Messages in this thread | | | Date | Mon, 23 Sep 2019 21:23:57 +0200 | From | Roman Penyaev <> | Subject | Re: [PATCH] epoll: simplify ep_poll_safewake() for CONFIG_DEBUG_LOCK_ALLOC |
| |
On 2019-09-23 17:43, Jason Baron wrote: > On 9/4/19 4:22 PM, Jason Baron wrote: >> Currently, ep_poll_safewake() in the CONFIG_DEBUG_LOCK_ALLOC case uses >> ep_call_nested() in order to pass the correct subclass argument to >> spin_lock_irqsave_nested(). However, ep_call_nested() adds unnecessary >> checks for epoll depth and loops that are already verified when doing >> EPOLL_CTL_ADD. This mirrors a conversion that was done for >> !CONFIG_DEBUG_LOCK_ALLOC in: commit 37b5e5212a44 ("epoll: remove >> ep_call_nested() from ep_eventpoll_poll()") >> >> Signed-off-by: Jason Baron <jbaron@akamai.com> >> Cc: Davidlohr Bueso <dave@stgolabs.net> >> Cc: Roman Penyaev <rpenyaev@suse.de> >> Cc: Al Viro <viro@zeniv.linux.org.uk> >> Cc: Eric Wong <normalperson@yhbt.net> >> Cc: Andrew Morton <akpm@linux-foundation.org> >> --- >> fs/eventpoll.c | 36 +++++++++++++----------------------- >> 1 file changed, 13 insertions(+), 23 deletions(-) >> >> diff --git a/fs/eventpoll.c b/fs/eventpoll.c >> index d7f1f50..a9b2737 100644 >> --- a/fs/eventpoll.c >> +++ b/fs/eventpoll.c >> @@ -551,28 +551,23 @@ static int ep_call_nested(struct nested_calls >> *ncalls, >> */ >> #ifdef CONFIG_DEBUG_LOCK_ALLOC >> >> -static struct nested_calls poll_safewake_ncalls; >> - >> -static int ep_poll_wakeup_proc(void *priv, void *cookie, int >> call_nests) >> -{ >> - unsigned long flags; >> - wait_queue_head_t *wqueue = (wait_queue_head_t *)cookie; >> - >> - spin_lock_irqsave_nested(&wqueue->lock, flags, call_nests + 1); >> - wake_up_locked_poll(wqueue, EPOLLIN); >> - spin_unlock_irqrestore(&wqueue->lock, flags); >> - >> - return 0; >> -} >> +static DEFINE_PER_CPU(int, wakeup_nest); >> >> static void ep_poll_safewake(wait_queue_head_t *wq) >> { >> - int this_cpu = get_cpu(); >> - >> - ep_call_nested(&poll_safewake_ncalls, >> - ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu); >> + unsigned long flags; >> + int subclass; >> >> - put_cpu(); >> + local_irq_save(flags); >> + preempt_disable(); >> + subclass = __this_cpu_read(wakeup_nest); >> + spin_lock_nested(&wq->lock, subclass + 1); >> + __this_cpu_inc(wakeup_nest); >> + wake_up_locked_poll(wq, POLLIN); >> + __this_cpu_dec(wakeup_nest); >> + spin_unlock(&wq->lock); >> + local_irq_restore(flags); >> + preempt_enable(); >> }
What if reduce number of lines with something as the following:
int this_cpu = get_cpu(); subclass = __this_cpu_inc_return(wakeup_nest); spin_lock_irqsave_nested(&wq->lock, flags, subclass); wake_up_locked_poll(wq, POLLIN); spin_unlock_irqrestore(&wq->lock, flags); __this_cpu_dec(wakeup_nest); put_cpu();
Other than that looks good to me.
Reviewed-by: Roman Penyaev <rpenyaev@suse.de>
-- Roman
| |