From: Joel Fernandes (Google) Date: Fri, 16 Aug 2019 02:59:14 +0000 (-0400) Subject: rcu: Ensure that ->rcu_urgent_qs is set before resched IPI X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=05ef9e9eb3dade21413680f41eb0170778e8ae2b;p=linux.git rcu: Ensure that ->rcu_urgent_qs is set before resched IPI The RCU-specific resched_cpu() function sends a resched IPI to the specified CPU, which can be used to force the tick on for a given nohz_full CPU. This is needed when this nohz_full CPU is looping in the kernel while blocking the current grace period. However, for the tick to actually be forced on in all cases, that CPU's rcu_data structure's ->rcu_urgent_qs flag must be set beforehand. This commit therefore causes rcu_implicit_dynticks_qs() to set this flag prior to invoking resched_cpu() on a holdout nohz_full CPU. Signed-off-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney --- diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 81105141b6a82..0d83b1944e198 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1073,6 +1073,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) if (tick_nohz_full_cpu(rdp->cpu) && time_after(jiffies, READ_ONCE(rdp->last_fqs_resched) + jtsq * 3)) { + WRITE_ONCE(*ruqp, true); resched_cpu(rdp->cpu); WRITE_ONCE(rdp->last_fqs_resched, jiffies); }