From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Byungchul Park <byungchul.park@lge.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
akpm@linux-foundation.org, mingo@kernel.org,
linux-kernel@vger.kernel.org, akinobu.mita@gmail.com,
jack@suse.cz, peter@hurleysoftware.com, tglx@linutronix.de,
peterz@infradead.org, rostedt@goodmis.org
Subject: Re: [PATCH v6 2/2] printk: Make printing of spin_dump() deferred to avoid a deadlock
Date: Mon, 14 Mar 2016 11:40:55 +0900 [thread overview]
Message-ID: <20160314024054.GC8074@swordfish> (raw)
In-Reply-To: <20160314023030.GE5220@X58A-UD3R>
Hi,
On (03/14/16 11:30), Byungchul Park wrote:
[..]
> > so can it be
> >
> > vprintk_emit()
> > __spin_dump_deferred()
> > vprintk_deferred()
> > vprintk_emit()
> > __spin_dump_deferred()
> ^^^
> can be caused by raw_spin_lock(logbug_lock)
>
> > vprintk_deferred()
>
> Yes, it can happen by raw_spin_lock(logbuf_lock) to print warning or error
> message. Are you worrying about an infinite recursion?
yes.
> 1. In the case printing warning, eventually it can fill the buffer without
> actual printing using console.
so the worry is that the CPU that spins on __spin_dump_deferred() has IRQs
disabled and `printk_pending' bit set; but IRQ may never be enabled on this
CPU.
> 2. In the case printing error, the infinite recursion can be prevented by
> debug_locks_off().
>
> Therefore, no problem.
-ss
next prev parent reply other threads:[~2016-03-14 2:39 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-11 10:37 [PATCH v6 0/2] Make printing of spin_dump() deferred to avoid a deadlock Byungchul Park
2016-03-11 10:37 ` [PATCH v6 1/2] printk: Factor out buffering and irq work queuing in printk_deferred Byungchul Park
2016-03-14 1:21 ` Sergey Senozhatsky
2016-03-14 4:45 ` Byungchul Park
2016-03-11 10:37 ` [PATCH v6 2/2] printk: Make printing of spin_dump() deferred to avoid a deadlock Byungchul Park
2016-03-14 1:37 ` Sergey Senozhatsky
2016-03-14 2:30 ` Byungchul Park
2016-03-14 2:40 ` Sergey Senozhatsky [this message]
2016-03-14 4:17 ` Byungchul Park
2016-03-16 2:06 ` Byungchul Park
2016-03-18 5:55 ` [PATCH] lib/spinlock_debug: Prevent a unnecessary recursive spin_dump() Byungchul Park
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