From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Jan Kara <jack@suse.cz>, Tejun Heo <tj@kernel.org>,
Calvin Owens <calvinowens@fb.com>,
Thomas Gleixner <tglx@linutronix.de>,
Mel Gorman <mgorman@techsingularity.net>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Laura Abbott <labbott@redhat.com>,
Andy Lutomirski <luto@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Kees Cook <keescook@chromium.org>,
linux-kernel@vger.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [RFC][PATCHv4 5/6] printk: use printk_safe buffers
Date: Thu, 1 Dec 2016 11:14:07 +0900 [thread overview]
Message-ID: <20161201021407.GF12039@jagdpanzerIV> (raw)
In-Reply-To: <20161125142855.GI24103@pathway.suse.cz>
On (11/25/16 15:28), Petr Mladek wrote:
[..]
> I really like this patch. The only small problem is that it enables
> lockdep and it does not explain why it is safe. The change itself
> looks fine but it took me some time to prove why. IMHO, it is
> worth a comment.
>
> One thing is printk() recursion caused by lockdep warning
> triggered from inside vprintk_emit(). It is safe because
> the critical sections are guarded by printk_safe_enter()/exit()
> now.
>
> Another thing is lockdep recursion caused by catching another lockdep
> issue when printing warning about the first one. This is safe
> because lockdep protects itself. First, it sets and checks
> current->lockdep_recursion around the critical sections.
> Second, further checks are disabled entirely once first
> lockdep issue is found.
>
> If you add some comments about lockdep, feel free to use:
ok, I'll try to.
-ss
next prev parent reply other threads:[~2016-12-01 2:14 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-27 15:49 [RFC][PATCHv4 0/6] printk: use printk_safe to handle printk() recursive calls Sergey Senozhatsky
2016-10-27 15:49 ` [RFC][PATCHv4 1/6] printk: use vprintk_func in vprintk() Sergey Senozhatsky
2016-11-24 16:28 ` Petr Mladek
2016-10-27 15:49 ` [RFC][PATCHv4 2/6] printk: rename nmi.c and exported api Sergey Senozhatsky
2016-11-24 16:35 ` Petr Mladek
2016-12-01 1:07 ` Sergey Senozhatsky
2016-12-01 12:12 ` Petr Mladek
2016-10-27 15:49 ` [RFC][PATCHv4 3/6] printk: introduce per-cpu safe_print seq buffer Sergey Senozhatsky
2016-11-24 16:58 ` Petr Mladek
2016-12-01 1:08 ` Sergey Senozhatsky
2016-12-01 5:32 ` Sergey Senozhatsky
2016-10-27 15:49 ` [RFC][PATCHv4 4/6] printk: report lost messages in printk safe/nmi contexts Sergey Senozhatsky
2016-11-25 11:07 ` Petr Mladek
2016-12-01 2:10 ` Sergey Senozhatsky
2016-12-01 12:50 ` Petr Mladek
2016-10-27 15:49 ` [RFC][PATCHv4 5/6] printk: use printk_safe buffers Sergey Senozhatsky
2016-11-25 14:28 ` Petr Mladek
2016-12-01 2:14 ` Sergey Senozhatsky [this message]
2016-10-27 15:49 ` [RFC][PATCHv4 6/6] printk: remove zap_locks() function Sergey Senozhatsky
2016-11-25 15:01 ` Petr Mladek
2016-11-25 15:17 ` Peter Zijlstra
2016-12-01 2:34 ` Sergey Senozhatsky
2016-12-01 5:42 ` Peter Zijlstra
2016-12-01 13:36 ` Petr Mladek
2016-12-02 1:11 ` Sergey Senozhatsky
2016-12-01 2:18 ` Sergey Senozhatsky
2016-12-01 12:50 ` Sergey Senozhatsky
2016-12-01 13:15 ` Petr Mladek
2016-10-28 3:30 ` [RFC][PATCHv4 0/6] printk: use printk_safe to handle printk() recursive calls Linus Torvalds
2016-10-28 4:05 ` Sergey Senozhatsky
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