From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758511AbZLNWol (ORCPT ); Mon, 14 Dec 2009 17:44:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753499AbZLNWoj (ORCPT ); Mon, 14 Dec 2009 17:44:39 -0500 Received: from mail-ew0-f219.google.com ([209.85.219.219]:44392 "EHLO mail-ew0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750859AbZLNWoi (ORCPT ); Mon, 14 Dec 2009 17:44:38 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer; b=iGbayrd6mfBgnx7elkcsX1DVuPgy5toBH6Q+ccWqGIYQc57xz/e6Lg2eno4aqsOj7/ YUAvyzxVky37O07wfoYu/A3dgIF8o6CBRbLdq6rYG6auvIbE96twQWjr8z6i+PAc8UCr vwj6xCQRRnUEHjtxesozxv57o1ElCjefC1s7Q= From: Frederic Weisbecker To: Ingo Molnar Cc: LKML , Frederic Weisbecker , "Paul E. McKenney" , Peter Zijlstra Subject: [PATCH] sched: Teach might_sleep about preemptable rcu Date: Mon, 14 Dec 2009 23:44:32 +0100 Message-Id: <1260830672-7166-1-git-send-regression-fweisbec@gmail.com> X-Mailer: git-send-email 1.6.2.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In practice, it is harmless to voluntarily sleep in a rcu_read_lock() section if we are running under preempt rcu, but it is illegal because if we build a kernel running non-preemptable rcu. Currently, might_sleep() doesn't notice sleepable operations under rcu_read_lock() sections if we are running under preemptable rcu because preempt_count() is left untouched after rcu_read_lock() in this case. But we want developers who test their changes under such config to notice the "sleeping while atomic" issues. Then we add rcu_read_lock_nesting to prempt_count() in might_sleep() checks. Signed-off-by: Frederic Weisbecker Cc: "Paul E. McKenney" Cc: Peter Zijlstra --- include/linux/rcutree.h | 11 +++++++++++ kernel/sched.c | 2 +- 2 files changed, 12 insertions(+), 1 deletions(-) diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index c93eee5..8044b1b 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -45,6 +45,12 @@ extern void __rcu_read_unlock(void); extern void synchronize_rcu(void); extern void exit_rcu(void); +/* + * Defined as macro as it is a very low level header + * included from areas that don't even know about current + */ +#define rcu_preempt_depth() (current->rcu_read_lock_nesting) + #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ static inline void __rcu_read_lock(void) @@ -63,6 +69,11 @@ static inline void exit_rcu(void) { } +static inline int rcu_preempt_depth(void) +{ + return 0; +} + #endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ static inline void __rcu_read_lock_bh(void) diff --git a/kernel/sched.c b/kernel/sched.c index ab42754..586c82c 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -9658,7 +9658,7 @@ void __init sched_init(void) #ifdef CONFIG_DEBUG_SPINLOCK_SLEEP static inline int preempt_count_equals(int preempt_offset) { - int nested = preempt_count() & ~PREEMPT_ACTIVE; + int nested = (preempt_count() & ~PREEMPT_ACTIVE) + rcu_preempt_depth(); return (nested == PREEMPT_INATOMIC_BASE + preempt_offset); } -- 1.6.2.3