return 0; + + /* + * The current top waiter stays enqueued. We + * don't have to change anything in the lock + * waiters order. + */ + } else { + /* + * No waiters. Take the lock without the + * pi_lock dance.@task->pi_blocked_on is NULL + * and we have no waiters to enqueue in @task + * pi waiters list. + */ + goto takeit; } - raw_spin_unlock_irqrestore(&task->pi_lock, flags); } + /* + * Clear @task->pi_blocked_on. Requires protection by + * @task->pi_lock. Redundant operation for the @waiter == NULL + * case, but conditionals are more expensive than a redundant + * store. + */ + raw_spin_lock_irqsave(&task->pi_lock, flags); + task->pi_blocked_on = NULL; + /* + * Finish the lock acquisition. @task is the new owner. If + * other waiters exist we have to insert the highest priority + * waiter into @task->pi_waiters list. + */ + if (rt_mutex_has_waiters(lock)) + rt_mutex_enqueue_pi(task, rt_mutex_top_waiter(lock)); + raw_spin_unlock_irqrestore(&task->pi_lock, flags); + +takeit: /* We got the lock. */ debug_rt_mutex_lock(lock); + /* + * This either preserves the RT_MUTEX_HAS_WAITERS bit if there + * are still waiters or clears it. + */ rt_mutex_set_owner(lock, task); rt_mutex_deadlock_account_lock(lock, task); @@ -620,7 +873,7 @@ static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task, static int task_blocks_on_rt_mutex(struct rt_mutex *lock, struct rt_mutex_waiter *waiter, struct task_struct *task, - int detect_deadlock) + enum rtmutex_chainwalk chwalk) { struct task_struct *owner = rt_mutex_owner(lock); struct rt_mutex_waiter *top_waiter = waiter; @@ -666,7 +919,7 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock, __rt_mutex_adjust_prio(owner); if (owner->pi_blocked_on) chain_walk = 1; - } else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) { + } else if (rt_mutex_cond_detect_deadlock(waiter, chwalk)) { chain_walk = 1; } @@ -691,7 +944,7 @@ static int task_blocks_on_rt_mutex(struct rt_mutex *lock, raw_spin_unlock(&lock->wait_lock); - res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, + res = rt_mutex_adjust_prio_chain(owner, chwalk, lock, next_lock, waiter, task); raw_spin_lock(&lock->wait_lock); @@ -753,9 +1006,9 @@ static void wakeup_next_waiter(struct rt_mutex *lock) static void remove_waiter(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) { - int first = (waiter == rt_mutex_top_waiter(lock)); + bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock)); struct task_struct *owner = rt_mutex_owner(lock); - struct rt_mutex *next_lock = NULL; + struct rt_mutex *next_lock; unsigned long flags; raw_spin_lock_irqsave(¤t->pi_lock, flags); @@ -763,29 +1016,31 @@ static void remove_waiter(struct rt_mutex *lock, current->pi_blocked_on = NULL; raw_spin_unlock_irqrestore(¤t->pi_lock, flags); - if (!owner) + /* + * Only update priority if the waiter was the highest priority + * waiter of the lock and there is an owner to update. + */ + if (!owner || !is_top_waiter) return; - if (first) { - - raw_spin_lock_irqsave(&owner->pi_lock, flags); + raw_spin_lock_irqsave(&owner->pi_lock, flags); - rt_mutex_dequeue_pi(owner, waiter); + rt_mutex_dequeue_pi(owner, waiter); - if (rt_mutex_has_waiters(lock)) { - struct rt_mutex_waiter *next; + if (rt_mutex_has_waiters(lock)) + rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock)); - next = rt_mutex_top_waiter(lock); - rt_mutex_enqueue_pi(owner, next); - } - __rt_mutex_adjust_prio(owner); + __rt_mutex_adjust_prio(owner); - /* Store the lock on which owner is blocked or NULL */ - next_lock = task_blocked_on_lock(owner); + /* Store the lock on which owner is blocked or NULL */ + next_lock = task_blocked_on_lock(owner); - raw_spin_unlock_irqrestore(&owner->pi_lock, flags); - } + raw_spin_unlock_irqrestore(&owner->pi_lock, flags); + /* + * Don't