From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Tejun Heo <tj@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
"linux-kernel@vger.kernel.org >> Linux Kernel Mailing List"
<linux-kernel@vger.kernel.org>, KVM list <kvm@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>
Subject: Re: [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm
Date: Tue, 15 Sep 2015 14:38:30 -0700 [thread overview]
Message-ID: <20150915213830.GR4029@linux.vnet.ibm.com> (raw)
In-Reply-To: <20150915212622.GC495@htj.duckdns.org>
On Tue, Sep 15, 2015 at 05:26:22PM -0400, Tejun Heo wrote:
> Hello,
>
> On Tue, Sep 15, 2015 at 11:11:45PM +0200, Christian Borntraeger wrote:
> > > In fact, I would say that any userspace-controlled call to *_expedited()
> > > is a bug waiting to happen and a bad idea---because userspace can, with
> > > little effort, end up calling it in a loop.
> >
> > Right. This also implies that we should fix this for 4.2 - I guess.
>
> Are the percpu_rwsem changes enough? If so, we can try to backport
> those. If those are too risky, we can revert the patches which
> switched threadgroup lock to percpu_rwsem.
I did take a shot at adding the rcu_sync stuff during this past merge
window, but it did not converge quickly enough to make it. It looks
quite good for the next merge window. There have been changes in most
of the relevant areas, so probably best to just try them and see which
works best.
Thanx, Paul
next prev parent reply other threads:[~2015-09-15 21:38 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-15 12:05 [4.2] commit d59cfc09c32 (sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem) causes regression for libvirt/kvm Christian Borntraeger
2015-09-15 13:05 ` Peter Zijlstra
2015-09-15 13:36 ` Christian Borntraeger
2015-09-15 13:53 ` Tejun Heo
2015-09-15 16:42 ` Paolo Bonzini
2015-09-15 17:38 ` Paul E. McKenney
2015-09-16 8:32 ` Paolo Bonzini
2015-09-16 8:57 ` Christian Borntraeger
2015-09-16 9:12 ` Paolo Bonzini
2015-09-16 12:22 ` Oleg Nesterov
2015-09-16 12:35 ` Paolo Bonzini
2015-09-16 12:43 ` Oleg Nesterov
2015-09-16 12:56 ` Christian Borntraeger
2015-09-16 14:16 ` Tejun Heo
2015-09-16 14:19 ` Paolo Bonzini
2015-09-15 21:11 ` Christian Borntraeger
2015-09-15 21:26 ` Tejun Heo
2015-09-15 21:38 ` Paul E. McKenney [this message]
2015-09-15 22:28 ` Tejun Heo
2015-09-15 23:38 ` Paul E. McKenney
2015-09-16 1:24 ` Tejun Heo
2015-09-16 4:35 ` Paul E. McKenney
2015-09-16 11:06 ` Tejun Heo
2015-09-16 7:44 ` Christian Borntraeger
2015-09-16 10:58 ` Christian Borntraeger
2015-09-16 11:03 ` Tejun Heo
2015-09-16 11:50 ` Christian Borntraeger
2015-09-16 15:55 ` [PATCH cgroup/for-4.3-fixes 1/2] Revert "cgroup: simplify threadgroup locking" Tejun Heo
2015-09-16 15:56 ` [PATCH cgroup/for-4.3-fixes 2/2] Revert "sched, cgroup: replace signal_struct->group_rwsem with a global percpu_rwsem" Tejun Heo
2015-09-16 17:00 ` [PATCH cgroup/for-4.3-fixes 1/2] Revert "cgroup: simplify threadgroup locking" Oleg Nesterov
2015-09-16 18:45 ` Christian Borntraeger
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