diff options
| -rw-r--r-- | fs/exec.c | 4 | ||||
| -rw-r--r-- | include/linux/sched.h | 32 | ||||
| -rw-r--r-- | kernel/exit.c | 1 | ||||
| -rw-r--r-- | kernel/fork.c | 10 | ||||
| -rw-r--r-- | kernel/pid.c | 22 | ||||
| -rw-r--r-- | kernel/rcupdate.c | 1 | ||||
| -rw-r--r-- | kernel/sched.c | 7 | ||||
| -rw-r--r-- | kernel/signal.c | 97 |
8 files changed, 143 insertions, 31 deletions
@@ -760,7 +760,7 @@ no_thread_group: spin_lock(&oldsighand->siglock); spin_lock(&newsighand->siglock); - current->sighand = newsighand; + rcu_assign_pointer(current->sighand, newsighand); recalc_sigpending(); spin_unlock(&newsighand->siglock); @@ -768,7 +768,7 @@ no_thread_group: write_unlock_irq(&tasklist_lock); if (atomic_dec_and_test(&oldsighand->count)) - kmem_cache_free(sighand_cachep, oldsighand); + sighand_free(oldsighand); } BUG_ON(!thread_group_leader(current)); diff --git a/include/linux/sched.h b/include/linux/sched.h index a746620..a6af77e 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -34,6 +34,7 @@ #include <linux/percpu.h> #include <linux/topology.h> #include <linux/seccomp.h> +#include <linux/rcupdate.h> #include <linux/auxvec.h> /* For AT_VECTOR_SIZE */ @@ -350,8 +351,16 @@ struct sighand_struct { atomic_t count; struct k_sigaction action[_NSIG]; spinlock_t siglock; + struct rcu_head rcu; }; +extern void sighand_free_cb(struct rcu_head *rhp); + +static inline void sighand_free(struct sighand_struct *sp) +{ + call_rcu(&sp->rcu, sighand_free_cb); +} + /* * NOTE! "signal_struct" does not have it's own * locking, because a shared signal_struct always @@ -844,6 +853,7 @@ struct task_struct { int cpuset_mems_generation; #endif atomic_t fs_excl; /* holding fs exclusive resources */ + struct rcu_head rcu; }; static inline pid_t process_group(struct task_struct *tsk) @@ -867,8 +877,26 @@ static inline int pid_alive(struct task_struct *p) extern void free_task(struct task_struct *tsk); extern void __put_task_struct(struct task_struct *tsk); #define get_task_struct(tsk) do { atomic_inc(&(tsk)->usage); } while(0) -#define put_task_struct(tsk) \ -do { if (atomic_dec_and_test(&(tsk)->usage)) __put_task_struct(tsk); } while(0) + +static inline int get_task_struct_rcu(struct task_struct *t) +{ + int oldusage; + + do { + oldusage = atomic_read(&t->usage); + if (oldusage == 0) + return 0; + } while (cmpxchg(&t->usage.counter, oldusage, oldusage+1) != oldusage); + return 1; +} + +extern void __put_task_struct_cb(struct rcu_head *rhp); + +static inline void put_task_struct(struct task_struct *t) +{ + if (atomic_dec_and_test(&t->usage)) + call_rcu(&t->rcu, __put_task_struct_cb); +} /* * Per process flags diff --git a/kernel/exit.c b/kernel/exit.c index ee51568..c73a7eb 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -72,7 +72,6 @@ repeat: __ptrace_unlink(p); BUG_ON(!list_empty(&p->ptrace_list) || !list_empty(&p->ptrace_children)); __exit_signal(p); - __exit_sighand(p); /* * Note that the fastpath in sys_times depends on __exit_signal having * updated the counters before a task is removed from the tasklist of diff --git a/kernel/fork.c b/kernel/fork.c index fb8572a..7fe3adf 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -743,6 +743,14 @@ int unshare_files(void) EXPORT_SYMBOL(unshare_files); +void sighand_free_cb(struct rcu_head *rhp) +{ + struct sighand_struct *sp; + + sp = container_of(rhp, struct sighand_struct, rcu); + kmem_cache_free(sighand_cachep, sp); +} + static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk) { struct sighand_struct *sig; @@ -752,7 +760,7 @@ static inline int copy_sighand(unsigned long clone_flags, struct task_struct * t return 0; } sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); - tsk->sighand = sig; + rcu_assign_pointer(tsk->sighand, sig); if (!sig) return -ENOMEM; spin_lock_init(&sig->siglock); diff --git a/kernel/pid.c b/kernel/pid.c index edba31c..1acc072 