From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: 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>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [RFC][PATCHv2 1/4] panic: avoid deadlocks in re-entrant console drivers
Date: Tue, 23 Oct 2018 21:12:30 +0900 [thread overview]
Message-ID: <20181023121057.GC10251@jagdpanzerIV> (raw)
In-Reply-To: <20181023120441.GB10251@jagdpanzerIV>
On (10/23/18 21:04), Sergey Senozhatsky wrote:
>
> Seems that s390 is the only arch which defines its own bust_spinlocks().
> Not sure why... Just to play games with console_loglevel?
>
> ---
>
> void bust_spinlocks(int yes)
> {
> if (yes) {
> oops_in_progress = 1;
> } else {
> int loglevel_save = console_loglevel;
> console_unblank();
> oops_in_progress = 0;
> /*
> * OK, the message is on the console. Now we call printk()
> * without oops_in_progress set so that printk will give klogd
> * a poke. Hold onto your hats...
> */
> console_loglevel = 15;
> printk(" ");
> console_loglevel = loglevel_save;
> }
> }
>
> ---
>
> The "printk(" "); without oops_in_progress" part is a bit worrisome.
> This thing technically can deadlock. Unless s390 has no NMI panic().
And console_unblank() is not guaranteed to print anything (unlike
console_flush_on_panic(), but oops is not panic() yet, so we can't
replace it with flush_on_panic()) - console_sem can be locked, so
console_unblank() would do nothing.
That printk(" ") probably wants to be printk_deferred(" ").
-ss
next prev parent reply other threads:[~2018-10-23 12:12 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 [this message]
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
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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