On 09/16, Tejun Heo wrote: > > From f9f9e7b776142fb1c0782cade004cc8e0147a199 Mon Sep 17 00:00:00 2001 > From: Tejun Heo <[email protected]> > 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 <[email protected]> > Link: http://lkml.kernel.org/g/[email protected] > Reported-by: Christian Borntraeger <[email protected]> > Cc: Oleg Nesterov <[email protected]> > Cc: "Paul E. McKenney" <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Paolo Bonzini <[email protected]> > Cc: [email protected] # 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 [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
