The following commit has been merged into the core/rcu branch of tip:
Commit-ID: 9c39245382de4d52a122641952900709d4a9950b
Gitweb: https://git.kernel.org/tip/9c39245382de4d52a122641952900709d4a9950b
Author: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
AuthorDate: Mon, 22 Jun 2020 00:07:27 +05:30
Committer: Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Mon, 24 Aug 2020 18:36:05 -07:00
rcu/tree: Force quiescent state on callback overload
On callback overload, it is necessary to quickly detect idle CPUs,
and rcu_gp_fqs_check_wake() checks for this condition. Unfortunately,
the code following the call to this function does not repeat this check,
which means that in reality no actual quiescent-state forcing, instead
only a couple of quick and pointless wakeups at the beginning of the
grace period.
This commit therefore adds a check for the RCU_GP_FLAG_OVLD flag in
the post-wakeup "if" statement in rcu_gp_fqs_loop().
Fixes: 1fca4d12f4637 ("rcu: Expedite first two FQS scans under callback-overload conditions")
Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Signed-off-by: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
kernel/rcu/tree.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8969120..4770d77 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1884,7 +1884,7 @@ static void rcu_gp_fqs_loop(void)
break;
/* If time for quiescent-state forcing, do it. */
if (!time_after(rcu_state.jiffies_force_qs, jiffies) ||
- (gf & RCU_GP_FLAG_FQS)) {
+ (gf & (RCU_GP_FLAG_FQS | RCU_GP_FLAG_OVLD))) {
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("fqsstart"));
rcu_gp_fqs(first_gp_fqs);
|