From: Paolo Bonzini <pbonzini@redhat.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>,
KVM list <kvm@vger.kernel.org>,
Cornelia Huck <cornelia.huck@de.ibm.com>,
qemu-devel <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [s390] possible deadlock in handle_sigp?
Date: Mon, 12 Sep 2016 20:03:10 +0200 [thread overview]
Message-ID: <e2702dff-0f51-a97e-e186-c1d125f6ab76@redhat.com> (raw)
In-Reply-To: <a122ac4f-a336-312a-0531-2e2a2a57f5b9@de.ibm.com>
On 12/09/2016 19:37, Christian Borntraeger wrote:
> On 09/12/2016 06:44 PM, Paolo Bonzini wrote:
> > I think that two CPUs doing reciprocal SIGPs could in principle end up
> > waiting on each other to complete their run_on_cpu. If the SIGP has to
> > be synchronous the fix is not trivial (you'd have to put the CPU in a
> > state similar to cpu->halted = 1), otherwise it's enough to replace
> > run_on_cpu with async_run_on_cpu.
>
> IIRC the sigps are supossed to be serialized by the big QEMU lock. WIll
> have a look.
Yes, but run_on_cpu drops it when it waits on the qemu_work_cond
condition variable. (Related: I stumbled upon it because I wanted to
remove the BQL from run_on_cpu work items).
Paolo
next prev parent reply other threads:[~2016-09-12 18:03 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-12 16:44 [Qemu-devel] [s390] possible deadlock in handle_sigp? Paolo Bonzini
2016-09-12 17:37 ` Christian Borntraeger
2016-09-12 18:03 ` Paolo Bonzini [this message]
2016-09-13 13:06 ` Christian Borntraeger
2016-09-15 19:21 ` David Hildenbrand
2016-09-15 20:50 ` Paolo Bonzini
2016-09-19 8:15 ` Christian Borntraeger
2016-09-19 11:25 ` David Hildenbrand
2016-09-19 11:45 ` Christian Borntraeger
2016-09-20 11:57 ` [Qemu-devel] [PATCH] s390x/kvm: Fix potential deadlock in sigp handling Christian Borntraeger
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