On 9/3/2022 10:04 AM, Paul E. McKenney wrote: > On Thu, Sep 01, 2022 at 10:17:06PM +0000, Joel Fernandes (Google) wrote: >> When the bypass cblist gets too big or its timeout has occurred, it is >> flushed into the main cblist. However, the bypass timer is still running >> and the behavior is that it would eventually expire and wake the GP >> thread. >> >> Since we are going to use the bypass cblist for lazy CBs, do the wakeup >> soon as the flush happens. Otherwise, the lazy-timer will go off much >> later and the now-non-lazy cblist CBs can get stranded for the duration >> of the timer. >> >> This is a good thing to do anyway (regardless of this series), since it >> makes the behavior consistent with behavior of other code paths where queueing >> something into the ->cblist makes the GP kthread in a non-sleeping state >> quickly. >> >> Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> >> --- >> kernel/rcu/tree_nocb.h | 8 +++++++- >> 1 file changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h >> index 0a5f0ef41484..31068dd31315 100644 >> --- a/kernel/rcu/tree_nocb.h >> +++ b/kernel/rcu/tree_nocb.h >> @@ -447,7 +447,13 @@ static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp, >> rcu_advance_cbs_nowake(rdp->mynode, rdp); >> rdp->nocb_gp_adv_time = j; >> } >> - rcu_nocb_unlock_irqrestore(rdp, flags); >> + >> + // The flush succeeded and we moved CBs into the ->cblist. >> + // However, the bypass timer might still be running. Wakeup the >> + // GP thread by calling a helper with was_all_done set so that >> + // wake up happens (needed if main CB list was empty before). >> + __call_rcu_nocb_wake(rdp, true, flags) > > TREE01 and TREE04 gripe about the missing ";". I added it. Sorry about that, I must have messed lost the semicolon during re-basing. - Joel
