From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 494E9C4CEC4 for ; Mon, 23 Sep 2019 19:24:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 254C720B7C for ; Mon, 23 Sep 2019 19:24:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2440443AbfIWTYB (ORCPT ); Mon, 23 Sep 2019 15:24:01 -0400 Received: from mx2.suse.de ([195.135.220.15]:54494 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2440392AbfIWTYB (ORCPT ); Mon, 23 Sep 2019 15:24:01 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 2F23CAD72; Mon, 23 Sep 2019 19:23:59 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 23 Sep 2019 21:23:57 +0200 From: Roman Penyaev To: Jason Baron Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Davidlohr Bueso , Al Viro , Eric Wong Subject: Re: [PATCH] epoll: simplify ep_poll_safewake() for CONFIG_DEBUG_LOCK_ALLOC In-Reply-To: References: <1567628549-11501-1-git-send-email-jbaron@akamai.com> Message-ID: <1b26e25fcc0e6c54cbdb9e66dade17db@suse.de> X-Sender: rpenyaev@suse.de User-Agent: Roundcube Webmail Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >> Cc: Davidlohr Bueso >> Cc: Roman Penyaev >> Cc: Al Viro >> Cc: Eric Wong >> Cc: Andrew Morton >> --- >> 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 -- Roman