kernel/sched-kvm-Fix-KVM-preempt_notifier-usage.patch
Josh Boyer 6a50f36878 Linux v4.1-11355-g6aaf0da8728c
- Add patch to fix KVM sleeping in atomic issue (rhbz 1237143)
- Fix errant with_perf disable that removed perf entirely (rhbz 1237266)
2015-06-30 13:01:28 -04:00

81 lines
2.6 KiB
Diff

From: Peter Zijlstra <peterz@infradead.org>
Date: Thu, 25 Jun 2015 14:55:14 +0200
Subject: [PATCH] sched,kvm: Fix KVM preempt_notifier usage
The preempt-notifier API needs to sleep with the addition of the
static_key, we do however need to hold off preemption while modifying
the preempt notifier list, otherwise a preemption could observe an
inconsistent list state.
There is no reason to have preemption disabled in the caller,
registering a preempt notifier is a purely task local affair.
Therefore move the preempt_disable into the functions and change the
callers to a preemptible context.
Cc: Gleb Natapov <gleb@kernel.org>
Fixes: 1cde2930e154 ("sched/preempt: Add static_key() to preempt_notifiers")
Reported-and-Tested-by: Pontus Fuchs <pontus.fuchs@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/sched/core.c | 11 +++++++++++
virt/kvm/kvm_main.c | 5 +++--
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b803e1b8ab0c..6169c167ac98 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2327,7 +2327,12 @@ static struct static_key preempt_notifier_key = STATIC_KEY_INIT_FALSE;
void preempt_notifier_register(struct preempt_notifier *notifier)
{
static_key_slow_inc(&preempt_notifier_key);
+ /*
+ * Avoid preemption while changing the preempt notifier list.
+ */
+ preempt_disable();
hlist_add_head(&notifier->link, &current->preempt_notifiers);
+ preempt_enable();
}
EXPORT_SYMBOL_GPL(preempt_notifier_register);
@@ -2339,7 +2344,13 @@ EXPORT_SYMBOL_GPL(preempt_notifier_register);
*/
void preempt_notifier_unregister(struct preempt_notifier *notifier)
{
+ /*
+ * Avoid preemption while changing the preempt notifier list.
+ */
+ preempt_disable();
hlist_del(&notifier->link);
+ preempt_enable();
+
static_key_slow_dec(&preempt_notifier_key);
}
EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 848af90b8091..7dc8d3eb9e1f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -127,8 +127,9 @@ int vcpu_load(struct kvm_vcpu *vcpu)
if (mutex_lock_killable(&vcpu->mutex))
return -EINTR;
- cpu = get_cpu();
preempt_notifier_register(&vcpu->preempt_notifier);
+
+ cpu = get_cpu();
kvm_arch_vcpu_load(vcpu, cpu);
put_cpu();
return 0;
@@ -138,8 +139,8 @@ void vcpu_put(struct kvm_vcpu *vcpu)
{
preempt_disable();
kvm_arch_vcpu_put(vcpu);
- preempt_notifier_unregister(&vcpu->preempt_notifier);
preempt_enable();
+ preempt_notifier_unregister(&vcpu->preempt_notifier);
mutex_unlock(&vcpu->mutex);
}