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 khlebni...@yandex-team.ru
---
arch/x86/include/asm/preempt.h |4 ++--
include/asm-generic/preempt.h |5 +++--
include/linux/preempt.h| 19 ++-
include/linux/sched.h |6 --
kernel/sched/core.c|6 +++---
5 files changed, 22 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index dca71714f860..b12f81022a6b 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -90,9 +90,9 @@ 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(!raw_cpu_read_4(__preempt_count));
+ return unlikely(raw_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 d0a7a4753db2..0bec580a4885 100644
--- a/include/asm-generic/preempt.h
+++ b/include/asm-generic/preempt.h
@@ -71,9 +71,10 @@ 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 84991f185173..bea8dd8ff5e0 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -84,13 +84,21 @@
*/
#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_OFFSETPREEMPT_OFFSET
#else
-# define PREEMPT_DISABLE_OFFSET 0
+# define PREEMPT_DISABLE_OFFSET0
#endif
/*
+ * The preempt_count offset after spin_lock()
+ */
+#define PREEMPT_LOCK_OFFSETPREEMPT_DISABLE_OFFSET
+
+/*
* The preempt_count offset needed for things like:
*
* spin_lock_bh()
@@ -103,7 +111,7 @@
*
* 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
@@ -124,7 +132,8 @@
#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)
@@ -184,7 +193,7 @@ do { \
#define preempt_check_resched() \
do { \
- if (should_resched()) \
+ if (should_resched(0)) \
__preempt_schedule(); \
} while (0)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index ae21f1591615..a8e9b17acdee 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2885,12 +2885,6 @@ extern int _cond_resched(void);
extern int __cond_resched_lock(spinlock_t *lock);
-#ifdef CONFIG_PREEMPT_COUNT
-#define PREEMPT_LOCK_OFFSETPREEMPT_OFFSET
-#else
-#define PREEMPT_LOCK_OFFSET0
-#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 78b4bad10081..d9a4d93dc879 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4492,7 +4492,7 @@ SYSCALL_DEFINE0(sched_yield)
int __sched _cond_resched(void)
{
- if (should_resched()) {
+ if (should_resched(0)) {
preempt_schedule_common();
return 1;
}
@@ -4510,7 +4510,7 @@ EXPORT_SYMBOL(_cond_resched);
*/
int __cond_resched_lock(spinlock_t *lock)
{
- int resched = should_resched();
+ int resched =
