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From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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,
	edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com,
	sbw@mit.edu, patches@linaro.org,
	"Paul E. McKenney" <paul.mckenney@linaro.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 4/5] rcu: Fix precedence error in cpu_needs_another_gp()
Date: Tue, 30 Oct 2012 10:19:22 -0700	[thread overview]
Message-ID: <1351617563-28506-4-git-send-email-paulmck@linux.vnet.ibm.com> (raw)
In-Reply-To: <1351617563-28506-1-git-send-email-paulmck@linux.vnet.ibm.com>

From: "Paul E. McKenney" <paul.mckenney@linaro.org>

The fix introduced by a10d206e (rcu: Fix day-one dyntick-idle
stall-warning bug) has a C-language precedence error.  It turns out
that this error is harmless in that the same result is computed for all
inputs, but the code is nevertheless a potential source of confusion.
This commit therefore introduces parentheses in order to force the
execution of the code to reflect the intent.

Reported-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcutree.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index f9c17c3..effd47a 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -313,7 +313,7 @@ static int
 cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
 {
 	return *rdp->nxttail[RCU_DONE_TAIL +
-			     ACCESS_ONCE(rsp->completed) != rdp->completed] &&
+			     (ACCESS_ONCE(rsp->completed) != rdp->completed)] &&
 	       !rcu_gp_in_progress(rsp);
 }
 
-- 
1.7.8


  parent reply	other threads:[~2012-10-30 17:33 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-30 17:19 [PATCH tip/core/rcu 0/5] Idle changes for 3.8 Paul E. McKenney
2012-10-30 17:19 ` [PATCH tip/core/rcu 1/5] rcu: Remove rcu_switch() Paul E. McKenney
2012-10-30 17:19   ` [PATCH tip/core/rcu 2/5] rcu: Update RCU_FAST_NO_HZ help text Paul E. McKenney
2012-10-30 17:19   ` [PATCH tip/core/rcu 3/5] rcu: Add a module parameter to force use of expedited RCU primitives Paul E. McKenney
2012-10-30 17:19   ` Paul E. McKenney [this message]
2012-10-30 17:19   ` [PATCH tip/core/rcu 5/5] rcu: Wordsmith help text for RCU_USER_QS kernel parameter Paul E. McKenney

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