From e211cb68dd3c951b104ff0b47dbaed2c8b8d2399 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Wed, 15 Jul 2015 12:52:04 +0300 Subject: [PATCH] sched/preempt: Fix cond_resched_lock() and cond_resched_softirq() commit fe32d3cd5e8eb0f82e459763374aa80797023403 upstream. These functions check should_resched() before unlocking spinlock/bh-enable: preempt_count always non-zero => should_resched() always returns false. cond_resched_lock() worked iff spin_needbreak is set. This patch adds argument "preempt_offset" to should_resched(). preempt_count offset constants for that: PREEMPT_DISABLE_OFFSET - offset after preempt_disable() PREEMPT_LOCK_OFFSET - offset after spin_lock() SOFTIRQ_DISABLE_OFFSET - offset after local_bh_distable() SOFTIRQ_LOCK_OFFSET - offset after spin_lock_bh() Signed-off-by: Konstantin Khlebnikov Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Graf Cc: Boris Ostrovsky Cc: David Vrabel Cc: Linus Torvalds Cc: Mike Galbraith Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: bdb438065890 ("sched: Extract the basic add/sub preempt_count modifiers") Link: http://lkml.kernel.org/r/20150715095204.12246.98268.stgit@buzz Signed-off-by: Ingo Molnar Signed-off-by: Mike Galbraith Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/preempt.h | 4 ++-- include/asm-generic/preempt.h | 5 +++-- include/linux/preempt.h | 5 +++-- include/linux/preempt_mask.h | 14 +++++++++++--- include/linux/sched.h | 6 ------ kernel/sched/core.c | 6 +++--- 6 files changed, 22 insertions(+), 18 deletions(-) diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h index b39e194f6c8d1..999b4a3e65f58 100644 --- a/arch/x86/include/asm/preempt.h +++ b/arch/x86/include/asm/preempt.h @@ -105,9 +105,9 @@ static __always_inline bool __preempt_count_dec_and_test(void) /* * Returns true when we need to resched and can (barring IRQ state). */ -static __always_inline bool should_resched(void) +static __always_inline bool should_resched(int preempt_offset) { - return unlikely(!__this_cpu_read_4(__preempt_count)); + return unlikely(__this_cpu_read_4(__preempt_count) == preempt_offset); } #ifdef CONFIG_PREEMPT diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h index 1cd3f5d767a81..54352f4dde1a4 100644 --- a/include/asm-generic/preempt.h +++ b/include/asm-generic/preempt.h @@ -74,9 +74,10 @@ static __always_inline bool __preempt_count_dec_and_test(void) /* * Returns true when we need to resched and can (barring IRQ state). */ -static __always_inline bool should_resched(void) +static __always_inline bool should_resched(int preempt_offset) { - return unlikely(!preempt_count() && tif_need_resched()); + return unlikely(preempt_count() == preempt_offset && + tif_need_resched()); } #ifdef CONFIG_PREEMPT diff --git a/include/linux/preempt.h b/include/linux/preempt.h index 1841b58cf1734..411a5c6371da8 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -22,7 +22,8 @@ #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER) extern void preempt_count_add(int val); extern void preempt_count_sub(int val); -#define preempt_count_dec_and_test() ({ preempt_count_sub(1); should_resched(); }) +#define preempt_count_dec_and_test() \ + ({ preempt_count_sub(1); should_resched(0); }) #else #define preempt_count_add(val) __preempt_count_add(val) #define preempt_count_sub(val) __preempt_count_sub(val) @@ -61,7 +62,7 @@ do { \ #define preempt_check_resched() \ do { \ - if (should_resched()) \ + if (should_resched(0)) \ __preempt_schedule(); \ } while (0) diff --git a/include/linux/preempt_mask.h b/include/linux/preempt_mask.h index 1f654ee836b7d..5cb25f17331a3 100644 --- a/include/linux/preempt_mask.h +++ b/include/linux/preempt_mask.h @@ -71,13 +71,21 @@ */ #define in_nmi() (preempt_count() & NMI_MASK) +/* + * The preempt_count offset after preempt_disable(); + */ #if defined(CONFIG_PREEMPT_COUNT) -# define PREEMPT_DISABLE_OFFSET 1 +# define PREEMPT_DISABLE_OFFSET PREEMPT_OFFSET #else -# define PREEMPT_DISABLE_OFFSET 0 +# define PREEMPT_DISABLE_OFFSET 0 #endif /* + * The preempt_count offset after spin_lock() + */ +#define PREEMPT_LOCK_OFFSET PREEMPT_DISABLE_OFFSET + +/* * The preempt_count offset needed for things like: * * spin_lock_bh() @@ -90,7 +98,7 @@ * * Work as expected. */ -#define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_DISABLE_OFFSET) +#define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_LOCK_OFFSET) /* * Are we running in atomic context? WARNING: this macro cannot diff --git a/include/linux/sched.h b/include/linux/sched.h index 91fe6a38b3076..ec6000f66e75b 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2647,12 +2647,6 @@ extern int _cond_resched(void); extern int __cond_resched_lock(spinlock_t *lock); -#ifdef CONFIG_PREEMPT_COUNT -#define PREEMPT_LOCK_OFFSET PREEMPT_OFFSET -#else -#define PREEMPT_LOCK_OFFSET 0 -#endif - #define cond_resched_lock(lock) ({ \ __might_sleep(__FILE__, __LINE__, PREEMPT_LOCK_OFFSET); \ __cond_resched_lock(lock); \ diff --git a/kernel/sched/core.c b/kernel/sched/core.c index a19262a7d70b3..bbe957762ace6 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4113,7 +4113,7 @@ static void __cond_resched(void) int __sched _cond_resched(void) { - if (should_resched()) { + if (should_resched(0)) { __cond_resched(); return 1; } @@ -4131,7 +4131,7 @@ EXPORT_SYMBOL(_cond_resched); */ int __cond_resched_lock(spinlock_t *lock) { - int resched = should_resched(); + int resched = should_resched(PREEMPT_LOCK_OFFSET); int ret = 0; lockdep_assert_held(lock); @@ -4153,7 +4153,7 @@ int __sched __cond_resched_softirq(void) { BUG_ON(!in_softirq()); - if (should_resched()) { + if (should_resched(SOFTIRQ_DISABLE_OFFSET)) { local_bh_enable(); __cond_resched(); local_bh_disable();