From: Marcelo Tosatti <mtosatti@redhat.com>
Date: Mon, 18 Mar 2013 16:54:32 +0000 (-0300)
Subject: KVM: x86: fix deadlock in clock-in-progress request handling
X-Git-Tag: v3.9-rc4~22^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c09664bb44184b3846e8c5254db4eae4b932682a;p=pandora-kernel.git

KVM: x86: fix deadlock in clock-in-progress request handling

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.

Fix by moving pvclock_gtod_sync_lock protected section outside irq
disabled section.

Analyzed by Gleb Natapov <gleb@redhat.com>
Acked-by: Gleb Natapov <gleb@redhat.com>
Reported-and-Tested-by: Yongjie Ren <yongjie.ren@intel.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---

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