BUG: using smp_processor_id() in preemptible [00000000] during put_task_stack

Path	csiph.com!goblin3!goblin2!goblin.stu.neva.ru!news.unit0.net!news.panservice.it!bofh.it!news.nic.it!robomod
From	Michal Hocko <mhocko@kernel.org>
Newsgroups	linux.kernel
Subject	BUG: using smp_processor_id() in preemptible [00000000] during put_task_stack
Date	Fri, 09 Dec 2016 15:30:02 +0100
Message-ID	<sMuls-4n9-49@gated-at.bofh.it> (permalink)
X-Original-To	Andy Lutomirski <luto@amacapital.net>
X-Google-Dkim-Signature	v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:subject:message-id:mime-version :content-disposition:user-agent; bh=sGsAMg9AlilxxIO5d+PZ+a6zSu3wI+zlNXLov5Eixqc=; b=P2OjRcZ3Lx8q5EakpKaiUCLl52pW3AnzAptGFirunr7SQcfrlKBJKa2UlpoEzKv68k g4tbeVgpqxsub1YQBuimDwqbwSgjyT9SRcZFpqY9nFJ/oPqvRvJaciLOECM18OnX7uj0 jCrYyMSm9JXJgt22JADoMVeClJwMLQDVl3ANo9GL7xDR4NoiBgU5H/XfqC0qJIoiUphj 0WyDXj/jz1CoeQjDDw7K2mSLHqJWd5ALaFkQ1Py9d1A2V0jRv3O4cZKVT4iI288VZgAm g5E7Y1XgEna7uUIDutbmK48pjo3eTfcyy92gvEmNmxDKHTV85glolirBaSv7EZsieC4D 1Ppw==
X-Gm-Message-State	AKaTC02ShpNKWPTtH6/+YAsWSng074llbqfzt3g3jDa0VC6lyNlmCH+OVCrtfZ8y/OXPCw==
X-Received	by 10.194.86.165 with SMTP id q5mr67883966wjz.178.1481293702517; Fri, 09 Dec 2016 06:28:22 -0800 (PST)
MIME-Version	1.0
Content-Type	text/plain; charset=us-ascii
Content-Disposition	inline
User-Agent	Mutt/1.6.0 (2016-04-01)
Sender	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	51
Organization	linux.* mail to news gateway
X-Original-Cc	LKML <linux-kernel@vger.kernel.org>
X-Original-Date	Fri, 9 Dec 2016 15:28:20 +0100
X-Original-Message-ID	<20161209142820.GA4334@dhcp22.suse.cz>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1539404

Show key headers only | View raw

Hi Andy,
I am hitting the following
[  570.715345] BUG: using smp_processor_id() in preemptible [00000000] code: umount/6193
[  570.716880] caller is debug_smp_processor_id+0x17/0x19
[  570.717876] CPU: 2 PID: 6193 Comm: umount Tainted: G        W       4.9.0-rc8-nofstest4-next-20161209-00012-g0db618dfb2cf #1017
[  570.720162] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.3-20161025_171302-gandalf 04/01/2014
[  570.720862] Call Trace:
[  570.720862]  dump_stack+0x68/0x92
[  570.720862]  check_preemption_disabled+0xce/0xe0
[  570.720862]  debug_smp_processor_id+0x17/0x19
[  570.720862]  vfree_atomic+0x2f/0x65
[  570.720862]  put_task_stack+0xd0/0x13c
[  570.720862]  kthread_stop+0x108/0x29a
[  570.720862]  destroy_workqueue+0x167/0x1fb
[  570.720862]  ext4_put_super+0x44/0x2fa
[  570.720862]  generic_shutdown_super+0x6a/0xeb
[  570.720862]  kill_block_super+0x27/0x67
[  570.720862]  deactivate_locked_super+0x30/0x68
[  570.720862]  deactivate_super+0x3e/0x41
[  570.720862]  cleanup_mnt+0x58/0x76
[  570.720862]  __cleanup_mnt+0x12/0x14
[  570.720862]  task_work_run+0x77/0xa0
[  570.720862]  exit_to_usermode_loop+0x67/0x92
[  570.720862]  do_syscall_64+0x16c/0x197
[  570.720862]  entry_SYSCALL64_slow_path+0x25/0x25

it seems that vfre_atomic doesn't like it has preemption enabled in
__vfree_deferred which calls this_cpu_ptr. I haven't studied the code
deeply but I guess what we want is to put vfree_atomic into the atomic
context. Something like the following or at least disable preemption
around vfree_atomic. Or maybe I am completely missing what the above
warning tries to tell...

diff --git a/kernel/fork.c b/kernel/fork.c
index 8f63bf912195..1c69561eec55 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -227,9 +227,9 @@ static inline void free_thread_stack(struct task_struct *tsk)
 			local_irq_restore(flags);
 			return;
 		}
+		vfree_atomic(tsk->stack);
 		local_irq_restore(flags);
 
-		vfree_atomic(tsk->stack);
 		return;
 	}
 #endif
-- 
Michal Hocko
SUSE Labs

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

BUG: using smp_processor_id() in preemptible [00000000] during  put_task_stack Michal Hocko <mhocko@kernel.org> - 2016-12-09 15:30 +0100

csiph-web