Re: [Qemu-devel] [PULL 08/21] rcu: run RCU callbacks under the BQL

[Paolo Bonzini]

On 25/02/2015 18:16, Leon Alrae wrote:
> Hi,
> 
> On 16/02/2015 18:17, Paolo Bonzini wrote:
>> This needs to go away sooner or later, but one complication is the
>> complex VFIO data structures that are modified in instance_finalize.
>> Take a shortcut for now.
> 
> It looks like this commit introduced a race condition. QEMU segfaults
> very early in one of my tests where I boot Linux, and on one of my
> machines it's easier to reproduce than on the others.

This should be enough to fix it.  If it works for you I'll send a pull
request as soon as possible.

diff --git a/cpus.c b/cpus.c
index 1cd9867..7bed67b 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1115,7 +1115,7 @@ bool qemu_in_vcpu_thread(void)

 void qemu_mutex_lock_iothread(void)
 {
-    if (!tcg_enabled()) {
+    if (!tcg_enabled() || !first_cpu) {
         qemu_mutex_lock(&qemu_global_mutex);
     } else {
         iothread_requesting_mutex = true;

Paolo