From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>,
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>, 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 6/6] printk: remove zap_locks() function
Date: Thu, 1 Dec 2016 11:34:42 +0900 [thread overview]
Message-ID: <20161201023442.GH12039@jagdpanzerIV> (raw)
In-Reply-To: <20161125151724.GO3092@twins.programming.kicks-ass.net>
On (11/25/16 16:17), Peter Zijlstra wrote:
> On Fri, Nov 25, 2016 at 04:01:13PM +0100, Petr Mladek wrote:
> > On Fri 2016-10-28 00:49:33, Sergey Senozhatsky wrote:
> > > 2) Since commit cf9b1106c81c ("printk/nmi: flush NMI messages on the
> > > system panic") panic attempts to zap the `logbuf_lock' spin_lock to
> > > successfully flush nmi messages to `logbuf'.
> >
> > Note that the same code is newly used to flush also the printk_safe
> > per-CPU buffers. It means that logbuf_lock is zapped also when
> > flushing these new buffers.
> >
>
> Note that (raw_)spin_lock_init() as done here and in
> printk_nmi_flush_on_panic() can wreck the lock state and doesn't ensure
> a subsequent spin_lock() of said lock will actually work.
>
> The very best solution is to simply ignore the lock in panic situations
> rather than trying to wreck it.
do you mean that we can enterily drop the spin_lock_init()? or is there
something else? spin_lock_init() either does not improve anything or let
us to, at least, move the messages from per-CPU buffers to the logbuf. so
it's not like it does some damage, and it can help sometimes. though I
agree that a) we have the messages in the memory already and b) logbuf_lock
is not the one&only troubling lock.
-ss
next prev parent reply other threads:[~2016-12-01 2:34 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
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 [this message]
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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