From: Neeraj Upadhyay neeraju@codeaurora.org
[ Upstream commit 9c39245382de4d52a122641952900709d4a9950b ]
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@joelfernandes.org Signed-off-by: Neeraj Upadhyay neeraju@codeaurora.org Signed-off-by: Paul E. McKenney paulmck@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 1e9e500ff7906..572a79b1a8510 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1882,7 +1882,7 @@ 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);