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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, sbw@mit.edu, patches@linaro.org, "Paul E. McKenney" , "Paul E. McKenney" Subject: [PATCH tip/core/rcu 11/15] rcu: Avoid spurious RCU CPU stall warnings Date: Thu, 30 Aug 2012 11:56:24 -0700 Message-Id: <1346352988-32444-11-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.8 In-Reply-To: <1346352988-32444-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20120830185607.GA32148@linux.vnet.ibm.com> <1346352988-32444-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12083021-4242-0000-0000-000002BA0795 X-Gm-Message-State: ALoCoQl7r/OtgSpD2uowEhVRucjzC9rhhMyu3vVH8colrzNZR9q7BS05pQhjP7dKhA/lRf92CuSx From: "Paul E. McKenney" If a given CPU avoids the idle loop but also avoids starting a new RCU grace period for a full minute, RCU can issue spurious RCU CPU stall warnings. This commit fixes this issue by adding a check for ongoing grace period to avoid these spurious stall warnings. Reported-by: Becky Bruce Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/rcutree.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/kernel/rcutree.c b/kernel/rcutree.c index fbe43b0..e58097b 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -820,7 +820,8 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) j = ACCESS_ONCE(jiffies); js = ACCESS_ONCE(rsp->jiffies_stall); rnp = rdp->mynode; - if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) { + if (rcu_gp_in_progress(rsp) && + (ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) { /* We haven't checked in, so go dump stack. */ print_cpu_stall(rsp);