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FAILED: patch "[PATCH] sched/preempt: Fix cond_resched_lock() and" failed to apply to 3.14-stable tree

PATCH [email protected] 3 participants 3 messages Oct 18, 2015

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Stable branch x86 Scheduler Generic include/asm header files
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#0 lore raw

The patch below does not apply to the 3.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From fe32d3cd5e8eb0f82e459763374aa80797023403 Mon Sep 17 00:00:00 2001

From: Konstantin Khlebnikov <[email protected]>
Date: Wed, 15 Jul 2015 12:52:04 +0300
Subject: [PATCH] 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 <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Cc Alexander Graf <[email protected]>
Cc Boris Ostrovsky <[email protected]>
Cc David Vrabel <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Mike Galbraith <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Thomas Gleixner <[email protected]>
Fixes bdb438065890 ("sched: Extract the basic add/sub preempt_count modifiers")
Link http://lkml.kernel.org/r/20150715095204.12246.98268.stgit@buzz open here
Signed-off-by Ingo Molnar <[email protected]>
arch/x86/include/asm/preempt.h +2 -2
index dca71714f860..b12f81022a6b 100644
@@ -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
include/asm-generic/preempt.h +3 -2
index d0a7a4753db2..0bec580a4885 100644
@@ -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
include/linux/preempt.h +14 -5
index 84991f185173..bea8dd8ff5e0 100644
@@ -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)
include/linux/sched.h +0 -6
index 65a8a8651596..9c144657aace 100644
@@ -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);				\
kernel/sched/core.c +3 -3
index fa5826cc612f..f5fad2b12baf 100644
@@ -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();
#1 lore raw

Depends on 90b62b5129d5cb50f62f40e684de7a1961e57197. Rather than munge the patch, take the dependency.

Quoted 1 line

From 90b62b5129d5cb50f62f40e684de7a1961e57197 Mon Sep 17 00:00:00 2001

From: Frederic Weisbecker <[email protected]>
Date: Tue, 12 May 2015 16:41:48 +0200
Subject: sched/preempt: Rename PREEMPT_CHECK_OFFSET to PREEMPT_DISABLE_OFFSET

"CHECK" suggests it's only used as a comparison mask. But now it's used further as a config-conditional preempt disabler offset. Lets disambiguate this name.

Signed-off-by Frederic Weisbecker <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Thomas Gleixner <[email protected]>
Link http://lkml.kernel.org/r/[email protected] open here
Signed-off-by Ingo Molnar <[email protected]>
Signed-off-by Mike Galbraith <[email protected]>
---
 include/linux/preempt_mask.h |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
include/linux/preempt_mask.h +4 -4
@@ -72,9 +72,9 @@
 #define in_nmi()	(preempt_count() & NMI_MASK)
 
 #if defined(CONFIG_PREEMPT_COUNT)
-# define PREEMPT_CHECK_OFFSET 1
+# define PREEMPT_DISABLE_OFFSET 1
 #else
-# define PREEMPT_CHECK_OFFSET 0
+# define PREEMPT_DISABLE_OFFSET 0
 #endif
 
 /*

@@ -90,7 +90,7 @@
  *
  * Work as expected.
  */
-#define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_CHECK_OFFSET)
+#define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_DISABLE_OFFSET)
 
 /*
  * Are we running in atomic context?  WARNING: this macro cannot

@@ -106,7 +106,7 @@
  * (used by the scheduler, *after* releasing the kernel lock)
  */
 #define in_atomic_preempt_off() \
-		((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_CHECK_OFFSET)
+		((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_DISABLE_OFFSET)
 
 #ifdef CONFIG_PREEMPT_COUNT
 # define preemptible()	(preempt_count() == 0 && !irqs_disabled())
#2 lore raw
Quoted 1 line

From fe32d3cd5e8eb0f82e459763374aa80797023403 Mon Sep 17 00:00:00 2001

From: Konstantin Khlebnikov <[email protected]>
Date: Wed, 15 Jul 2015 12:52:04 +0300
Subject: 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 <[email protected]>
Signed-off-by Peter Zijlstra (Intel) <[email protected]>
Cc Alexander Graf <[email protected]>
Cc Boris Ostrovsky <[email protected]>
Cc David Vrabel <[email protected]>
Cc Linus Torvalds <[email protected]>
Cc Mike Galbraith <[email protected]>
Cc Paul Mackerras <[email protected]>
Cc Peter Zijlstra <[email protected]>
Cc Thomas Gleixner <[email protected]>
Fixes bdb438065890 ("sched: Extract the basic add/sub preempt_count modifiers")
Link http://lkml.kernel.org/r/20150715095204.12246.98268.stgit@buzz open here
Signed-off-by Ingo Molnar <[email protected]>
Signed-off-by Mike Galbraith <[email protected]>
---
 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(-)
arch/x86/include/asm/preempt.h +2 -2
@@ -105,9 +105,9 @@ static __always_inline bool __preempt_co
 /*
  * 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
include/asm-generic/preempt.h +3 -2
@@ -74,9 +74,10 @@ static __always_inline bool __preempt_co
 /*
  * 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
include/linux/preempt.h +3 -2
@@ -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)
include/linux/preempt_mask.h +11 -3
@@ -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
include/linux/sched.h +0 -6
@@ -2652,12 +2652,6 @@ 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);				\
kernel/sched/core.c +3 -3
@@ -4118,7 +4118,7 @@ static void __cond_resched(void)
 
 int __sched _cond_resched(void)
 {
-	if (should_resched()) {
+	if (should_resched(0)) {
 		__cond_resched();
 		return 1;
 	}

@@ -4136,7 +4136,7 @@ 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);

@@ -4158,7 +4158,7 @@ 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();