From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 321476B0343 for ; Fri, 24 Mar 2017 08:21:43 -0400 (EDT) Received: by mail-pg0-f71.google.com with SMTP id x125so1112870pgb.5 for ; Fri, 24 Mar 2017 05:21:43 -0700 (PDT) Received: from EUR03-DB5-obe.outbound.protection.outlook.com (mail-eopbgr40128.outbound.protection.outlook.com. [40.107.4.128]) by mx.google.com with ESMTPS id t3si1904848pfb.18.2017.03.24.05.21.40 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 24 Mar 2017 05:21:41 -0700 (PDT) Subject: Re: [PATCH] mm: Remove pointless might_sleep() in remove_vm_area(). References: <1490352808-7187-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> From: Andrey Ryabinin Message-ID: <59149d48-2a8e-d7c0-8009-1d0b3ea8290b@virtuozzo.com> Date: Fri, 24 Mar 2017 15:22:57 +0300 MIME-Version: 1.0 In-Reply-To: <1490352808-7187-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa , linux-mm@kvack.org Cc: Matthew Wilcox , Christoph Hellwig , Jisheng Zhang , Joel Fernandes , Chris Wilson , John Dias , Thomas Gleixner , "H. Peter Anvin" , Ingo Molnar On 03/24/2017 01:53 PM, Tetsuo Handa wrote: > Commit 5803ed292e63a1bf ("mm: mark all calls into the vmalloc subsystem > as potentially sleeping") added might_sleep() to remove_vm_area() from > vfree(), and is causing > > [ 2.616064] BUG: sleeping function called from invalid context at mm/vmalloc.c:1480 > [ 2.616125] in_atomic(): 1, irqs_disabled(): 0, pid: 341, name: plymouthd > [ 2.616156] 2 locks held by plymouthd/341: > [ 2.616158] #0: (drm_global_mutex){+.+.+.}, at: [] drm_release+0x3b/0x3b0 [drm] > [ 2.616256] #1: (&(&tfile->lock)->rlock){+.+...}, at: [] ttm_object_file_release+0x28/0x90 [ttm] > [ 2.616270] CPU: 2 PID: 341 Comm: plymouthd Not tainted 4.11.0-0.rc3.git0.1.kmallocwd.fc25.x86_64+debug #1 > [ 2.616271] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 07/02/2015 > [ 2.616273] Call Trace: > [ 2.616281] dump_stack+0x86/0xc3 > [ 2.616285] ___might_sleep+0x17d/0x250 > [ 2.616289] __might_sleep+0x4a/0x80 > [ 2.616293] remove_vm_area+0x22/0x90 > [ 2.616296] __vunmap+0x2e/0x110 > [ 2.616299] vfree+0x42/0x90 > [ 2.616304] kvfree+0x2c/0x40 > [ 2.616312] drm_ht_remove+0x1a/0x30 [drm] > [ 2.616317] ttm_object_file_release+0x50/0x90 [ttm] > [ 2.616324] vmw_postclose+0x47/0x60 [vmwgfx] > [ 2.616331] drm_release+0x290/0x3b0 [drm] > [ 2.616338] __fput+0xf8/0x210 > [ 2.616342] ____fput+0xe/0x10 > [ 2.616345] task_work_run+0x85/0xc0 > [ 2.616351] exit_to_usermode_loop+0xb4/0xc0 > [ 2.616355] do_syscall_64+0x185/0x1f0 > [ 2.616359] entry_SYSCALL64_slow_path+0x25/0x25 > > warning. > > But commit f9e09977671b618a ("mm: turn vmap_purge_lock into a mutex") did > not make vfree() potentially sleeping because try_purge_vmap_area_lazy() > is still using mutex_trylock(). Thus, this is a false positive warning. > Commit f9e09977671b618a did not made vfree() sleeping. Commit 763b218ddfa "mm: add preempt points into __purge_vmap_area_lazy()" did this, thus it's not a false positive. > ___might_sleep() via cond_resched_lock() in __purge_vmap_area_lazy() from > try_purge_vmap_area_lazy() from free_vmap_area_noflush() from > free_unmap_vmap_area() from remove_vm_area() which might trigger same > false positive warning is remaining. But so far we haven't heard about > warning from that path. And why that would be a false positive? -- 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