Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752454AbbK1QKy (ORCPT ); Sat, 28 Nov 2015 11:10:54 -0500 Received: from www262.sakura.ne.jp ([202.181.97.72]:32579 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752223AbbK1QKS (ORCPT ); Sat, 28 Nov 2015 11:10:18 -0500 To: mhocko@kernel.org, linux-mm@kvack.org Cc: akpm@linux-foundation.org, torvalds@linux-foundation.org, mgorman@suse.de, rientjes@google.com, riel@redhat.com, hughd@google.com, oleg@redhat.com, andrea@kernel.org, linux-kernel@vger.kernel.org, mhocko@suse.com Subject: Re: [RFC PATCH -v2] mm, oom: introduce oom reaper From: Tetsuo Handa References: <1448467018-20603-1-git-send-email-mhocko@kernel.org> <1448640772-30147-1-git-send-email-mhocko@kernel.org> <201511281339.JHH78172.SLOQFOFHVFOMJt@I-love.SAKURA.ne.jp> In-Reply-To: <201511281339.JHH78172.SLOQFOFHVFOMJt@I-love.SAKURA.ne.jp> Message-Id: <201511290110.FJB87096.OHJLVQOSFFtMFO@I-love.SAKURA.ne.jp> X-Mailer: Winbiff [Version 2.51 PL2] X-Accept-Language: ja,en,zh Date: Sun, 29 Nov 2015 01:10:10 +0900 Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1905 Lines: 53 Tetsuo Handa wrote: > > Users of mmap_sem which need it for write should be carefully reviewed > > to use _killable waiting as much as possible and reduce allocations > > requests done with the lock held to absolute minimum to reduce the risk > > even further. > > It will be nice if we can have down_write_killable()/down_read_killable(). It will be nice if we can also have __GFP_KILLABLE. Although currently it can't be perfect because reclaim functions called from __alloc_pages_slowpath() use unkillable waits, starting from just bail out as with __GFP_NORETRY when fatal_signal_pending(current) is true will be helpful. So far I'm hitting no problem with testers except the one using mmap()/munmap(). I think that cmpxchg() was not needed. diff --git a/mm/oom_kill.c b/mm/oom_kill.c index c2ab7f9..1a65739 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -483,8 +483,6 @@ static int oom_reaper(void *unused) static void wake_oom_reaper(struct mm_struct *mm) { - struct mm_struct *old_mm; - if (!oom_reaper_th) return; @@ -492,14 +490,15 @@ static void wake_oom_reaper(struct mm_struct *mm) * Make sure that only a single mm is ever queued for the reaper * because multiple are not necessary and the operation might be * disruptive so better reduce it to the bare minimum. + * Caller is serialized by oom_lock mutex. */ - old_mm = cmpxchg(&mm_to_reap, NULL, mm); - if (!old_mm) { + if (!mm_to_reap) { /* * Pin the given mm. Use mm_count instead of mm_users because * we do not want to delay the address space tear down. */ atomic_inc(&mm->mm_count); + mm_to_reap = mm; wake_up(&oom_reaper_wait); } } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/