Le Tue, Jun 04, 2024 at 03:23:49PM -0700, Paul E. McKenney a écrit : > From: "Joel Fernandes (Google)" <[email protected]> > > In the synchronize_rcu() common case, we will have less than > SR_MAX_USERS_WAKE_FROM_GP number of users per GP. Waking up the kworker > is pointless just to free the last injected wait head since at that point, > all the users have already been awakened. > > Introduce a new counter to track this and prevent the wakeup in the > common case. > > Signed-off-by: Joel Fernandes (Google) <[email protected]> > Reviewed-by: Uladzislau Rezki (Sony) <[email protected]> > Signed-off-by: Paul E. McKenney <[email protected]> > --- > kernel/rcu/tree.c | 35 ++++++++++++++++++++++++++++++----- > kernel/rcu/tree.h | 1 + > 2 files changed, 31 insertions(+), 5 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 6ba36d9c09bde..2fe08e6186b4d 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -96,6 +96,7 @@ static struct rcu_state rcu_state = { > .ofl_lock = __ARCH_SPIN_LOCK_UNLOCKED, > .srs_cleanup_work = __WORK_INITIALIZER(rcu_state.srs_cleanup_work, > rcu_sr_normal_gp_cleanup_work), > + .srs_cleanups_pending = ATOMIC_INIT(0), > }; > > /* Dump rcu_node combining tree at boot to verify correct setup. */ > @@ -1633,8 +1634,11 @@ static void rcu_sr_normal_gp_cleanup_work(struct > work_struct *work) > * the done tail list manipulations are protected here. > */ > done = smp_load_acquire(&rcu_state.srs_done_tail); > - if (!done) > + if (!done) { > + /* See comments below. */ > + atomic_dec_return_release(&rcu_state.srs_cleanups_pending);
This condition is not supposed to happen. If the work is scheduled, there has to be a wait_queue in rcu_state.srs_done_tail. And decrementing may make things worse. So this should be: if (WARN_ON_ONCE(!done)) return; Thanks.
