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    SubjectRe: [Query] Preemption (hogging) of the work handler
    +Rafael and linux-pm to this thread :)

    On 12-07-16, 14:52, Petr Mladek wrote:
    > On Tue 2016-07-12 18:38:05, Sergey Senozhatsky wrote:
    > > Hello,
    > >
    > > On (07/11/16 15:35), Viresh Kumar wrote:
    > > [..]
    > > > Sometimes, the platform doesn't come back after suspend. I have tried
    > > > enabling no-console-suspend and the last line it prints is:
    > > >
    > > > Disabling non-boot CPUs
    >
    > I guess that the printk() kthread is not longer scheduled when there
    > is only one CPU left.

    Yeah, so I tried debugging this more and I am able to get printing
    done to just before arch_suspend_disable_irqs() in suspend.c and then
    it stops because of the async nature.

    I get to this point for both successful suspend/resume (where system
    resumes back successfully) and in the bad case (where the system just
    hangs/crashes).

    FWIW, I also tried commenting out following in suspend_enter():

    error = suspend_ops->enter(state);

    so that the system doesn't go into suspend at all, and just resume
    back immediately (similar to TEST_CORE) and I saw the hang/crash then
    as well one of the times.

    > We might try to explicitly flush the consoles in suspend_console().

    That wouldn't happen as I have disabled console-suspend.

    > But I am not sure if we always want to do so because it might take
    > a while. Also it need not help if someone already owns the
    > console_sem. Note the console_unlock() calls the cond_resched()
    > when in safe context.
    >
    > Well, we might do the best effort when no_console_suspend is enabled.

    Hmm.. I have no reasoning yet on why the system comes to a complete
    stop and a forceful reboot only makes it work :(

    --
    viresh

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