From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>,
Daniel Wang <wonderfly@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
Jiri Slaby <jslaby@suse.com>, Peter Feiner <pfeiner@google.com>,
linux-serial@vger.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [RFC][PATCHv2 1/4] panic: avoid deadlocks in re-entrant console drivers
Date: Thu, 25 Oct 2018 18:05:39 +0900 [thread overview]
Message-ID: <20181025090539.GD20702@jagdpanzerIV> (raw)
In-Reply-To: <20181025082947.gznv5roj3zxzlw3t@pathway.suse.cz>
On (10/25/18 10:29), Petr Mladek wrote:
>
> Yes, klogd is not a big deal. I just think that the bust_spinlocks()
> ping-pong would just confuse the code.
I agree; that's why I put some comments there.
> It might be better to keep the spinlocks busted and make sure that we do
> not cause regressions by not calling bust_spinlocks(0).
Sure, I understand. One reason to keep bust_spinlocks(0) there was "invoke
arch-specific bust_spinlocks(0), which might do something that common
bust_spinlocks() wouldn't do". Without going into details if any arch actually
does anything "special" in bust_spinlocks(0). Another reason was - this patch
looks like a -stable material to me; especially given that we have panic()
deadlock reports now. So I wanted to have a one liner which will not change
things for arch-s that re-define bust_spinlocks() and, at the same time,
fix the deadlock. Other than that I'm all for keeping spinlocks busted all
the time and just doing:
---
#ifdef CONFIG_VT
unblank_screen();
#endif
console_unblank();
---
in panic().
BTW, speaking of s390 bust_spinlocks(). It seems that starting from 4.21
all arch-s will use common bust_spinlocks() [1].
[..]
> > Hmm, I don't think I've seen any reports because of this. From printk/console
> > POV the locks which are not taken under oops_in_progress are not released.
>
> Fair enough. Let's keep debug_locks_off() in panic().
Agreed.
[1] lkml.kernel.org/r/20181025081108.GB26561@osiris
-ss
next prev parent reply other threads:[~2018-10-25 9:05 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-16 5:04 [RFC][PATCHv2 0/4] less deadlock prone serial consoles Sergey Senozhatsky
2018-10-16 5:04 ` [RFC][PATCHv2 1/4] panic: avoid deadlocks in re-entrant console drivers Sergey Senozhatsky
2018-10-17 4:48 ` Sergey Senozhatsky
2018-10-23 11:07 ` Petr Mladek
2018-10-23 11:54 ` Sergey Senozhatsky
2018-10-23 12:04 ` Sergey Senozhatsky
2018-10-23 12:12 ` Sergey Senozhatsky
2018-10-25 9:06 ` Petr Mladek
2018-10-25 9:31 ` Sergey Senozhatsky
2018-10-25 8:29 ` Petr Mladek
2018-10-25 9:05 ` Sergey Senozhatsky [this message]
2018-10-25 10:10 ` [PATCHv3] " Sergey Senozhatsky
2018-10-25 10:51 ` kbuild test robot
2018-10-25 11:56 ` Sergey Senozhatsky
2018-10-31 12:27 ` Petr Mladek
2018-11-01 1:48 ` Sergey Senozhatsky
2018-11-01 8:08 ` Petr Mladek
2018-11-22 13:12 ` Petr Mladek
2018-12-12 0:53 ` Daniel Wang
2018-12-12 5:23 ` Sergey Senozhatsky
2018-12-12 5:59 ` Daniel Wang
2018-12-12 6:06 ` Sergey Senozhatsky
2018-12-12 6:09 ` Daniel Wang
2018-10-16 5:04 ` [RFC][PATCHv2 2/4] printk: move printk_safe macros to printk header Sergey Senozhatsky
2018-10-16 7:27 ` Peter Zijlstra
2018-10-16 11:40 ` Petr Mladek
2018-10-16 12:17 ` Peter Zijlstra
2018-10-17 10:50 ` Petr Mladek
2018-10-17 14:00 ` Peter Zijlstra
2018-10-22 14:30 ` Petr Mladek
2018-10-16 12:27 ` Sergey Senozhatsky
2018-10-16 12:38 ` Peter Zijlstra
2018-10-16 12:54 ` Peter Zijlstra
2018-10-16 14:21 ` Peter Zijlstra
2018-10-17 4:32 ` Sergey Senozhatsky
2018-10-17 7:57 ` Peter Zijlstra
2018-10-17 13:36 ` Sergey Senozhatsky
2018-10-23 6:25 ` Sergey Senozhatsky
2018-10-16 5:04 ` [RFC][PATCHv2 3/4] serial: introduce uart_port locking helpers Sergey Senozhatsky
2018-12-08 3:12 ` Sergey Senozhatsky
2018-12-12 11:08 ` Greg Kroah-Hartman
2018-10-16 5:04 ` [RFC][PATCHv2 4/4] tty: 8250: switch to " Sergey Senozhatsky
2018-10-16 7:23 ` [RFC][PATCHv2 0/4] less deadlock prone serial consoles Peter Zijlstra
2018-10-16 8:12 ` Sergey Senozhatsky
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