From: Jiri Slaby <jslaby@suse.cz>
To: Dmitry Vyukov <dvyukov@google.com>,
paulkf@microgate.com, LKML <linux-kernel@vger.kernel.org>
Cc: Eric Dumazet <edumazet@google.com>,
Alexander Potapenko <glider@google.com>,
Kostya Serebryany <kcc@google.com>,
syzkaller <syzkaller@googlegroups.com>,
Sasha Levin <sasha.levin@oracle.com>
Subject: Re: Deadlock in n_hdlc_buf_put
Date: Thu, 26 Nov 2015 19:17:46 +0100 [thread overview]
Message-ID: <56574CCA.8010807@suse.cz> (raw)
In-Reply-To: <CACT4Y+bRrmT8PepDU0WZsYwksULJrdJKSTsMWRDXojFsf=GwBg@mail.gmail.com>
On 11/26/2015, 01:37 PM, Dmitry Vyukov wrote:
> [ 341.376188] =============================================
> [ 341.376607] [ INFO: possible recursive locking detected ]
> [ 341.376607] 4.4.0-rc1+ #117 Not tainted
> [ 341.376607] ---------------------------------------------
> [ 341.376607] syzkaller_execu/14066 is trying to acquire lock:
> [ 341.376607] (&(&list->spinlock)->rlock){......}, at:
> [<ffffffff82a9f548>] n_hdlc_buf_put+0x28/0x170
> [ 341.376607]
> [ 341.376607] but task is already holding lock:
> [ 341.376607] (&(&list->spinlock)->rlock){......}, at:
> [<ffffffff82aa1368>] n_hdlc_tty_ioctl+0x2b8/0x3f0
> [ 341.376607]
> [ 341.376607] other info that might help us debug this:
> [ 341.376607] Possible unsafe locking scenario:
> [ 341.376607]
> [ 341.376607] CPU0
> [ 341.376607] ----
> [ 341.376607] lock(&(&list->spinlock)->rlock);
> [ 341.376607] lock(&(&list->spinlock)->rlock);
Hi,
this is a lockdep false positive. The first one is tx_buf_list.spinlock,
the latter tx_free_buf_list.spinlock, both in flush_tx_queue. So we need
a lockdep annotation here.
thanks,
--
js
suse labs
next prev parent reply other threads:[~2015-11-26 18:17 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-26 12:37 Deadlock in n_hdlc_buf_put Dmitry Vyukov
2015-11-26 18:17 ` Jiri Slaby [this message]
2015-11-26 18:28 ` [PATCH] TTY: n_hdlc, fix lockdep false positive Jiri Slaby
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