diff options
Diffstat (limited to 'sched-kvm-Fix-KVM-preempt_notifier-usage.patch')
| -rw-r--r-- | sched-kvm-Fix-KVM-preempt_notifier-usage.patch | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/sched-kvm-Fix-KVM-preempt_notifier-usage.patch b/sched-kvm-Fix-KVM-preempt_notifier-usage.patch new file mode 100644 index 000000000..958b7fa98 --- /dev/null +++ b/sched-kvm-Fix-KVM-preempt_notifier-usage.patch @@ -0,0 +1,80 @@ +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(¬ifier->link, ¤t->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(¬ifier->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); + } + |