The call_usermodehelper_exec_[a]sync() kernel threads are created by khelper precisely because we want them to be affine to all CPUs, irrespective of any call_usermodehelper() caller with reduced CPU affinity. So this explicit all-CPUs wide affinity forcing is useless.
Not only useless it even breaks nohz full. The housekeeping work (general kernel internal code that user doesn't care much about) is handled by a reduced set of CPUs in nohz full, precisely those that are not included by nohz_full= kernel parameters. For example unbound workqueues are handled by housekeeping CPUs. And we want the usermodehelper tasks to be handled by housekeeping CPUs because they are kernel internals that user critical nohz full work don't want to be disturbed by. In nohz full configurations, khelper will naturally be affine to housekeeping CPUs and this housekeeping affinity is then inherited by usermodehelper kernel threads. But the explicit call to set_cpus_allowed_ptr() breaks that. Simply remove it. Cc: Rik van Riel <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Christoph Lameter <[email protected]> Signed-off-by: Frederic Weisbecker <[email protected]> --- kernel/kmod.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/kernel/kmod.c b/kernel/kmod.c index f940b21..b89342b 100644 --- a/kernel/kmod.c +++ b/kernel/kmod.c @@ -223,9 +223,6 @@ static int call_usermodehelper_exec_async(void *data) flush_signal_handlers(current, 1); spin_unlock_irq(¤t->sighand->siglock); - /* We can run anywhere, unlike our parent keventd(). */ - set_cpus_allowed_ptr(current, cpu_all_mask); - /* * Our parent is keventd, which runs with elevated scheduling priority. * Avoid propagating that into the userspace child. -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
