From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Petr Mladek <pmladek@suse.com>,
linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [PATCH] kernel/printk: prevent deadlock at calling kmsg_dump from NMI context
Date: Sat, 13 Jul 2019 15:09:29 +0900 [thread overview]
Message-ID: <20190713060929.GB1038@tigerII.localdomain> (raw)
In-Reply-To: <156294329676.1745.2620297516210526183.stgit@buzz>
On (07/12/19 17:54), Konstantin Khlebnikov wrote:
> Function kmsg_dump could be invoked from NMI context intentionally or
> accidentally because it is called at various oops/panic paths.
> Kernel message dumpers are not ready to work in NMI context right now.
> They could deadlock on lockbuf_lock or break internal structures.
Hmm.
printk()-s from NMI go through per-CPU printk_safe/nmi - a bunch of
lockless buffers which is supposed to deal with printk() deadlocks,
including NMI printk()-s.
include/linux/hardirq.h
#define nmi_enter()
...
printk_nmi_enter();
...
#define nmi_exit()
...
printk_nmi_exit();
...
So we are not really supposed to deadlock.
-ss
next prev parent reply other threads:[~2019-07-13 6:09 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-12 14:54 Konstantin Khlebnikov
2019-07-13 6:09 ` Sergey Senozhatsky [this message]
2019-07-13 6:46 ` Konstantin Khlebnikov
2019-07-13 13:19 ` Sergey Senozhatsky
2019-07-13 14:03 ` Konstantin Khlebnikov
2019-07-15 2:33 ` Sergey Senozhatsky
2019-07-15 7:38 ` Konstantin Khlebnikov
2019-07-15 7:54 ` Sergey Senozhatsky
2019-07-15 7:54 ` Petr Mladek
2019-07-15 8:12 ` Konstantin Khlebnikov
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