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Subject[PATCH tip/core/rcu 11/15] rcu: Avoid spurious RCU CPU stall warnings
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From: "Paul E. McKenney" <paul.mckenney@linaro.org>

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 <bgillbruce@gmail.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
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);
--
1.7.8


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