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From: Qian Cai <cai@lca.pw>
To: Michal Hocko <mhocko@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	sergey.senozhatsky.work@gmail.com, rostedt@goodmis.org,
	peterz@infradead.org, linux-mm@kvack.org,
	john.ogness@linutronix.de, akpm@linux-foundation.org,
	Vasily Gorbik <gor@linux.ibm.com>,
	Peter Oberparleiter <oberpar@linux.ibm.com>,
	david@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk()
Date: Wed, 09 Oct 2019 09:43:13 -0400	[thread overview]
Message-ID: <1570628593.5937.3.camel@lca.pw> (raw)
In-Reply-To: <20191009132746.GA6681@dhcp22.suse.cz>

On Wed, 2019-10-09 at 15:27 +0200, Michal Hocko wrote:
> On Wed 09-10-19 09:06:42, Qian Cai wrote:
> [...]
> > https://lore.kernel.org/linux-mm/1570460350.5576.290.camel@lca.pw/
> > 
> > [  297.425964] -> #1 (&port_lock_key){-.-.}:
> > [  297.425967]        __lock_acquire+0x5b3/0xb40
> > [  297.425967]        lock_acquire+0x126/0x280
> > [  297.425968]        _raw_spin_lock_irqsave+0x3a/0x50
> > [  297.425969]        serial8250_console_write+0x3e4/0x450
> > [  297.425970]        univ8250_console_write+0x4b/0x60
> > [  297.425970]        console_unlock+0x501/0x750
> > [  297.425971]        vprintk_emit+0x10d/0x340
> > [  297.425972]        vprintk_default+0x1f/0x30
> > [  297.425972]        vprintk_func+0x44/0xd4
> > [  297.425973]        printk+0x9f/0xc5
> > [  297.425974]        register_console+0x39c/0x520
> > [  297.425975]        univ8250_console_init+0x23/0x2d
> > [  297.425975]        console_init+0x338/0x4cd
> > [  297.425976]        start_kernel+0x534/0x724
> > [  297.425977]        x86_64_start_reservations+0x24/0x26
> > [  297.425977]        x86_64_start_kernel+0xf4/0xfb
> > [  297.425978]        secondary_startup_64+0xb6/0xc0
> > 
> > where the report again show the early boot call trace for the locking
> > dependency,
> > 
> > console_owner --> port_lock_key
> > 
> > but that dependency clearly not only happen in the early boot.
> 
> Can you provide an example of the runtime dependency without any early
> boot artifacts? Because this discussion really doens't make much sense
> without a clear example of a _real_ lockdep report that is not a false
> possitive. All of them so far have been concluded to be false possitive
> AFAIU.

An obvious one is in the above link. Just replace the trace in #1 above with
printk() from anywhere, i.e., just ignore the early boot calls there as they are
 not important.

printk()
  console_unlock()
    console_lock_spinning_enable() --> console_owner_lock
  call_console_drivers()
    serial8250_console_write() --> port->lock

  reply	other threads:[~2019-10-09 13:43 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-04 22:26 [PATCH v2] mm/page_isolation: fix a deadlock with printk() Qian Cai
2019-10-07  8:07 ` Michal Hocko
2019-10-07  9:05   ` Petr Mladek
2019-10-07 11:33     ` Michal Hocko
2019-10-07 12:34     ` Qian Cai
     [not found]   ` <FB72D947-A0F9-43E7-80D9-D7ACE33849C7@lca.pw>
2019-10-07 11:37     ` Michal Hocko
2019-10-07 12:11       ` Qian Cai
2019-10-07 12:43         ` Michal Hocko
2019-10-07 13:07           ` Qian Cai
2019-10-07 14:10             ` Petr Mladek
2019-10-07 14:30 ` Petr Mladek
2019-10-07 14:49   ` Michal Hocko
2019-10-08  7:43     ` Petr Mladek
2019-10-08  8:27       ` Michal Hocko
2019-10-08 12:56         ` Christian Borntraeger
2019-10-08 16:08           ` Qian Cai
2019-10-08 18:35             ` Michal Hocko
2019-10-08 19:06               ` Qian Cai
2019-10-08 19:17                 ` Michal Hocko
2019-10-08 19:35                   ` Qian Cai
2019-10-09 11:49                     ` Petr Mladek
2019-10-09 13:06                       ` Qian Cai
2019-10-09 13:27                         ` Michal Hocko
2019-10-09 13:43                           ` Qian Cai [this message]
2019-10-09 13:51                             ` Michal Hocko
2019-10-09 14:19                               ` Qian Cai
2019-10-09 14:34                                 ` Michal Hocko
2019-10-09 15:08                                   ` Qian Cai
2019-10-09 16:23                                     ` Michal Hocko
2019-10-10  9:01                                       ` Qian Cai
2019-10-10 10:59                                         ` Michal Hocko
2019-10-10 13:11                                           ` Qian Cai
2019-10-10 14:18                                             ` Michal Hocko
2019-10-10 14:47                                               ` Qian Cai
2019-10-10 17:30                                                 ` Michal Hocko
2019-10-10 17:48                                                   ` Qian Cai
2019-10-10 18:06                                                     ` Michal Hocko
2019-10-10 18:59                                                       ` David Hildenbrand
2019-10-09 14:24                             ` Petr Mladek
2019-10-09 14:46                               ` Qian Cai
2019-10-10  7:57                                 ` Petr Mladek
2019-10-09 11:39                 ` Petr Mladek
2019-10-09 13:56             ` Peter Oberparleiter
2019-10-09 14:26               ` Michal Hocko
2019-10-10  5:12                 ` Sergey Senozhatsky
2019-10-10  7:40                   ` Michal Hocko
2019-10-10  8:16                     ` Sergey Senozhatsky
2019-10-10  8:37                       ` Michal Hocko
2019-10-10  8:21                   ` Petr Mladek
2019-10-10  8:39                     ` Sergey Senozhatsky
2019-10-10 11:11                       ` Petr Mladek
2019-10-09 15:25               ` Qian Cai
2019-10-07 14:59   ` Qian Cai
2019-10-07 15:12     ` Michal Hocko
2019-10-07 15:33       ` Qian Cai
2019-10-08  8:15         ` Petr Mladek
2019-10-08  9:32           ` Qian Cai
2019-10-08 13:13           ` Steven Rostedt
2019-10-08 13:23             ` Qian Cai
2019-10-08 13:33               ` Steven Rostedt
2019-10-08 13:42               ` Petr Mladek
2019-10-08 13:48                 ` Michal Hocko
2019-10-08 14:03                 ` Qian Cai
2019-10-08 14:08                   ` Michal Hocko
2019-10-08  8:40         ` Michal Hocko
2019-10-08 10:04           ` Qian Cai
2019-10-08 10:39             ` Michal Hocko
2019-10-08 12:00               ` Qian Cai
2019-10-08 12:39                 ` Michal Hocko
2019-10-08 13:06                   ` Qian Cai
2019-10-08 13:37                     ` Michal Hocko
2019-10-08 13:08     ` Petr Mladek
2019-10-08 13:33       ` Qian Cai

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