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McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org, "Paul E. McKenney" Subject: [PATCH RFC tip/core/rcu 02/41] rcu: Improve synchronize_rcu() diagnostics Date: Wed, 1 Feb 2012 11:41:20 -0800 Message-Id: <1328125319-5205-2-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.8 In-Reply-To: <1328125319-5205-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120201194131.GA10028@linux.vnet.ibm.com> <1328125319-5205-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12020119-5806-0000-0000-000011F303C6 From: Frederic Weisbecker Although TREE_PREEMPT_RCU indirectly uses might_sleep() to detect illegal use of synchronize_sched() and synchronize_rcu_bh() from within an RCU read-side critical section, this might_sleep() check is bypassed when there is only a single CPU (for example, when running an SMP kernel on a single-CPU system). This patch therefore adds a might_sleep() call to the rcu_blocking_is_gp() check that is unconditionally invoked from both synchronize_sched() and synchronize_rcu_bh(). Signed-off-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney --- include/linux/rcutree.h | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 6745846..73e7195 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -83,6 +83,7 @@ extern void rcu_sched_force_quiescent_state(void); /* A context switch is a grace period for RCU-sched and RCU-bh. */ static inline int rcu_blocking_is_gp(void) { + might_sleep(); /* Check for RCU read-side critical section. */ return num_online_cpus() == 1; }