On 09/16, Tejun Heo wrote: > > From f9f9e7b776142fb1c0782cade004cc8e0147a199 Mon Sep 17 00:00:00 2001 > From: Tejun Heo <t...@kernel.org> > Date: Wed, 16 Sep 2015 11:51:12 -0400 > > This reverts commit b5ba75b5fc0e8404e2c50cb68f39bb6a53fc916f. > > d59cfc09c32a ("sched, cgroup: replace signal_struct->group_rwsem with > a global percpu_rwsem") and b5ba75b5fc0e ("cgroup: simplify > threadgroup locking") changed how cgroup synchronizes against task > fork and exits so that it uses global percpu_rwsem instead of > per-process rwsem; unfortunately, the write [un]lock paths of > percpu_rwsem always involve synchronize_rcu_expedited() which turned > out to be too expensive. > > Improvements for percpu_rwsem are scheduled to be merged in the coming > v4.4-rc1 merge window which alleviates this issue. For now, revert > the two commits to restore per-process rwsem. They will be re-applied > for the v4.4-rc1 merge window. > > Signed-off-by: Tejun Heo <t...@kernel.org> > Link: http://lkml.kernel.org/g/55f8097a.7000...@de.ibm.com > Reported-by: Christian Borntraeger <borntrae...@de.ibm.com> > Cc: Oleg Nesterov <o...@redhat.com> > Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> > Cc: Peter Zijlstra <pet...@infradead.org> > Cc: Paolo Bonzini <pbonz...@redhat.com> > Cc: sta...@vger.kernel.org # v4.2+
So just in case, I agree. Perhaps we could merge the percpu_rwsem changes in v4.3, but these patches look much safer for -stable. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/