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| author | Marcelo Tosatti <mtosatti@redhat.com> | 2008-05-08 19:47:01 -0300 |
|---|---|---|
| committer | Avi Kivity <avi@qumranet.com> | 2008-05-18 14:37:12 +0300 |
| commit | e5c239cfd5b0ec22751c099dbf4d91f3c504a64f (patch) | |
| tree | d0a63882f0592a4ce23a98478fb9c935213b2e16 /virt | |
| parent | bd25ed033af52c8c054d43a9cce9c5976266ae74 (diff) | |
| download | lwn-e5c239cfd5b0ec22751c099dbf4d91f3c504a64f.tar.gz lwn-e5c239cfd5b0ec22751c099dbf4d91f3c504a64f.zip | |
KVM: Fix kvm_vcpu_block() task state race
There's still a race in kvm_vcpu_block(), if a wake_up_interruptible()
call happens before the task state is set to TASK_INTERRUPTIBLE:
CPU0 CPU1
kvm_vcpu_block
add_wait_queue
kvm_cpu_has_interrupt = 0
set interrupt
if (waitqueue_active())
wake_up_interruptible()
kvm_cpu_has_pending_timer
kvm_arch_vcpu_runnable
signal_pending
set_current_state(TASK_INTERRUPTIBLE)
schedule()
Can be fixed by using prepare_to_wait() which sets the task state before
testing for the wait condition.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
Diffstat (limited to 'virt')
| -rw-r--r-- | virt/kvm/kvm_main.c | 29 |
1 files changed, 15 insertions, 14 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index f7ba099049ea..2d29e260da3d 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -758,25 +758,26 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn) */ void kvm_vcpu_block(struct kvm_vcpu *vcpu) { - DECLARE_WAITQUEUE(wait, current); - - add_wait_queue(&vcpu->wq, &wait); - - /* - * We will block until either an interrupt or a signal wakes us up - */ - while (!kvm_cpu_has_interrupt(vcpu) - && !kvm_cpu_has_pending_timer(vcpu) - && !signal_pending(current) - && !kvm_arch_vcpu_runnable(vcpu)) { - set_current_state(TASK_INTERRUPTIBLE); + DEFINE_WAIT(wait); + + for (;;) { + prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE); + + if (kvm_cpu_has_interrupt(vcpu)) + break; + if (kvm_cpu_has_pending_timer(vcpu)) + break; + if (kvm_arch_vcpu_runnable(vcpu)) + break; + if (signal_pending(current)) + break; + vcpu_put(vcpu); schedule(); vcpu_load(vcpu); } - __set_current_state(TASK_RUNNING); - remove_wait_queue(&vcpu->wq, &wait); + finish_wait(&vcpu->wq, &wait); } void kvm_resched(struct kvm_vcpu *vcpu) |