linux/arch/x86/kvm/timer.c
Jan Kiszka 681405bfc7 KVM: Drop useless atomic test from timer function
The current code tries to optimize the setting of
KVM_REQ_PENDING_TIMER but used atomic_inc_and_test - which always
returns true unless pending had the invalid value of -1 on entry. This
patch drops the test part preserving the original semantic but
expressing it less confusingly.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
2009-09-10 08:32:57 +03:00

50 lines
1.2 KiB
C

#include <linux/kvm_host.h>
#include <linux/kvm.h>
#include <linux/hrtimer.h>
#include <asm/atomic.h>
#include "kvm_timer.h"
static int __kvm_timer_fn(struct kvm_vcpu *vcpu, struct kvm_timer *ktimer)
{
int restart_timer = 0;
wait_queue_head_t *q = &vcpu->wq;
/*
* There is a race window between reading and incrementing, but we do
* not care about potentially loosing timer events in the !reinject
* case anyway.
*/
if (ktimer->reinject || !atomic_read(&ktimer->pending)) {
atomic_inc(&ktimer->pending);
/* FIXME: this code should not know anything about vcpus */
set_bit(KVM_REQ_PENDING_TIMER, &vcpu->requests);
}
if (waitqueue_active(q))
wake_up_interruptible(q);
if (ktimer->t_ops->is_periodic(ktimer)) {
hrtimer_add_expires_ns(&ktimer->timer, ktimer->period);
restart_timer = 1;
}
return restart_timer;
}
enum hrtimer_restart kvm_timer_fn(struct hrtimer *data)
{
int restart_timer;
struct kvm_vcpu *vcpu;
struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
vcpu = ktimer->vcpu;
if (!vcpu)
return HRTIMER_NORESTART;
restart_timer = __kvm_timer_fn(vcpu, ktimer);
if (restart_timer)
return HRTIMER_RESTART;
else
return HRTIMER_NORESTART;
}