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    SubjectRe: [PATCH 09/10] sigtimedwait: use freezable blocking call
    On 04/29, Colin Cross wrote:
    >
    > Avoid waking up every thread sleeping in a sigtimedwait call during
    > suspend and resume by calling a freezable blocking call.

    This doesn't explain why do want this change...

    OK, probably to avoid -EAGAIN from sigtimedwait() if the freezer wakes
    up the caller.

    > --- a/kernel/signal.c
    > +++ b/kernel/signal.c
    > @@ -2845,7 +2845,7 @@ int do_sigtimedwait(const sigset_t *which, siginfo_t *info,
    > recalc_sigpending();
    > spin_unlock_irq(&tsk->sighand->siglock);
    >
    > - timeout = schedule_timeout_interruptible(timeout);
    > + timeout = freezable_schedule_timeout_interruptible(timeout);

    And I guess freezable_schedule_timeout_interruptible() is added by
    http://marc.info/?l=linux-kernel&m=136727195719575 ...

    +#define freezable_schedule_timeout_interruptible(timeout) \
    +({ \
    + long __retval; \
    + freezer_do_not_count(); \
    + __retval = schedule_timeout_interruptible(timeout); \
    + freezer_count(); \
    + __retval; \
    +})

    How this can help?

    The task will be interrupted anyway and the syscall will return
    -EAGAIN, this only changes the time when try_to_freeze() is called.

    For what? The task will call do_signal/try_to_freeze really "soon".

    Confused...

    Oleg.



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