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -136,7 +136,7 @@ struct pid * fastcall find_pid(enum pid_type type, int nr) struct hlist_node *elem; struct pid *pid; - hlist_for_each_entry(pid, elem, + hlist_for_each_entry_rcu(pid, elem, &pid_hash[type][pid_hashfn(nr)], pid_chain) { if (pid->nr == nr) return pid; @@ -150,15 +150,15 @@ int fastcall attach_pid(task_t *task, enum pid_type type, int nr) task_pid = &task->pids[type]; pid = find_pid(type, nr); + task_pid->nr = nr; if (pid == NULL) { - hlist_add_head(&task_pid->pid_chain, - &pid_hash[type][pid_hashfn(nr)]); INIT_LIST_HEAD(&task_pid->pid_list); + hlist_add_head_rcu(&task_pid->pid_chain, + &pid_hash[type][pid_hashfn(nr)]); } else { INIT_HLIST_NODE(&task_pid->pid_chain); - list_add_tail(&task_pid->pid_list, &pid->pid_list); + list_add_tail_rcu(&task_pid->pid_list, &pid->pid_list); } - task_pid->nr = nr; return 0; } @@ -170,20 +170,20 @@ static fastcall int __detach_pid(task_t *task, enum pid_type type) pid = &task->pids[type]; if (!hlist_unhashed(&pid->pid_chain)) { - hlist_del(&pid->pid_chain); - if (list_empty(&pid->pid_list)) + if (list_empty(&pid->pid_list)) { nr = pid->nr; - else { + hlist_del_rcu(&pid->pid_chain); + } else { pid_next = list_entry(pid->pid_list.next, struct pid, pid_list); /* insert next pid from pid_list to hash */ - hlist_add_head(&pid_next->pid_chain, - &pid_hash[type][pid_hashfn(pid_next->nr)]); + hlist_replace_rcu(&pid->pid_chain, + &pid_next->pid_chain); } } - list_del(&pid->pid_list); + list_del_rcu(&pid->pid_list); pid->nr = 0; return nr; diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index c9afc61..0a669bd 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -35,6 +35,7 @@ #include <linux/init.h> #include <linux/spinlock.h> #include <linux/smp.h> +#include <linux/rcupdate.h> #include <linux/interrupt.h> #include <linux/sched.h> #include <asm/atomic.h> diff --git a/kernel/sched.c b/kernel/sched.c index 6f46c94..9273309 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -176,6 +176,13 @@ static unsigned int task_timeslice(task_t *p) #define task_hot(p, now, sd) ((long long) ((now) - (p)->last_ran) \ < (long long) (sd)->cache_hot_time) +void __put_task_struct_cb(struct rcu_head *rhp) +{ + __put_task_struct(container_of(rhp, struct task_struct, rcu)); +} + +EXPORT_SYMBOL_GPL(__put_task_struct_cb); + /* * These are the runqueue data structures: */ diff --git a/kernel/signal.c b/kernel/signal.c index d7611f1..64737c7 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -329,13 +329,20 @@ void __exit_sighand(struct task_struct *tsk) /* Ok, we're done with the signal handlers */ tsk->sighand = NULL; if (atomic_dec_and_test(&sighand->count)) - kmem_cache_free(sighand_cachep, sighand); + sighand_free(sighand); } void exit_sighand(struct task_struct *tsk) { write_lock_irq(&tasklist_lock); - __exit_sighand(tsk); + rcu_read_lock(); + if (tsk->sighand != NULL) { + struct sighand_struct *sighand = rcu_dereference(tsk->sighand); + spin_lock(&sighand->siglock); + __exit_sighand(tsk); + spin_unlock(&sighand->siglock); + } + rcu_read_unlock(); write_unlock_irq(&tasklist_lock); } @@ -345,12 +352,14 @@ void exit_sighand(struct task_struct *tsk) void __exit_signal(struct task_struct *tsk) { struct signal_struct * sig = tsk->signal; - struct sighand_struct * sighand = tsk->sighand; + struct sighand_struct * sighand; if (!sig) BUG(); if (!atomic_read(&sig->count)) BUG(); + rcu_read_lock(); + sighand = rcu_dereference(tsk->sighand); spin_lock(&sighand->siglock); posix_cpu_timers_exit(tsk); if (atomic_dec_and_test(&sig->count)) { @@ -358,6 +367,7 @@ void __exit_signal(struct task_struct *tsk) if (tsk == sig->curr_target) sig->curr_target = next_thread(tsk); tsk->signal = NULL; + __exit_sighand(tsk); spin_unlock(&sighand->siglock); flush_sigqueue(&sig->shared_pending); } else { @@ -389,9 +399,11 @@ void __exit_signal(struct task_struct *tsk) sig->nvcsw += tsk->nvcsw; sig->nivcsw += tsk->nivcsw; sig->sched_time += tsk->sched_time; + __exit_sighand(tsk); spin_unlock(&sighand->siglock); sig = NULL; /* Marker for below. */ } + rcu_read_unlock(); clear_tsk_thread_flag(tsk,TIF_SIGPENDING); flush_sigqueue(&tsk->pending); if (sig) { @@ -1080,18 +1092,28 @@ void zap_other_threads(struct task_struct *p) } /* - * Must be called with the tasklist_lock held for reading! + * Must be called under rcu_read_lock() or with tasklist_lock read-held. */ int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p) { unsigned long flags; + struct sighand_struct *sp; int ret; +retry: ret = check_kill_permission(sig, info, p); - if (!ret && sig && p->sighand) { - spin_lock_irqsave(&p->sighand->siglock, flags); + if (!ret && sig && (sp = p->sighand)) { + if (!get_task_struct_rcu(p)) + return -ESRCH; + spin_lock_irqsave(&sp->siglock, flags); + if (p->sighand != sp) { + spin_unlock_irqrestore(&sp->siglock, flags); + put_task_struct(p); + goto retry; + } ret = __group_send_sig_info(sig, info, p); - spin_unlock_irqrestore(&p->sighand->siglock, flags); + spin_unlock_irqrestore(&sp->siglock, flags); + put_task_struct(p); } return ret; @@ -1136,14 +1158,21 @@ int kill_proc_info(int sig, struct siginfo *info, pid_t pid) { int error; + int acquired_tasklist_lock = 0; struct task_struct *p; - read_lock(&tasklist_lock); + rcu_read_lock(); + if (unlikely(sig_kernel_stop(sig) || sig == SIGCONT)) { + read_lock(&tasklist_lock); + acquired_tasklist_lock = 1; + } p = find_task_by_pid(pid); error = -ESRCH; if (p) error = group_send_sig_info(sig, info, p); - read_unlock(&tasklist_lock); + if (unlikely(acquired_tasklist_lock)) + read_unlock(&tasklist_lock); + rcu_read_unlock(); return error; } @@ -1355,16 +1384,54 @@ send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p) { unsigned long flags; int ret = 0; + struct sighand_struct *sh; BUG_ON(!(q->flags & SIGQUEUE_PREALLOC)); - read_lock(&tasklist_lock); + + /* + * The rcu based delayed sighand destroy makes it possible to + * run this without tasklist lock held. The task struct itself + * cannot go away as create_timer did get_task_struct(). + * + * We return -1, when the task is marked exiting, so + * posix_timer_event can redirect it to the group leader + */ + rcu_read_lock(); if (unlikely(p->flags & PF_EXITING)) { ret = -1; goto out_err; } - spin_lock_irqsave(&p->sighand->siglock, flags); +retry: + sh = rcu_dereference(p->sighand); + + spin_lock_irqsave(&sh->siglock, flags); + if (p->sighand != sh) { + /* We raced with exec() in a multithreaded process... */ + spin_unlock_irqrestore(&sh->siglock, flags); + goto retry; + } + + /* + * We do the check here again to handle the following scenario: + * + * CPU 0 CPU 1 + * send_sigqueue + * check PF_EXITING + * interrupt exit code running + * __exit_signal + * lock sighand->siglock + * unlock sighand->siglock + * lock sh->siglock + * add(tsk->pending) flush_sigqueue(tsk->pending) + * + */ + + if (unlikely(p->flags & PF_EXITING)) { + ret = -1; + goto out; + } if (unlikely(!list_empty(&q->list))) { /* @@ -1388,9 +1455,9 @@ send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p) signal_wake_up(p, sig == SIGKILL); out: - spin_unlock_irqrestore(&p->sighand->siglock, flags); + spin_unlock_irqrestore(&sh->siglock, flags); out_err: - read_unlock(&tasklist_lock); + rcu_read_unlock(); return ret; } @@ -1402,7 +1469,9 @@ send_group_sigqueue(int sig, struct sigqueue *q, struct task_struct *p) int ret = 0; BUG_ON(!(q->flags & SIGQUEUE_PREALLOC)); + read_lock(&tasklist_lock); + /* Since it_lock is held, p->sighand cannot be NULL. */ spin_lock_irqsave(&p->sighand->siglock, flags); handle_stop_signal(sig, p); @@ -1436,7 +1505,7 @@ send_group_sigqueue(int sig, struct sigqueue *q, struct task_struct *p) out: spin_unlock_irqrestore(&p->sighand->siglock, flags); read_unlock(&tasklist_lock); - return(ret); + return ret; } /* |
