Fix race condition on access to env->interrupt_request

env->interrupt_request is accessed as the bit level from both main code
and signal handler, making a race condition possible even on CISC CPU.
This causes freeze of QEMU under high load when running the dyntick
clock.

The patch below move the bit corresponding to CPU_INTERRUPT_EXIT in a
separate variable, declared as volatile sig_atomic_t, so it should be
work even on RISC CPU.

We may want to move the cpu_interrupt(env, CPU_INTERRUPT_EXIT) case in
its own function and get rid of CPU_INTERRUPT_EXIT. That can be done
later, I wanted to keep the patch short for easier review.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/branches/stable_0_10_0@6729 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 3 insertions, 3 deletions

diff --git a/kvm-all.c b/kvm-all.c
index 0b1742709b..28c9c07ccb 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -445,7 +445,7 @@ int kvm_cpu_exec(CPUState *env)
     do {
         kvm_arch_pre_run(env, run);
 
-        if ((env->interrupt_request & CPU_INTERRUPT_EXIT)) {
+        if (env->exit_request) {
             dprintf("interrupt exit requested\n");
             ret = 0;
             break;
@@ -512,8 +512,8 @@ int kvm_cpu_exec(CPUState *env)
         }
     } while (ret > 0);
 
-    if ((env->interrupt_request & CPU_INTERRUPT_EXIT)) {
-        env->interrupt_request &= ~CPU_INTERRUPT_EXIT;
+    if (env->exit_request) {
+        env->exit_request = 0;
         env->exception_index = EXCP_INTERRUPT;
     }