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From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Byungchul Park <byungchul.park@lge.com>
Cc: akpm@linux-foundation.org, mingo@kernel.org,
	linux-kernel@vger.kernel.org, akinobu.mita@gmail.com,
	jack@suse.cz, sergey.senozhatsky.work@gmail.com,
	peter@hurleysoftware.com, torvalds@linux-foundation.org
Subject: Re: [PATCH v5] lib/spinlock_debug.c: prevent a recursive cycle in the debug code
Date: Sun, 31 Jan 2016 21:40:08 +0900	[thread overview]
Message-ID: <20160131124007.GB1306@swordfish> (raw)
In-Reply-To: <20160129125457.GI31266@X58A-UD3R>

On (01/29/16 21:54), Byungchul Park wrote:
> Hello, Andrew
> 
> Please take this v5 patch instead of v2 patch, which you took. Or give your
> opinion.
> 
> > It causes an infinite recursive cycle when using CONFIG_DEBUG_SPINLOCK,
> > in the spin_dump(). Backtrace prints printk() -> console_trylock() ->
> > do_raw_spin_lock() -> spin_dump() -> printk()... infinitely.
> > 
> > When the spin_dump() is called from printk(), we should prevent the
> > debug spinlock code from calling printk() again in that context. It's
> > reasonable to avoid printing "lockup suspected" which is just a warning
> > message but it would cause a real lockup definitely.


Hello Byungchul,

thanks for the patch and thanks for bringing this topic to discussion.
let's not rush, if you don't mind, and return back for a bit. there are
some serious cases (when we really would want to see a spin_dump output)
that are broken.

	-ss

  reply	other threads:[~2016-01-31 12:38 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-29 12:43 [PATCH v5] lib/spinlock_debug.c: prevent a recursive cycle in the debug code Byungchul Park
2016-01-29 12:54 ` Byungchul Park
2016-01-31 12:40   ` Sergey Senozhatsky [this message]
2016-02-01  1:45     ` Byungchul Park
2016-02-01  2:13       ` Sergey Senozhatsky
2016-01-30  9:27 ` Ingo Molnar
2016-02-02  2:34   ` Byungchul Park
2016-02-01  2:31 ` Sergey Senozhatsky
2016-02-01  6:28   ` Byungchul Park

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