From 7974891db234467eaf1fec613ec0129cb4ac2332 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 28 Jun 2010 14:15:54 +0200 Subject: x86: Always use irq stacks IRQ stacks provide much better safety against unexpected stack use from interrupts, at the minimal downside of slightly higher memory usage. Enable irq stacks also for the default 8k stack on 32-bit kernels to minimize the problem of stack overflows through interrupt activity. This is what the 64-bit kernel and various other architectures already do. Signed-off-by: Christoph Hellwig LKML-Reference: <20100628121554.GA6605@lst.de> Signed-off-by: Thomas Gleixner --- Documentation/x86/x86_64/kernel-stacks | 6 +++--- arch/x86/Kconfig.debug | 3 +-- arch/x86/include/asm/irq.h | 12 +++++------- arch/x86/kernel/irq_32.c | 6 ------ 4 files changed, 9 insertions(+), 18 deletions(-) diff --git a/Documentation/x86/x86_64/kernel-stacks b/Documentation/x86/x86_64/kernel-stacks index 5ad65d5..a01eec5 100644 --- a/Documentation/x86/x86_64/kernel-stacks +++ b/Documentation/x86/x86_64/kernel-stacks @@ -18,9 +18,9 @@ specialized stacks contain no useful data. The main CPU stacks are: Used for external hardware interrupts. If this is the first external hardware interrupt (i.e. not a nested hardware interrupt) then the kernel switches from the current task to the interrupt stack. Like - the split thread and interrupt stacks on i386 (with CONFIG_4KSTACKS), - this gives more room for kernel interrupt processing without having - to increase the size of every per thread stack. + the split thread and interrupt stacks on i386, this gives more room + for kernel interrupt processing without having to increase the size + of every per thread stack. The interrupt stack is also used when processing a softirq. diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index 7508508..badda8e 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -128,8 +128,7 @@ config 4KSTACKS If you say Y here the kernel will use a 4Kb stacksize for the kernel stack attached to each process/thread. This facilitates running more threads on a system and also reduces the pressure - on the VM subsystem for higher order allocations. This option - will also use IRQ stacks to compensate for the reduced stackspace. + on the VM subsystem for higher order allocations. config DOUBLEFAULT default y diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h index 5458380..0bf5b00 100644 --- a/arch/x86/include/asm/irq.h +++ b/arch/x86/include/asm/irq.h @@ -19,18 +19,16 @@ static inline int irq_canonicalize(int irq) # define ARCH_HAS_NMI_WATCHDOG #endif -#ifdef CONFIG_4KSTACKS - extern void irq_ctx_init(int cpu); - extern void irq_ctx_exit(int cpu); -# define __ARCH_HAS_DO_SOFTIRQ +#ifdef CONFIG_X86_32 +extern void irq_ctx_init(int cpu); +extern void irq_ctx_exit(int cpu); #else # define irq_ctx_init(cpu) do { } while (0) # define irq_ctx_exit(cpu) do { } while (0) -# ifdef CONFIG_X86_64 -# define __ARCH_HAS_DO_SOFTIRQ -# endif #endif +#define __ARCH_HAS_DO_SOFTIRQ + #ifdef CONFIG_HOTPLUG_CPU #include extern void fixup_irqs(void); diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c index 10709f2..67f5f9f 100644 --- a/arch/x86/kernel/irq_32.c +++ b/arch/x86/kernel/irq_32.c @@ -49,7 +49,6 @@ static inline int check_stack_overflow(void) { return 0; } static inline void print_stack_overflow(void) { } #endif -#ifdef CONFIG_4KSTACKS /* * per-CPU IRQ handling contexts (thread information and stack) */ @@ -187,11 +186,6 @@ asmlinkage void