Messages in this thread Patch in this message | | | Date | Sun, 20 Sep 2020 08:06:38 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 4/4] rcu/tree: Use schedule_delayed_work() instead of WQ_HIGHPRI queue |
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On Fri, Sep 18, 2020 at 09:48:17PM +0200, Uladzislau Rezki (Sony) wrote: > Recently the separate worker thread has been introduced to > maintain the local page cache from the regular kernel context, > instead of kvfree_rcu() contexts. That was done because a caller > of the k[v]free_rcu() can be any context type what is a problem > from the allocation point of view. > > >From the other hand, the lock-less way of obtaining a page has > been introduced and directly injected to the k[v]free_rcu() path. > > Therefore it is not important anymore to use a high priority "wq" > for the external job that used to fill a page cache ASAP when it > was empty. > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
And I needed to apply the patch below to make this one pass rcutorture scenarios SRCU-P and TREE05. Repeat by:
tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 3 --configs "SRCU-P TREE05" --trust-make
Without the patch below, the system hangs very early in boot.
Please let me know if some other fix would be better.
Thanx, Paul
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diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 8ce1ea4..2424e2a 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3481,7 +3481,8 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) success = kvfree_call_rcu_add_ptr_to_bulk(krcp, ptr); if (!success) { // Use delayed work, so we do not deadlock with rq->lock. - if (!atomic_xchg(&krcp->work_in_progress, 1)) + if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING && + !atomic_xchg(&krcp->work_in_progress, 1)) schedule_delayed_work(&krcp->page_cache_work, 1); if (head == NULL)
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