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    SubjectRe: [PATCH] PM/Freezer: Thaw only kernel threads if freezing of kernel threads fails
    Date
    On Wednesday, February 01, 2012, Tejun Heo wrote:
    > On Thu, Feb 02, 2012 at 04:01:12AM +0530, Srivatsa S. Bhat wrote:
    > > If freezing of kernel threads fails, we are expected to automatically thaw
    > > tasks in the error recovery path. However, at times, we encounter situations
    > > in which we would like the automatic error recovery path to thaw only the
    > > kernel threads, because we want to be able to do some more cleanup before
    > > we thaw userspace. Something like:
    > >
    > > error = freeze_kernel_threads();
    > > if (error) {
    > > /* Do some cleanup */
    > >
    > > /* Only then thaw userspace tasks*/
    > > thaw_processes();
    > > }
    > >
    > > An example of such a situation is where we freeze/thaw filesystems during
    > > suspend/hibernation. There, if freezing of kernel threads fails, we would
    > > like to thaw the frozen filesystems before thawing the userspace tasks.
    > >
    > > So, modify freeze_kernel_threads() to thaw only kernel threads in case of
    > > freezing failure.
    > >
    > > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    >
    > Acked-by: Tejun Heo <tj@kernel.org>
    >
    > with nits below,
    >
    > > ---
    > >
    > > kernel/power/power.h | 26 ++++++++++++++++++++++++--
    > > kernel/power/process.c | 7 +++++--
    > > 2 files changed, 29 insertions(+), 4 deletions(-)
    > >
    > > diff --git a/kernel/power/power.h b/kernel/power/power.h
    > > index 0c4defe..cf41c03 100644
    > > --- a/kernel/power/power.h
    > > +++ b/kernel/power/power.h
    > > @@ -231,8 +231,30 @@ extern int pm_test_level;
    > > #ifdef CONFIG_SUSPEND_FREEZER
    > > static inline int suspend_freeze_processes(void)
    > > {
    > > - int error = freeze_processes();
    > > - return error ? : freeze_kernel_threads();
    > > + int error;
    > > +
    > > + error = freeze_processes();
    > > +
    > > + /*
    > > + * freeze_processes() automatically thaws
    > > + * every task if freezing fails. So we need
    > > + * not do anything extra upon error.
    > > + */
    > > + if (error)
    > > + goto Finish;
    > > +
    > > + error = freeze_kernel_threads();
    > > +
    > > + /*
    > > + * freeze_kernel_threads() thaws only kernel
    > > + * threads upon freezing failure. So we have
    > > + * to thaw the userspace tasks ourselves.
    > > + */
    > > + if (error)
    > > + thaw_processes();
    > > +
    > > + Finish:
    > > + return error;
    >
    > Heh, the original ?: code was scary.

    C'mon. ;-)

    > That said, IMHO, the above seems
    > a bit too verbose. Functions usually shouldn't have side effects on
    > failure and the above code is usual in that sense and it would be nice
    > to mention the reformatting (from cryptic to sane) in the commit log.
    > Also, how many columns are you flowing the text to? It seems quite
    > narrower than they usually should be.

    I agree.

    Srivatsa, care to resubmit?

    Rafael


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