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Message-ID: <tip-fe32d3cd5e8eb0f82e459763374aa80797023403@git.kernel.org>
Date: Mon, 3 Aug 2015 10:08:22 -0700
From: tip-bot for Konstantin Khlebnikov <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: torvalds@...ux-foundation.org, paulus@...ba.org,
peterz@...radead.org, linux-kernel@...r.kernel.org, efault@....de,
hpa@...or.com, mingo@...nel.org, agraf@...e.de,
boris.ostrovsky@...cle.com, david.vrabel@...rix.com,
tglx@...utronix.de, khlebnikov@...dex-team.ru
Subject: [tip:sched/core] sched/preempt: Fix cond_resched_lock()
and cond_resched_softirq()
Commit-ID: fe32d3cd5e8eb0f82e459763374aa80797023403
Gitweb: http://git.kernel.org/tip/fe32d3cd5e8eb0f82e459763374aa80797023403
Author: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
AuthorDate: Wed, 15 Jul 2015 12:52:04 +0300
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 3 Aug 2015 12:21:24 +0200
sched/preempt: Fix cond_resched_lock() and cond_resched_softirq()
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 <khlebnikov@...dex-team.ru>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Alexander Graf <agraf@...e.de>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: David Vrabel <david.vrabel@...rix.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
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 <mingo@...nel.org>
---
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 dca7171..b12f810 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 d0a7a47..0bec580 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 84991f1..bea8dd8 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_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()
@@ -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 65a8a86..9c14465 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2891,12 +2891,6 @@ 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 fa5826c..f5fad2b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4496,7 +4496,7 @@ SYSCALL_DEFINE0(sched_yield)
int __sched _cond_resched(void)
{
- if (should_resched()) {
+ if (should_resched(0)) {
preempt_schedule_common();
return 1;
}
@@ -4514,7 +4514,7 @@ 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);
@@ -4536,7 +4536,7 @@ int __sched __cond_resched_softirq(void)
{
BUG_ON(!in_softirq());
- if (should_resched()) {
+ if (should_resched(SOFTIRQ_DISABLE_OFFSET)) {
local_bh_enable();
preempt_schedule_common();
local_bh_disable();
--
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