On 02/08/2011 01:55 PM, Jan Kiszka wrote:
Only for walking the list of VMs, we do not need to hold the preemption
disabling kvm_lock. Convert stat services, the cpufreq callback and
mmu_shrink to RCU. For the latter, special care is required to
synchronize its list_move_tail with kvm_destroy_vm.
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index b6a9963..e9d0ed8 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3587,9 +3587,9 @@ static int mmu_shrink(struct shrinker *shrink, int nr_to_scan, gfp_t gfp_mask)
if (nr_to_scan == 0)
goto out;
- raw_spin_lock(&kvm_lock);
+ rcu_read_lock();
- list_for_each_entry(kvm,&vm_list, vm_list) {
+ list_for_each_entry_rcu(kvm,&vm_list, vm_list) {
int idx, freed_pages;
LIST_HEAD(invalid_list);
Have to #include rculist.h, and to change all list operations on vm_list
to rcu variants.
@@ -3607,10 +3607,14 @@ static int mmu_shrink(struct shrinker *shrink, int nr_to_scan, gfp_t gfp_mask)
spin_unlock(&kvm->mmu_lock);
srcu_read_unlock(&kvm->srcu, idx);
}
- if (kvm_freed)
- list_move_tail(&kvm_freed->vm_list,&vm_list);
+ if (kvm_freed) {
+ raw_spin_lock(&kvm_lock);
+ if (!kvm->deleted)
+ list_move_tail(&kvm_freed->vm_list,&vm_list);
There is no list_move_tail_rcu().
Why check kvm->deleted? it's in the process of being torn down anyway,
it doesn't matter if mmu_shrink or kvm_destroy_vm pulls the trigger.
+ raw_spin_unlock(&kvm_lock);
+ }
- raw_spin_unlock(&kvm_lock);
+ rcu_read_unlock();
--
error compiling committee.c: too many arguments to function
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