Messages in this thread | | | Date | Thu, 26 May 2022 14:09:25 +0200 | From | Petr Mladek <> | Subject | Re: [GIT PULL] printk for 5.19 |
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On Thu 2022-05-26 00:08:46, John Ogness wrote: > On 2022-05-25, Linus Torvalds <torvalds@linux-foundation.org> wrote: > > On Mon, May 23, 2022 at 6:21 AM Petr Mladek <pmladek@suse.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.
Best Regards, Petr
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