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From: Petr Mladek <pmladek@suse.com>
To: Daniel Wang <wonderfly@google.com>
Cc: rostedt@goodmis.org, stable@vger.kernel.org,
	Alexander.Levin@microsoft.com, akpm@linux-foundation.org,
	byungchul.park@lge.com, dave.hansen@intel.com,
	hannes@cmpxchg.org, jack@suse.cz, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, mathieu.desnoyers@efficios.com,
	mgorman@suse.de, mhocko@kernel.org, pavel@ucw.cz,
	penguin-kernel@i-love.sakura.ne.jp, peterz@infradead.org,
	tj@kernel.org, torvalds@linux-foundation.org, vbabka@suse.cz,
	xiyou.wangcong@gmail.com, Peter Feiner <pfeiner@google.com>
Subject: Re: 4.14 backport request for dbdda842fe96f: "printk: Add console owner and waiter logic to load balance console writes"
Date: Tue, 2 Oct 2018 10:42:25 +0200	[thread overview]
Message-ID: <20181002084225.6z2b74qem3mywukx@pathway.suse.cz> (raw)
In-Reply-To: <CAJmjG29Jwn_1E5zexcm8eXTG=cTWyEr1gjSfSAS2fueB_V0tfg@mail.gmail.com>

On Mon 2018-10-01 13:37:30, Daniel Wang wrote:
> On Mon, Oct 1, 2018 at 12:23 PM Steven Rostedt <rostedt@goodmis.org> wrote:
> >
> > > Serial console logs leading up to the deadlock. As can be seen the stack trace
> > > was incomplete because the printing path hit a timeout.
> >
> > I'm fine with having this backported.
> 
> Thanks. I can send the cherrypicks your way. Do you recommend that I
> include the three follow-up fixes though?
> 
> c14376de3a1b printk: Wake klogd when passing console_lock owner
> fd5f7cde1b85 printk: Never set console_may_schedule in console_trylock()
> c162d5b4338d printk: Hide console waiter logic into helpers
> dbdda842fe96 printk: Add console owner and waiter logic to load
> balance console writes

This list looks complete and I am fine with backporting it to 4.14.

Well, I still wonder why it helped and why you do not see it with 4.4.
I have a feeling that the console owner switch helped only by chance.
In fact, you might be affected by a race in
printk_safe_flush_on_panic() that was fixed by the commit:

554755be08fba31c7 printk: drop in_nmi check from printk_safe_flush_on_panic()

The above one commit might be enough. Well, there was one more
NMI-related race that was fixed by:

ba552399954dde1b printk: Split the code for storing a message into the log buffer
a338f84dc196f44b printk: Create helper function to queue deferred console handling
03fc7f9c99c1e7ae printk/nmi: Prevent deadlock when accessing the main log buffer in NMI

Best Regards,
Petr

  parent reply	other threads:[~2018-10-02  8:42 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-27 19:46 4.14 backport request for dbdda842fe96f: "printk: Add console owner and waiter logic to load balance console writes" Daniel Wang
2018-10-01 19:23 ` Steven Rostedt
2018-10-01 20:13   ` Pavel Machek
2018-10-01 20:21     ` Vlastimil Babka
2018-10-01 20:38       ` Daniel Wang
2018-10-01 20:29     ` Steven Rostedt
2018-10-01 20:37   ` Daniel Wang
2018-10-01 20:40     ` Sasha Levin
2018-10-01 20:40       ` Sasha Levin
2018-10-02  8:42     ` Petr Mladek [this message]
2018-10-02 17:21       ` Daniel Wang
2018-10-03  0:15       ` Daniel Wang
2018-10-03  1:23         ` Steven Rostedt
2018-10-03  9:14           ` Petr Mladek
2018-10-03 17:16             ` Daniel Wang
2018-10-03 17:37               ` Steven Rostedt
2018-10-03 18:37                 ` Daniel Wang
2018-10-03 23:37                   ` Daniel Wang
2018-10-04  7:44                   ` Sergey Senozhatsky
2018-10-04  8:05                     ` Sergey Senozhatsky
2018-10-04  8:36                     ` Petr Mladek
2018-10-04  8:55                       ` Sergey Senozhatsky
2018-10-04  8:55                         ` Sergey Senozhatsky
2018-10-21 18:09                         ` Daniel Wang
2018-10-22  9:32                           ` Petr Mladek
2018-10-22 10:09                           ` Sergey Senozhatsky
2018-11-01 16:05                             ` Daniel Wang
2018-11-09  6:47                               ` Sergey Senozhatsky
2018-12-12  1:16                                 ` Daniel Wang
2018-12-12  5:21                                   ` Sergey Senozhatsky
2018-12-12  6:08                                     ` Daniel Wang
2018-12-12  6:28                                       ` Sergey Senozhatsky
2018-12-12  6:48                                         ` Sasha Levin
2018-12-12  8:10                                           ` Sergey Senozhatsky
2018-12-12 13:36                                             ` Petr Mladek
2018-12-12 13:59                                               ` Sergey Senozhatsky
2018-12-12 17:43                                                 ` Sasha Levin
2018-12-12 20:11                                                   ` Daniel Wang
2018-12-12 21:43                                                     ` Sasha Levin
2018-12-12 21:49                                                       ` Daniel Wang
2018-12-12 21:52                                                         ` Sasha Levin
2018-12-12 21:56                                                           ` Daniel Wang
2018-12-13  0:40                                                             ` Daniel Wang
2018-12-13  2:27                                                               ` Sergey Senozhatsky
2018-12-13  2:39                                                                 ` Daniel Wang
2018-12-13  9:59                                                                   ` Petr Mladek
2018-12-13 14:29                                                                     ` Sasha Levin
2018-12-13  2:07                                                           ` Sergey Senozhatsky
2018-12-28  0:16                                             ` Sergey Senozhatsky
2018-12-28  8:27                                               ` Greg KH
2018-12-28 22:03                                                 ` Daniel Wang
2018-12-28 22:03                                                   ` Daniel Wang
2018-12-30  3:03                                                   ` Sergey Senozhatsky
2018-10-04  7:49                 ` Petr Mladek
2018-10-02  8:16 ` Sergey Senozhatsky

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