2010-12-09 18:42:29

by Thomas Meyer

Subject: [PATCH] Fix preempt imbalance in kvm_timer_init()

Signed-off-by: Thomas Meyer <[email protected]>
---
arch/x86/kvm/x86.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cdac9e5..2609c3d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4561,7 +4561,7 @@ static struct notifier_block kvmclock_cpu_notifier_block = {

static void kvm_timer_init(void)
{
- int cpu;
+ int cpu = get_cpu();

max_tsc_khz = tsc_khz;
register_hotcpu_notifier(&kvmclock_cpu_notifier_block);
@@ -4569,13 +4569,14 @@ static void kvm_timer_init(void)
#ifdef CONFIG_CPU_FREQ
struct cpufreq_policy policy;
memset(&policy, 0, sizeof(policy));
- cpufreq_get_policy(&policy, get_cpu());
+ cpufreq_get_policy(&policy, cpu);
if (policy.cpuinfo.max_freq)
max_tsc_khz = policy.cpuinfo.max_freq;
#endif
cpufreq_register_notifier(&kvmclock_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
}
+ put_cpu();
pr_debug("kvm: max_tsc_khz = %ld\n", max_tsc_khz);
for_each_online_cpu(cpu)
smp_call_function_single(cpu, tsc_khz_changed, NULL, 1);
--
1.7.3.3

2010-12-12 09:28:37

by Avi Kivity

Subject: Re: [PATCH] Fix preempt imbalance in kvm_timer_init()

On 12/09/2010 08:42 PM, Thomas Meyer wrote:
> Signed-off-by: Thomas Meyer<[email protected]>
> ---
> arch/x86/kvm/x86.c | 5 +++--
> 1 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index cdac9e5..2609c3d 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4561,7 +4561,7 @@ static struct notifier_block kvmclock_cpu_notifier_block = {
>
> static void kvm_timer_init(void)
> {
> - int cpu;
> + int cpu = get_cpu();
>
> max_tsc_khz = tsc_khz;
> register_hotcpu_notifier(&kvmclock_cpu_notifier_block);

This eventually takes a mutex (in cpu_maps_update_begin()), so it can't
be called with preemption disabled.

> @@ -4569,13 +4569,14 @@ static void kvm_timer_init(void)
> #ifdef CONFIG_CPU_FREQ
> struct cpufreq_policy policy;
> memset(&policy, 0, sizeof(policy));
> - cpufreq_get_policy(&policy, get_cpu());
> + cpufreq_get_policy(&policy, cpu);
> if (policy.cpuinfo.max_freq)
> max_tsc_khz = policy.cpuinfo.max_freq;
> #endif
> cpufreq_register_notifier(&kvmclock_cpufreq_notifier_block,
> CPUFREQ_TRANSITION_NOTIFIER);
> }
> + put_cpu();
> pr_debug("kvm: max_tsc_khz = %ld\n", max_tsc_khz);
> for_each_online_cpu(cpu)
> smp_call_function_single(cpu, tsc_khz_changed, NULL, 1);


--
error compiling committee.c: too many arguments to function