walk the chain, if the owner task is not blocked + * itself. + */ if (!next_lock) return; @@ -794,7 +1049,8 @@ static void remove_waiter(struct rt_mutex *lock, raw_spin_unlock(&lock->wait_lock); - rt_mutex_adjust_prio_chain(owner, 0, lock, next_lock, NULL, current); + rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock, + next_lock, NULL, current); raw_spin_lock(&lock->wait_lock); } @@ -824,7 +1080,8 @@ void rt_mutex_adjust_pi(struct task_struct *task) /* gets dropped in rt_mutex_adjust_prio_chain()! */ get_task_struct(task); - rt_mutex_adjust_prio_chain(task, 0, NULL, next_lock, NULL, task); + rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL, + next_lock, NULL, task); } /** @@ -902,7 +1159,7 @@ static void rt_mutex_handle_deadlock(int res, int detect_deadlock, static int __sched rt_mutex_slowlock(struct rt_mutex *lock, int state, struct hrtimer_sleeper *timeout, - int detect_deadlock) + enum rtmutex_chainwalk chwalk) { struct rt_mutex_waiter waiter; int ret = 0; @@ -928,7 +1185,7 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, timeout->task = NULL; } - ret = task_blocks_on_rt_mutex(lock, &waiter, current, detect_deadlock); + ret = task_blocks_on_rt_mutex(lock, &waiter, current, chwalk); if (likely(!ret)) ret = __rt_mutex_slowlock(lock, state, timeout, &waiter); @@ -937,7 +1194,7 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, if (unlikely(ret)) { remove_waiter(lock, &waiter); - rt_mutex_handle_deadlock(ret, detect_deadlock, &waiter); + rt_mutex_handle_deadlock(ret, chwalk, &waiter); } /* @@ -960,22 +1217,31 @@ rt_mutex_slowlock(struct rt_mutex *lock, int state, /* * Slow path try-lock function: */ -static inline int -rt_mutex_slowtrylock(struct rt_mutex *lock) +static inline int rt_mutex_slowtrylock(struct rt_mutex *lock) { - int ret = 0; + int ret; + + /* + * If the lock already has an owner we fail to get the lock. + * This can be done without taking the @lock->wait_lock as + * it is only being read, and this is a trylock anyway. + */ + if (rt_mutex_owner(lock)) + return 0; + /* + * The mutex has currently no owner. Lock the wait lock and + * try to acquire the lock. + */ raw_spin_lock(&lock->wait_lock); - if (likely(rt_mutex_owner(lock) != current)) { + ret = try_to_take_rt_mutex(lock, current, NULL); - ret = try_to_take_rt_mutex(lock, current, NULL); - /* - * try_to_take_rt_mutex() sets the lock waiters - * bit unconditionally. Clean this up. - */ - fixup_rt_mutex_waiters(lock); - } + /* + * try_to_take_rt_mutex() sets the lock waiters bit + * unconditionally. Clean this up. + */ + fixup_rt_mutex_waiters(lock); raw_spin_unlock(&lock->wait_lock); @@ -1053,30 +1319,31 @@ rt_mutex_slowunlock(struct rt_mutex *lock) */ static inline int rt_mutex_fastlock(struct rt_mutex *lock, int state, - int detect_deadlock, int (*slowfn)(struct rt_mutex *lock, int state, struct hrtimer_sleeper *timeout, - int detect_deadlock)) + enum rtmutex_chainwalk chwalk)) { - if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { + if (likely(rt_mutex_cmpxchg(lock, NULL, current))) { rt_mutex_deadlock_account_lock(lock, current); return 0; } else - return slowfn(lock, state, NULL, detect_deadlock); + return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK); } static inline int rt_mutex_timed_fastlock(struct rt_mutex *lock, int state, - struct hrtimer_sleeper *timeout, int detect_deadlock, + struct hrtimer_sleeper *timeout, + enum rtmutex_chainwalk chwalk, int (*slowfn)(struct rt_mutex *lock, int state, struct hrtimer_sleeper *timeout, - int detect_deadlock)) + enum rtmutex_chainwalk chwalk)) { - if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { + if (chwalk == RT_MUTEX_MIN_CHAINWALK && + likely(rt_mutex_cmpxchg(lock, NULL, current))) { rt_mutex_deadlock_account_lock(lock, current); return 