From: Petr Mladek <firstname.lastname@example.org>
To: John Ogness <email@example.com>
Cc: Linus Torvalds <firstname.lastname@example.org>,
Sergey Senozhatsky <email@example.com>,
Steven Rostedt <firstname.lastname@example.org>,
Andy Shevchenko <email@example.com>,
Rasmus Villemoes <firstname.lastname@example.org>,
Jan Kara <email@example.com>, Peter Zijlstra <firstname.lastname@example.org>,
Linux Kernel Mailing List <email@example.com>
Subject: Re: [GIT PULL] printk for 5.19
Date: Thu, 26 May 2022 14:09:25 +0200 [thread overview]
Message-ID: <Yo9t9Vg/DpvMqCs7@alley> (raw)
On Thu 2022-05-26 00:08:46, John Ogness wrote:
> On 2022-05-25, Linus Torvalds <firstname.lastname@example.org> wrote:
> > On Mon, May 23, 2022 at 6:21 AM Petr Mladek <email@example.com> wrote:
> >> There are situations when the kthreads are either not available or
> >> not reliable, for example, early boot, suspend, or panic. In these
> >> situations, printk() uses the legacy mode and tries to handle
> >> consoles immediately.
> > Looking through the commits, I don't see how that "printk: wake up all
> > waiters" makes any sense at all.
> > It *ALREADY* woke up all waiters as far as I can see.
> > Doing a wake_up_interruptible() will stop waking things up only when
> > it hits a *exclusive* waiter, and as far as I can tell, there are no
> > exclusive waiters there.
> You are correct. @log_wait never has exclusive waiters. I will post a
> patch to revert the change in question.
John, Yes, please do so.
> > But when I see something really core like printk() get confused and
> > mis-understand basic wait queue behavior, that makes me go "This is
> > WRONG".
Linus, thanks a lot for catching and explaining the problem.
Yeah, it is a shame. I have met code with exclusive waiters only once,
8 years ago and completely forgot about it. I was curious how it
worked with more log waiters but I put it into TODO list. The new
code looked safe and I was too focused on finding potential problems.
next prev parent reply other threads:[~2022-05-26 12:09 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-23 13:21 [GIT PULL] printk for 5.19 Petr Mladek
2022-05-25 18:09 ` Linus Torvalds
2022-05-25 22:02 ` John Ogness
2022-05-26 12:09 ` Petr Mladek [this message]
2022-05-26 17:13 ` Linus Torvalds
2022-05-25 18:37 ` pr-tracker-bot
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