From: Peter Zijlstra <peterz@infradead.org>
To: Petr Mladek <pmladek@suse.com>
Cc: Jan Kara <jack@suse.cz>, Ross Zwisler <zwisler@gmail.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Calvin Owens <calvinowens@fb.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>, Andy Lutomirski <luto@kernel.org>,
Peter Hurley <peter@hurleysoftware.com>,
LKML <linux-kernel@vger.kernel.org>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [PATCHv7 6/8] printk: use printk_safe buffers in printk
Date: Wed, 1 Feb 2017 17:15:41 +0100 [thread overview]
Message-ID: <20170201161541.GU6515@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20170201153910.GL6620@pathway.suse.cz>
On Wed, Feb 01, 2017 at 04:39:10PM +0100, Petr Mladek wrote:
> I guess that you are talking about the introduction of
> #define SCHED_WARN_ON(x) WARN_ONCE(x, #x)
No, there's a lot of regular WARN/WARN_ON/etc.. usage in the scheduler.
That thing was just a convenience wapper to print the condition that
warned.
> It reduces the risk of the deadlock but some risk is still there.
> IMHO, it does not avoid the lockdep warning.
It doesn't reduce anything, nor did it ever try. I really don't care if
it occasionally deadlocks, as long as it mostly gets out.
> One solution would be to hide the occasional deadlock and disable
> lockdep in SCHED_WARN_ON():
>
> #define SCHED_WARN_ON(x) \
> ({ \
> int __ret_sched_warn_on; \
> lockdep_off(); \
> __ret_sched_warn_on = WARN_ONCE(x, #x); \
> lockdep_on(); \
> unlikely(__ret_sched_warn_on); \
> })
Like said, there's plenty of regular WARN/WARN_ON usage, so this will
not help much.
> Another solution would be to redirect it into the
> alternative buffer and let it printed later:
>
> #define SCHED_WARN_ON(x) WARN_ONCE(x, #x) \
> ({ \
> unsigned long __sched_warn_on_flags; \
> printk_safe_enter_irqsave(__sched_warn_on_flags); \
> __ret_sched_warn_on = WARN_ONCE(x, #x); \
> printk_safe_exit_irqrestore(__sched_warn_on_flags); \
> unlikely(__ret_sched_warn_on); \
> })
So my kernel doesn't yet have that abomination; that redirects it to a
buffer for later printing right? I hope that buffer is big enough to
hold a full WARN splat and the machine lives long enough to make it to
printing that crap.
next prev parent reply other threads:[~2017-02-01 16:15 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-27 14:16 [PATCHv7 0/8] printk: use printk_safe to handle printk() recursive calls Sergey Senozhatsky
2016-12-27 14:16 ` [PATCHv7 1/8] printk: use vprintk_func in vprintk() Sergey Senozhatsky
2016-12-27 14:16 ` [PATCHv7 2/8] printk: rename nmi.c and exported api Sergey Senozhatsky
2017-01-04 13:07 ` Petr Mladek
2017-02-01 15:48 ` Steven Rostedt
2017-02-01 15:50 ` Steven Rostedt
2017-02-23 7:50 ` Geert Uytterhoeven
2017-02-23 8:02 ` Sergey Senozhatsky
2017-02-23 9:23 ` Geert Uytterhoeven
2016-12-27 14:16 ` [PATCHv7 3/8] printk: introduce per-cpu safe_print seq buffer Sergey Senozhatsky
2017-01-04 13:31 ` Petr Mladek
2017-01-05 1:01 ` Sergey Senozhatsky
2017-02-01 15:52 ` Steven Rostedt
2016-12-27 14:16 ` [PATCHv7 4/8] printk: always use deferred printk when flush printk_safe lines Sergey Senozhatsky
2017-02-01 16:06 ` Steven Rostedt
2017-02-02 6:05 ` Sergey Senozhatsky
2017-02-02 15:37 ` Petr Mladek
2017-02-02 15:52 ` Petr Mladek
2017-02-03 2:04 ` Sergey Senozhatsky
2017-02-03 11:18 ` Petr Mladek
2017-02-06 1:48 ` Sergey Senozhatsky
2017-02-06 2:08 ` Sergey Senozhatsky
2017-02-06 12:16 ` Petr Mladek
2017-02-06 13:27 ` Steven Rostedt
2017-02-06 16:42 ` Sergey Senozhatsky
2017-02-06 16:55 ` Steven Rostedt
2016-12-27 14:16 ` [PATCHv7 5/8] printk: report lost messages in printk safe/nmi contexts Sergey Senozhatsky
2017-01-04 14:46 ` Petr Mladek
2017-01-05 1:01 ` Sergey Senozhatsky
2017-02-01 16:37 ` Steven Rostedt
2017-02-02 2:02 ` Sergey Senozhatsky
2017-02-02 14:34 ` Steven Rostedt
2017-02-02 16:13 ` Petr Mladek
2017-02-03 1:57 ` Sergey Senozhatsky
2017-02-03 3:13 ` Steven Rostedt
2016-12-27 14:16 ` [PATCHv7 6/8] printk: use printk_safe buffers in printk Sergey Senozhatsky
2017-01-31 17:27 ` Ross Zwisler
2017-02-01 9:06 ` Jan Kara
2017-02-01 9:37 ` Peter Zijlstra
2017-02-01 15:39 ` Petr Mladek
2017-02-01 16:15 ` Peter Zijlstra [this message]
2017-02-01 16:41 ` Steven Rostedt
2017-02-02 2:11 ` Sergey Senozhatsky
2017-02-02 9:07 ` Peter Zijlstra
2017-02-02 10:03 ` Sergey Senozhatsky
2017-02-02 15:20 ` Petr Mladek
2017-02-03 2:45 ` Sergey Senozhatsky
2017-02-02 1:59 ` Sergey Senozhatsky
2017-02-01 17:04 ` Steven Rostedt
2017-02-02 2:13 ` Sergey Senozhatsky
2016-12-27 14:16 ` [PATCHv7 7/8] printk: remove zap_locks() function Sergey Senozhatsky
2016-12-27 14:16 ` [PATCHv7 8/8] printk: convert the rest to printk-safe Sergey Senozhatsky
2017-01-04 16:28 ` Petr Mladek
2017-01-05 1:00 ` Sergey Senozhatsky
2017-01-05 16:58 ` [PATCHv7 0/8] printk: use printk_safe to handle printk() recursive calls Petr Mladek
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