From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Byungchul Park <byungchul.park@lge.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Jan Kara <jack@suse.com>, Petr Mladek <pmladek@suse.com>,
Tejun Heo <tj@kernel.org>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH v4 1/2] printk: Make printk() completely async
Date: Wed, 16 Mar 2016 16:56:05 +0900 [thread overview]
Message-ID: <20160316075605.GE3217@swordfish> (raw)
In-Reply-To: <20160316073007.GL5220@X58A-UD3R>
On (03/16/16 16:30), Byungchul Park wrote:
>
> Do you mean the wake_up_process() in console_unlock?
no, I meant wake_up_process(printk_kthread), the newly added one.
-- if we are going to have wake_up_process() in wake_up_klogd_work_func(),
then we need `in_sched' message to potentially trigger a recursion chain
wake_up_klogd_work_func()->wake_up_process()->printk()->wake_up_process()->printk()...
to break this printk()->wake_up_process()->printk(), we need wake_up_process() to
be under the logbuf lock; so vprintk_emit()'s if (logbuf_cpu == this_cpu) will act.
-- if we are going to have wake_up_process() in console_unlock(), then
console_unlock()->{up(), wake_up_process()}->printk()->{console_lock(), console_unlock()}->{up(), wake_up_process()}->printk()...
is undetectable... by the time console_unlock() calls wake_up_process() there
are no printk() locks that this CPU owns.
> I said they should be kept *out of* the critical section. :-)
> Otherwise, it can recurse us forever.
can you explain?
-ss
next prev parent reply other threads:[~2016-03-16 7:56 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-14 14:13 [RFC][PATCH v4 0/2] printk: Make printk() completely async Sergey Senozhatsky
2016-03-14 14:13 ` [RFC][PATCH v4 1/2] " Sergey Senozhatsky
2016-03-15 10:03 ` Jan Kara
2016-03-15 14:07 ` Sergey Senozhatsky
2016-03-16 5:39 ` Byungchul Park
2016-03-16 6:58 ` Sergey Senozhatsky
2016-03-16 7:30 ` Byungchul Park
2016-03-16 7:56 ` Sergey Senozhatsky [this message]
2016-03-16 10:34 ` Byungchul Park
2016-03-17 0:34 ` Sergey Senozhatsky
2016-03-18 5:49 ` Byungchul Park
2016-03-18 7:11 ` Sergey Senozhatsky
2016-03-18 8:23 ` byungchul.park
2016-03-16 7:00 ` Byungchul Park
2016-03-16 7:07 ` Sergey Senozhatsky
2016-03-15 15:58 ` Petr Mladek
2016-03-16 2:01 ` Sergey Senozhatsky
2016-03-16 2:10 ` Byungchul Park
2016-03-16 2:31 ` Sergey Senozhatsky
2016-03-14 14:13 ` [RFC][PATCH v4 2/2] printk: Skip messages on oops Sergey Senozhatsky
2016-03-17 10:56 ` Sergey Senozhatsky
2016-04-23 19:36 ` [RFC][PATCH v4 0/2] printk: Make printk() completely async Pavel Machek
2016-04-24 5:03 ` Sergey Senozhatsky
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