Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757301Ab1FJNag (ORCPT ); Fri, 10 Jun 2011 09:30:36 -0400 Received: from mail-qw0-f46.google.com ([209.85.216.46]:40858 "EHLO mail-qw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757067Ab1FJNac (ORCPT ); Fri, 10 Jun 2011 09:30:32 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=heLKHcpk42oA1KMTWDuKDSamVMZI7Wl/dNWLngunFp3hBWaefwHEIwKfUhAw1ryNFj xY83ZQKA1/AW856BTe1Z+m+M0R8GBP+FADpl01Cv0o38NArgEz56XmT9kv9j6UV52M2W Lh6fWCV0dyThymaxlVVCiIgk9urSWYWuFjD6U= From: Frederic Weisbecker To: Ingo Molnar Cc: LKML , Frederic Weisbecker , Peter Zijlstra Subject: [PATCH 2/4] sched: Isolate preempt counting in its own config option Date: Fri, 10 Jun 2011 15:30:20 +0200 Message-Id: <1307712622-11104-3-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1307712622-11104-1-git-send-email-fweisbec@gmail.com> References: <1307712622-11104-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7288 Lines: 244 Create a new CONFIG_PREEMPT_COUNT that handles the inc/dec of preempt count offset independently. So that the offset can be updated by preempt_disable() and preempt_enable() even without the need for CONFIG_PREEMPT beeing set. This prepares to make CONFIG_DEBUG_SPINLOCK_SLEEP working with !CONFIG_PREEMPT where it currently doesn't detect code that sleeps inside explicit preemption disabled sections. Signed-off-by: Frederic Weisbecker Acked-by: Paul E. McKenney Cc: Ingo Molnar Cc: Peter Zijlstra --- include/linux/bit_spinlock.h | 2 +- include/linux/hardirq.h | 4 ++-- include/linux/pagemap.h | 4 ++-- include/linux/preempt.h | 26 +++++++++++++++++--------- include/linux/rcupdate.h | 12 ++++++------ include/linux/sched.h | 2 +- kernel/Kconfig.preempt | 3 +++ kernel/sched.c | 2 +- 8 files changed, 33 insertions(+), 22 deletions(-) diff --git a/include/linux/bit_spinlock.h b/include/linux/bit_spinlock.h index b4326bf..564d997 100644 --- a/include/linux/bit_spinlock.h +++ b/include/linux/bit_spinlock.h @@ -88,7 +88,7 @@ static inline int bit_spin_is_locked(int bitnum, unsigned long *addr) { #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) return test_bit(bitnum, addr); -#elif defined CONFIG_PREEMPT +#elif defined CONFIG_PREEMPT_COUNT return preempt_count(); #else return 1; diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index ba36217..f743883f 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -93,7 +93,7 @@ */ #define in_nmi() (preempt_count() & NMI_MASK) -#if defined(CONFIG_PREEMPT) +#if defined(CONFIG_PREEMPT_COUNT) # define PREEMPT_CHECK_OFFSET 1 #else # define PREEMPT_CHECK_OFFSET 0 @@ -115,7 +115,7 @@ #define in_atomic_preempt_off() \ ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_CHECK_OFFSET) -#ifdef CONFIG_PREEMPT +#ifdef CONFIG_PREEMPT_COUNT # define preemptible() (preempt_count() == 0 && !irqs_disabled()) # define IRQ_EXIT_OFFSET (HARDIRQ_OFFSET-1) #else diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 716875e..8e38d4c 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -134,7 +134,7 @@ static inline int page_cache_get_speculative(struct page *page) VM_BUG_ON(in_interrupt()); #if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU) -# ifdef CONFIG_PREEMPT +# ifdef CONFIG_PREEMPT_COUNT VM_BUG_ON(!in_atomic()); # endif /* @@ -172,7 +172,7 @@ static inline int page_cache_add_speculative(struct page *page, int count) VM_BUG_ON(in_interrupt()); #if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU) -# ifdef CONFIG_PREEMPT +# ifdef CONFIG_PREEMPT_COUNT VM_BUG_ON(!in_atomic()); # endif VM_BUG_ON(page_count(page) == 0); diff --git a/include/linux/preempt.h b/include/linux/preempt.h index 2e681d9..58969b2 100644 --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -27,6 +27,21 @@ asmlinkage void preempt_schedule(void); +#define preempt_check_resched() \ +do { \ + if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \ + preempt_schedule(); \ +} while (0) + +#else /* !CONFIG_PREEMPT */ + +#define preempt_check_resched() do { } while (0) + +#endif /* CONFIG_PREEMPT */ + + +#ifdef CONFIG_PREEMPT_COUNT + #define preempt_disable() \ do { \ inc_preempt_count(); \ @@ -39,12 +54,6 @@ do { \ dec_preempt_count(); \ } while (0) -#define preempt_check_resched() \ -do { \ - if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \ - preempt_schedule(); \ -} while (0) - #define preempt_enable() \ do { \ preempt_enable_no_resched(); \ @@ -80,18 +89,17 @@ do { \ preempt_check_resched(); \ } while (0) -#else +#else /* !CONFIG_PREEMPT_COUNT */ #define preempt_disable() do { } while (0) #define preempt_enable_no_resched() do { } while (0) #define preempt_enable() do { } while (0) -#define preempt_check_resched() do { } while (0) #define preempt_disable_notrace() do { } while (0) #define preempt_enable_no_resched_notrace() do { } while (0) #define preempt_enable_notrace() do { } while (0) -#endif +#endif /* CONFIG_PREEMPT_COUNT */ #ifdef CONFIG_PREEMPT_NOTIFIERS diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 99f9aa7..8f4f881 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -239,7 +239,7 @@ extern int rcu_read_lock_bh_held(void); * Check debug_lockdep_rcu_enabled() to prevent false positives during boot * and while lockdep is disabled. */ -#ifdef CONFIG_PREEMPT +#ifdef CONFIG_PREEMPT_COUNT static inline int rcu_read_lock_sched_held(void) { int lockdep_opinion = 0; @@ -250,12 +250,12 @@ static inline int rcu_read_lock_sched_held(void) lockdep_opinion = lock_is_held(&rcu_sched_lock_map); return lockdep_opinion || preempt_count() != 0 || irqs_disabled(); } -#else /* #ifdef CONFIG_PREEMPT */ +#else /* #ifdef CONFIG_PREEMPT_COUNT */ static inline int rcu_read_lock_sched_held(void) { return 1; } -#endif /* #else #ifdef CONFIG_PREEMPT */ +#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ @@ -276,17 +276,17 @@ static inline int rcu_read_lock_bh_held(void) return 1; } -#ifdef CONFIG_PREEMPT +#ifdef CONFIG_PREEMPT_COUNT static inline int rcu_read_lock_sched_held(void) { return preempt_count() != 0 || irqs_disabled(); } -#else /* #ifdef CONFIG_PREEMPT */ +#else /* #ifdef CONFIG_PREEMPT_COUNT */ static inline int rcu_read_lock_sched_held(void) { return 1; } -#endif /* #else #ifdef CONFIG_PREEMPT */ +#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */ #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ diff --git a/include/linux/sched.h b/include/linux/sched.h index 483c1ed..4ecd5cb 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2502,7 +2502,7 @@ extern int _cond_resched(void); extern int __cond_resched_lock(spinlock_t *lock); -#ifdef CONFIG_PREEMPT +#ifdef CONFIG_PREEMPT_COUNT #define PREEMPT_LOCK_OFFSET PREEMPT_OFFSET #else #define PREEMPT_LOCK_OFFSET 0 diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt index bf987b9..24e7cb0 100644 --- a/kernel/Kconfig.preempt +++ b/kernel/Kconfig.preempt @@ -35,6 +35,7 @@ config PREEMPT_VOLUNTARY config PREEMPT bool "Preemptible Kernel (Low-Latency Desktop)" + select PREEMPT_COUNT help This option reduces the latency of the kernel by making all kernel code (that is not executing in a critical section) @@ -52,3 +53,5 @@ config PREEMPT endchoice +config PREEMPT_COUNT + bool \ No newline at end of file diff --git a/kernel/sched.c b/kernel/sched.c index 01d9536..90ad7cf 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2843,7 +2843,7 @@ void sched_fork(struct task_struct *p) #if defined(CONFIG_SMP) p->on_cpu = 0; #endif -#ifdef CONFIG_PREEMPT +#ifdef CONFIG_PREEMPT_COUNT /* Want to start with kernel preemption disabled. */ task_thread_info(p)->preempt_count = 1; 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