• Peter Zijlstra's avatar
    sched/cpuset/pm: Fix cpuset vs. suspend-resume bugs · ba15518c
    Peter Zijlstra authored
    commit 50e76632 upstream.
    
    Cpusets vs. suspend-resume is _completely_ broken. And it got noticed
    because it now resulted in non-cpuset usage breaking too.
    
    On suspend cpuset_cpu_inactive() doesn't call into
    cpuset_update_active_cpus() because it doesn't want to move tasks about,
    there is no need, all tasks are frozen and won't run again until after
    we've resumed everything.
    
    But this means that when we finally do call into
    cpuset_update_active_cpus() after resuming the last frozen cpu in
    cpuset_cpu_active(), the top_cpuset will not have any difference with
    the cpu_active_mask and this it will not in fact do _anything_.
    
    So the cpuset configuration will not be restored. This was largely
    hidden because we would unconditionally create identity domains and
    mobile users would not in fact use cpusets much. And servers what do use
    cpusets tend to not suspend-resume much.
    
    An addition problem is that we'd not in fact wait for the cpuset work to
    finish before resuming the tasks, allowing spurious migrations outside
    of the specified domains.
    
    Fix the rebuild by introducing cpuset_force_rebuild() and fix the
    ordering with cpuset_wait_for_hotplug().
    Reported-by: 's avatarAndy Lutomirski <luto@kernel.org>
    Signed-off-by: 's avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: <stable@vger.kernel.org>
    Cc: Andy Lutomirski <luto@amacapital.net>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
    Cc: Tejun Heo <tj@kernel.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Fixes: deb7aa30 ("cpuset: reorganize CPU / memory hotplug handling")
    Link: http://lkml.kernel.org/r/20170907091338.orwxrqkbfkki3c24@hirez.programming.kicks-ass.netSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
    Signed-off-by: 's avatarMike Galbraith <efault@gmx.de>
    Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    
    ba15518c