From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Baron Subject: Re: [PATCH 1/2] sched/wait: add round robin wakeup mode Date: Mon, 09 Feb 2015 23:06:17 -0500 Message-ID: <54D983B9.800@akamai.com> References: <20150209215045.GU21418@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: mingo@redhat.com, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, normalperson@yhbt.net, davidel@xmailserver.org, mtk.manpages@gmail.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Peter Zijlstra Return-path: In-Reply-To: <20150209215045.GU21418@twins.programming.kicks-ass.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 02/09/2015 04:50 PM, Peter Zijlstra wrote: > On Mon, Feb 09, 2015 at 08:05:57PM +0000, Jason Baron wrote: >> diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c >> index 852143a..17d1039 100644 >> --- a/kernel/sched/wait.c >> +++ b/kernel/sched/wait.c >> @@ -71,8 +71,11 @@ static void __wake_up_common(wait_queue_head_t *q, unsigned int mode, >> unsigned flags = curr->flags; >> >> if (curr->func(curr, mode, wake_flags, key) && >> - (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive) >> + (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive) { >> + if (flags & WQ_FLAG_ROUND_ROBIN) >> + list_move_tail(&curr->task_list, &q->task_list); >> break; >> + } >> } >> } > I think you meant to write something like: > > if (curr->func(curr, mode, wake_flags, key) && > (flags & WQ_FLAG_EXCLUSIVE)) { > if (flag & WQ_FLAG_ROUND_ROBIN) > list_move_tail(&curr->task_list, &q->task_list); > if (!--nr_exclusive) > break; > } > > Otherwise can only work for nr_exclusive==1. Indeed. I'm also wondering if its worth avoiding the list_move_tail() for the case where nr_exclusive is initially 0. IE the wake all case, where we are just going to end up doing a bunch of list_move_tail() calls, but end up in the same state. Thanks, -Jason