From: Tejun Heo <tj@kernel.org>
To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: 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>,
Paul McKenney <paulmck@linux.vnet.ibm.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 17:26:22 -0400 [thread overview]
Message-ID: <20150915212622.GC495@htj.duckdns.org> (raw)
In-Reply-To: <55F88991.7040406@de.ibm.com>
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.
Thanks.
--
tejun
next prev parent reply other threads:[~2015-09-15 21:26 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 [this message]
2015-09-15 21:38 ` Paul E. McKenney
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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