From mboxrd@z Thu Jan  1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 55201] host panic when "creating guest, doing scp and killing
 QEMU process" continuously
Date: Thu, 14 Mar 2013 10:37:25 +0000 (UTC)
Message-ID: <20130314103725.58D2711F877@bugzilla.kernel.org>
References: <bug-55201-28872@https.bugzilla.kernel.org/>
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https://bugzilla.kernel.org/show_bug.cgi?id=55201


Gleb <gleb@redhat.com> changed:

           What    |Removed                     |Added
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                 CC|                            |gleb@redhat.com




--- Comment #3 from Gleb <gleb@redhat.com>  2013-03-14 10:37:25 ---
There is a deadlock in pvclock handling:

cpu0:                                               cpu1:
kvm_gen_update_masterclock()
                                              kvm_guest_time_update()
 spin_lock(pvclock_gtod_sync_lock)
                                               local_irq_save(flags)
                                              
spin_lock(pvclock_gtod_sync_lock)

 kvm_make_mclock_inprogress_request(kvm)
  make_all_cpus_request()
   smp_call_function_many()


Now if smp_call_function_many() called by cpu0 tries to call function on cpu1
there will be a deadlock. It shouldn't do it though since
make_all_cpus_request() is careful to not IPI to cpus that are not in a guest
mode and cpu1 is not in a guest mode. The only way I see the deadlock may
happen is if make_all_cpus_request() fails to allocate "cpus" cpu mask in which
case it IPIs all online cpus.

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