do_softirq(void) local_irq_restore(flags); } -#else -static inline int -execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq) { return 0; } -#endif - bool handle_irq(unsigned irq, struct pt_regs *regs) { struct irq_desc *desc; -- cgit v1.1 From dcfa726280116dd31adad37da940f542663567d0 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 28 Jun 2010 14:16:14 +0200 Subject: x86: Remove CONFIG_4KSTACKS These days 4 kilobytes of stack just aren't enough for reliably operation, and people using lots of threads have long switched to 64-bit kernels, so remove the CONFIG_4KSTACKS option. Signed-off-by: Christoph Hellwig LKML-Reference: <20100628121614.GB6605@lst.de> Signed-off-by: Thomas Gleixner --- arch/x86/Kconfig.debug | 9 --------- arch/x86/include/asm/module.h | 7 +------ arch/x86/include/asm/page_32_types.h | 4 ---- 3 files changed, 1 insertion(+), 19 deletions(-) diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index badda8e..7f15308 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -121,15 +121,6 @@ config DEBUG_NX_TEST and the software setup of this feature. If in doubt, say "N" -config 4KSTACKS - bool "Use 4Kb for kernel stacks instead of 8Kb" - depends on X86_32 - ---help--- - If you say Y here the kernel will use a 4Kb stacksize for the - kernel stack attached to each process/thread. This facilitates - running more threads on a system and also reduces the pressure - on the VM subsystem for higher order allocations. - config DOUBLEFAULT default y bool "Enable doublefault exception handler" if EMBEDDED diff --git a/arch/x86/include/asm/module.h b/arch/x86/include/asm/module.h index 3e2ce58..67763c5 100644 --- a/arch/x86/include/asm/module.h +++ b/arch/x86/include/asm/module.h @@ -60,12 +60,7 @@ #endif #ifdef CONFIG_X86_32 -# ifdef CONFIG_4KSTACKS -# define MODULE_STACKSIZE "4KSTACKS " -# else -# define MODULE_STACKSIZE "" -# endif -# define MODULE_ARCH_VERMAGIC MODULE_PROC_FAMILY MODULE_STACKSIZE +# define MODULE_ARCH_VERMAGIC MODULE_PROC_FAMILY #endif #endif /* _ASM_X86_MODULE_H */ diff --git a/arch/x86/include/asm/page_32_types.h b/arch/x86/include/asm/page_32_types.h index 6f1b733..ade619f 100644 --- a/arch/x86/include/asm/page_32_types.h +++ b/arch/x86/include/asm/page_32_types.h @@ -15,11 +15,7 @@ */ #define __PAGE_OFFSET _AC(CONFIG_PAGE_OFFSET, UL) -#ifdef CONFIG_4KSTACKS -#define THREAD_ORDER 0 -#else #define THREAD_ORDER 1 -#endif #define THREAD_SIZE (PAGE_SIZE << THREAD_ORDER) #define STACKFAULT_STACK 0 -- cgit v1.1 From 25897374297906eeebef8864299406bdcb5859c3 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 27 Jul 2010 14:13:13 +0200 Subject: x86-32: Align IRQ stacks properly As suggested by Steven Rostedt we need to align the IRQ stacks to the stack size, not just the page size to make them work for stack traces and other things that depend on finding the stack slot itself with 8k stacks. Signed-off-by: Christoph Hellwig LKML-Reference: <20100727121313.GA19976@lst.de> Signed-off-by: H. Peter Anvin --- arch/x86/kernel/irq_32.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c index 67f5f9f..3b5609f 100644 --- a/arch/x86/kernel/irq_32.c +++ b/arch/x86/kernel/irq_32.c @@ -55,7 +55,7 @@ static inline void print_stack_overflow(void) { } union irq_ctx { struct thread_info tinfo; u32 stack[THREAD_SIZE/sizeof(u32)]; -} __attribute__((aligned(PAGE_SIZE))); +} __attribute__((aligned(THREAD_SIZE))); static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx); static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx); -- cgit v1.1 From 1813a68457bb45b378d5bbec615b167deff3bcfc Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Tue, 20 Jul 2010 15:22:54 -0700 Subject: x86: Move alloc_desk_mask variables inside ifdef They are only useful with CONFIG_CPUMASK_OFFSTACK Avoids hundreds of warnings with a gcc 4.6 -Wall build. Signed-off-by: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Thomas Gleixner --- include/linux/irq.