0; } else - return slowfn(lock, state, timeout, detect_deadlock); + return slowfn(lock, state, timeout, chwalk); } static inline int @@ -1109,54 +1376,61 @@ void __sched rt_mutex_lock(struct rt_mutex *lock) { might_sleep(); - rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock); + rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, rt_mutex_slowlock); } EXPORT_SYMBOL_GPL(rt_mutex_lock); /** * rt_mutex_lock_interruptible - lock a rt_mutex interruptible * - * @lock: the rt_mutex to be locked - * @detect_deadlock: deadlock detection on/off + * @lock: the rt_mutex to be locked * * Returns: - * 0 on success - * -EINTR when interrupted by a signal - * -EDEADLK when the lock would deadlock (when deadlock detection is on) + * 0 on success + * -EINTR when interrupted by a signal */ -int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock, - int detect_deadlock) +int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock) { might_sleep(); - return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, - detect_deadlock, rt_mutex_slowlock); + return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, rt_mutex_slowlock); } EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible); +/* + * Futex variant with full deadlock detection. + */ +int rt_mutex_timed_futex_lock(struct rt_mutex *lock, + struct hrtimer_sleeper *timeout) +{ + might_sleep(); + + return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, + RT_MUTEX_FULL_CHAINWALK, + rt_mutex_slowlock); +} + /** * rt_mutex_timed_lock - lock a rt_mutex interruptible * the timeout structure is provided * by the caller * - * @lock: the rt_mutex to be locked + * @lock: the rt_mutex to be locked * @timeout: timeout structure or NULL (no timeout) - * @detect_deadlock: deadlock detection on/off * * Returns: - * 0 on success - * -EINTR when interrupted by a signal + * 0 on success + * -EINTR when interrupted by a signal * -ETIMEDOUT when the timeout expired - * -EDEADLK when the lock would deadlock (when deadlock detection is on) */ int -rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout, - int detect_deadlock) +rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout) { might_sleep(); return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, - detect_deadlock, rt_mutex_slowlock); + RT_MUTEX_MIN_CHAINWALK, + rt_mutex_slowlock); } EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); @@ -1262,7 +1536,6 @@ void rt_mutex_proxy_unlock(struct rt_mutex *lock, * @lock: the rt_mutex to take * @waiter: the pre-initialized rt_mutex_waiter * @task: the task to prepare - * @detect_deadlock: perform deadlock detection (1) or not (0) * * Returns: * 0 - task blocked on lock @@ -1273,7 +1546,7 @@ void rt_mutex_proxy_unlock(struct rt_mutex *lock, */ int rt_mutex_start_proxy_lock(struct rt_mutex *lock, struct rt_mutex_waiter *waiter, - struct task_struct *task, int detect_deadlock) + struct task_struct *task) { int ret; @@ -1285,7 +1558,8 @@ int rt_mutex_start_proxy_lock(struct rt_mutex *lock, } /* We enforce deadlock detection for futexes */ - ret = task_blocks_on_rt_mutex(lock, waiter, task, 1); + ret = task_blocks_on_rt_mutex(lock, waiter, task, + RT_MUTEX_FULL_CHAINWALK); if (ret && !rt_mutex_owner(lock)) { /* @@ -1331,22 +1605,20 @@ struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock) * rt_mutex_finish_proxy_lock() - Complete lock acquisition * @lock: the rt_mutex we were woken on * @to: the timeout, null if none. hrtimer should already have - * been started. + * been started. * @waiter: the pre-initialized rt_mutex_waiter - * @detect_deadlock: perform deadlock detection (1) or not (0) * * Complete the lock acquisition started our behalf by another thread. * * Returns: * 0 - success - * <0 - error, one of -EINTR, -ETIMEDOUT, or -EDEADLK + * <0 - error, one of -EINTR, -ETIMEDOUT * * Special API call for PI-futex requeue support */ int rt_mutex_finish_proxy_lock(struct rt_mutex *lock, struct hrtimer_sleeper *to, - struct rt_mutex_waiter *waiter, - int detect_deadlock) + struct rt_mutex_waiter *waiter) { int ret; diff --git a/kernel/locking/rtmutex.h b/kernel/locking/rtmutex.h index f6a1f3c..c406058 100644 --- a/kernel/locking/rtmutex.h +++ b/kernel/locking/rtmutex.h @@ -22,10 +22,15 @@ #define debug_rt_mutex_init(m, n) do { } while (0) #define debug_rt_mutex_deadlock(d, a ,l) do { } while (0) #define debug_rt_mutex_print_deadlock(w) do { } while (0) -#define debug_rt_mutex_detect_deadlock(w,d) (d) #define debug_rt_mutex_reset_waiter(w) do { } while (0) static inline void rt_mutex_print_deadlock(struct rt_mutex_waiter *w) { WARN(1, "rtmutex deadlock detected\n"); } + +static inline bool debug_rt_mutex_detect_deadlock(struct rt_mutex_waiter *w, + enum rtmutex_chainwalk walk) +{ + return walk == RT_MUTEX_FULL_CHAINWALK; +} diff --git a/kernel/locking/rtmutex_common.h b/kernel/locking/rtmutex_common.h index 7431a9c..8552125 100644 --- a/kernel/locking/rtmutex_common.h +++ b/kernel/locking/rtmutex_common.h @@ -102,6 +102,21 @@ static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock) } /* + * Constants for rt mutex functions which have a selectable deadlock + * detection. + * + * RT_MUTEX_MIN_CHAINWALK: Stops the lock chain walk when there are + * no further PI adjustments to be made. + * + * RT_MUTEX_FULL_CHAINWALK: Invoke deadlock detection with a full + * walk of the lock chain. + */ +enum rtmutex_chainwalk { + RT_MUTEX_MIN_CHAINWALK, + RT_MUTEX_FULL_CHAINWALK, +}; + +/* * PI-futex support (proxy locking functions, etc.): */ extern struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock); @@ -111,12 +126,11 @@ extern void rt_mutex_proxy_unlock(struct rt_mutex *lock, struct task_struct *proxy_owner); extern int rt_mutex_start_proxy_lock(struct rt_mutex *lock, struct rt_mutex_waiter *waiter, - struct task_struct *task, - int detect_deadlock); + struct task_struct *task); extern int rt_mutex_finish_proxy_lock(struct rt_mutex *lock, struct hrtimer_sleeper *to, - struct rt_mutex_waiter *waiter, - int detect_deadlock); + struct rt_mutex_waiter *waiter); +extern int rt_mutex_timed_futex_lock(struct rt_mutex *l, struct hrtimer_sleeper *to); #ifdef CONFIG_DEBUG_RT_MUTEXES # include "rtmutex-debug.h" diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index a2391ac..d6203fa 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -329,7 +329,7 @@ bool rwsem_spin_on_owner(struct rw_semaphore *sem, struct task_struct *owner) if (need_resched()) break; - arch_mutex_cpu_relax(); + cpu_relax_lowlatency(); } rcu_read_unlock(); @@ -381,7 +381,7 @@ static bool rwsem_optimistic_spin(struct rw_semaphore *sem) * memory barriers as we'll eventually observe the right * values at the cost of a few extra spins. */ - arch_mutex_cpu_relax(); + cpu_relax_lowlatency(); } osq_unlock(&sem->osq); done: diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 12132e4..901096d 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -835,7 +835,7 @@ config DEBUG_RT_MUTEXES config RT_MUTEX_TESTER bool "Built-in scriptable tester for rt-mutexes" - depends on DEBUG_KERNEL && RT_MUTEXES + depends on DEBUG_KERNEL && RT_MUTEXES && BROKEN help This option enables a rt-mutex tester. diff --git a/lib/lockref.c b/lib/lockref.c index f07a40d..d2233de 100644 --- a/lib/lockref.c +++ b/lib/lockref.c @@ -1,6 +1,5 @@ #include <linux/export.h> #include <linux/lockref.h> -#include <linux/mutex.h> #if USE_CMPXCHG_LOCKREF @@ -29,7 +28,7 @@ if (likely(old.lock_count == prev.lock_count)) { \ SUCCESS; \ } \ - arch_mutex_cpu_relax(); \ + cpu_relax_lowlatency(); \ } \ } while (0) |
