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kvm,x86: Fix apf_task_wake_one() wq serialization
authorDavidlohr Bueso <dave@stgolabs.net>
Wed, 13 Sep 2017 20:08:21 +0000 (13:08 -0700)
committerPaolo Bonzini <pbonzini@redhat.com>
Fri, 15 Sep 2017 14:57:12 +0000 (16:57 +0200)
commita0cff57bb2a41cb9cbf13d3203097b4156d8c0ae
treedb128f5fac2c228a01f314174b20db01b3412316tree | snapshot
parentcc1b46803a671047be22f7832ef4a2bb3f63dd94commit | diff
kvm,x86: Fix apf_task_wake_one() wq serialization

During code inspection, the following potential race was seen:

CPU0                    CPU1
kvm_async_pf_task_wait apf_task_wake_one
  [L] swait_active(&n->wq)
  [S] prepare_to_swait(&n.wq)
  [L] if (!hlist_unhahed(&n.link))
schedule()   [S] hlist_del_init(&n->link);

Properly serialize swait_active() checks such that a wakeup is
not missed.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
arch/x86/kernel/kvm.c diff | blob | history
Domain: System / Kernel; Licenses: GPL-2.0;