From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f51.google.com (mail-wm0-f51.google.com [74.125.82.51]) by kanga.kvack.org (Postfix) with ESMTP id 91E41828E6 for ; Wed, 3 Feb 2016 08:18:59 -0500 (EST) Received: by mail-wm0-f51.google.com with SMTP id l66so163261487wml.0 for ; Wed, 03 Feb 2016 05:18:59 -0800 (PST) Received: from mail-wm0-x22c.google.com (mail-wm0-x22c.google.com. [2a00:1450:400c:c09::22c]) by mx.google.com with ESMTPS id js4si9898758wjc.164.2016.02.03.05.18.58 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 03 Feb 2016 05:18:58 -0800 (PST) Received: by mail-wm0-x22c.google.com with SMTP id l66so163260972wml.0 for ; Wed, 03 Feb 2016 05:18:58 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: From: Dmitry Vyukov Date: Wed, 3 Feb 2016 14:18:38 +0100 Message-ID: Subject: Re: mm: uninterruptable tasks hanged on mmap_sem Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Jiri Kosina Cc: Andrew Morton , "Kirill A. Shutemov" , Oleg Nesterov , Konstantin Khlebnikov , "linux-mm@kvack.org" , LKML , Takashi Iwai , syzkaller , Kostya Serebryany , Alexander Potapenko , Sasha Levin On Wed, Feb 3, 2016 at 2:11 PM, Jiri Kosina wrote: > On Tue, 2 Feb 2016, Dmitry Vyukov wrote: > >> Hello, >> >> If the following program run in a parallel loop, eventually it leaves >> hanged uninterruptable tasks on mmap_sem. >> >> [ 4074.740298] sysrq: SysRq : Show Locks Held >> [ 4074.740780] Showing all locks held in the system: >> ... >> [ 4074.762133] 1 lock held by a.out/1276: >> [ 4074.762427] #0: (&mm->mmap_sem){++++++}, at: [] >> __mm_populate+0x25c/0x350 >> [ 4074.763149] 1 lock held by a.out/1147: >> [ 4074.763438] #0: (&mm->mmap_sem){++++++}, at: [] >> vm_mmap_pgoff+0x12c/0x1b0 >> [ 4074.764164] 1 lock held by a.out/1284: >> [ 4074.764447] #0: (&mm->mmap_sem){++++++}, at: [] >> __mm_populate+0x25c/0x350 >> [ 4074.765287] > > I've now tried to reproduce this on 4.5-rc1 (with the lock_fdc() fix > applied), and I am not seeing any stuck tasks so far. > > Could you please provide more details about the reproduction scenario? > Namely, how many parallel invocations are you typically running (and how > many cores does the system in question have), and what is the typical time > that you need for the problem to appear? Qemu with 4 cores, 32 parallel processes, it took 20 seconds (2409 program executions) to hang 2 of them just now. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org