Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933352AbbKMKN6 (ORCPT ); Fri, 13 Nov 2015 05:13:58 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:49154 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932715AbbKMKNy (ORCPT ); Fri, 13 Nov 2015 05:13:54 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Konstantin Khlebnikov , "Peter Zijlstra (Intel)" , Alexander Graf , Boris Ostrovsky , David Vrabel , Linus Torvalds , Mike Galbraith , Paul Mackerras , Thomas Gleixner , Ingo Molnar , Luis Henriques Subject: [PATCH 3.16.y-ckt 94/94] sched/preempt: Fix cond_resched_lock() and cond_resched_softirq() Date: Fri, 13 Nov 2015 10:10:28 +0000 Message-Id: <1447409428-12178-95-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1447409428-12178-1-git-send-email-luis.henriques@canonical.com> References: <1447409428-12178-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6523 Lines: 193 3.16.7-ckt20 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Konstantin Khlebnikov 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 [ luis: backported to 3.16: - some of the changes done in preempt_mask.h instead of preempt.h - adjusted context ] Signed-off-by: Luis Henriques --- 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 7024c12f7bfe..cebe6d05891e 100644 --- a/arch/x86/include/asm/preempt.h +++ b/arch/x86/include/asm/preempt.h @@ -93,9 +93,9 @@ 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 1cd3f5d767a8..54352f4dde1a 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 de83b4eb1642..8cd6725c5758 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -20,7 +20,8 @@ #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) @@ -59,7 +60,7 @@ 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 1f654ee836b7..5cb25f17331a 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 4bab946551e9..a632aaad1e59 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2736,12 +2736,6 @@ 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 c1d7818dade9..c80729679806 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4172,7 +4172,7 @@ static void __cond_resched(void) int __sched _cond_resched(void) { - if (should_resched()) { + if (should_resched(0)) { __cond_resched(); return 1; } @@ -4190,7 +4190,7 @@ 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); @@ -4212,7 +4212,7 @@ 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(); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/