On Tue, Oct 2, 2018 at 1:42 AM Petr Mladek <pmladek@xxxxxxxx> wrote: > Well, I still wonder why it helped and why you do not see it with 4.4. > I have a feeling that the console owner switch helped only by chance. So do I. I don't think Steven had the deadlock in mind when working on that patch, but with that patch and that patch alone, the deadlock disappeared. > In fact, you might be affected by a race in > printk_safe_flush_on_panic() that was fixed by the commit: > > 554755be08fba31c7 printk: drop in_nmi check from printk_safe_flush_on_panic() > > The above one commit might be enough. Well, there was one more Thanks for the pointer. Let me test this out. > NMI-related race that was fixed by: > > ba552399954dde1b printk: Split the code for storing a message into the log buffer > a338f84dc196f44b printk: Create helper function to queue deferred console handling > 03fc7f9c99c1e7ae printk/nmi: Prevent deadlock when accessing the main log buffer in NMI > > Best Regards, > Petr On Tue, Oct 2, 2018 at 1:17 AM Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx> wrote: > Sorry, I'm missing something here. Steven's patch deals with lockups and > I understand why you want to backport the patch set; but console output > deadlock on panic() is another thing. Understood. But it did fix the deadlock for me and without it I hit the deadlock pretty consistently. Let me test the patch Petr pointed out and will update here. -- Best, Daniel
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