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/irq.h b/include/linux/irq.h index c03243a..fff1d77 100644 --- a/include/linux/irq.h +++ b/include/linux/irq.h @@ -439,12 +439,12 @@ extern int set_irq_msi(unsigned int irq, struct msi_desc *entry); static inline bool alloc_desc_masks(struct irq_desc *desc, int node, bool boot) { +#ifdef CONFIG_CPUMASK_OFFSTACK gfp_t gfp = GFP_ATOMIC; if (boot) gfp = GFP_NOWAIT; -#ifdef CONFIG_CPUMASK_OFFSTACK if (!alloc_cpumask_var_node(&desc->affinity, gfp, node)) return false; -- cgit v1.1 From fe8e0c25cad28e8858ecfa5863333c70685a6811 Mon Sep 17 00:00:00 2001 From: Alexander van Heukelum Date: Mon, 6 Sep 2010 20:53:42 +0200 Subject: x86, 32-bit: Align percpu area and irq stacks to THREAD_SIZE The irq stacks, located in the percpu-area, need to be THREAD_SIZE aligned. Add the infrastucture to align percpu variables to larger-than-pagesize amounts within the percpu area, and use it to specify the alignment for the irq stacks. Also align the percpu area itself to THREAD_SIZE. This should make irq stacks work with 8K THREAD_SIZE. Signed-off-by: Alexander van Heukelum Cc: Tejun Heo Cc: hch@lst.de LKML-Reference: <1283799222.15941.1393621887@webmail.messagingengine.com> Signed-off-by: Ingo Molnar --- arch/x86/kernel/irq_32.c | 4 ++-- arch/x86/kernel/vmlinux.lds.S | 2 +- include/linux/percpu-defs.h | 12 ++++++++++++ 3 files changed, 15 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c index 3b5609f..50fbbe6 100644 --- a/arch/x86/kernel/irq_32.c +++ b/arch/x86/kernel/irq_32.c @@ -60,8 +60,8 @@ union irq_ctx { static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx); static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx); -static DEFINE_PER_CPU_PAGE_ALIGNED(union irq_ctx, hardirq_stack); -static DEFINE_PER_CPU_PAGE_ALIGNED(union irq_ctx, softirq_stack); +static DEFINE_PER_CPU_MULTIPAGE_ALIGNED(union irq_ctx, hardirq_stack, THREAD_SIZE); +static DEFINE_PER_CPU_MULTIPAGE_ALIGNED(union irq_ctx, softirq_stack, THREAD_SIZE); static void call_on_stack(void *func, void *stack) { diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index d0bb522..bb89947 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -273,7 +273,7 @@ SECTIONS } #if !defined(CONFIG_X86_64) || !defined(CONFIG_SMP) - PERCPU(PAGE_SIZE) + PERCPU(THREAD_SIZE) #endif . = ALIGN(PAGE_SIZE); diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h index ce2dc65..ab20d11 100644 --- a/include/linux/percpu-defs.h +++ b/include/linux/percpu-defs.h @@ -139,6 +139,18 @@ __aligned(PAGE_SIZE) /* + * Declaration/definition used for large per-CPU variables that must be + * aligned to something larger than the pagesize. + */ +#define DECLARE_PER_CPU_MULTIPAGE_ALIGNED(type, name, size) \ + DECLARE_PER_CPU_SECTION(type, name, "..page_aligned") \ + __aligned(size) + +#define DEFINE_PER_CPU_MULTIPAGE_ALIGNED(type, name, size) \ + DEFINE_PER_CPU_SECTION(type, name, "..page_aligned") \ + __aligned(size) + +/* * Intermodule exports for per-CPU variables. sparse forgets about * address space across EXPORT_SYMBOL(), change EXPORT_SYMBOL() to * noop if __CHECKER__. -- cgit v1.1