vl: allow other threads to do qemu_system_vmstop_request

There patch protects vmstop_requested with a lock and introduces
qemu_system_vmstop_request_prepare.

Together with the new call to qemu_vmstop_requested in vm_start,
qemu_system_vmstop_request_prepare avoids a race where the VM could remain
stopped even though the iostatus of a block device has already been set
(for example).

qemu_system_vmstop_request_prepare however also lets the caller thread
delay observation of the state change until it has itself communicated
that change to the user.  This delay avoids any possibility of a wrong
reordering of the BLOCK_IO_ERROR event and the subsequent STOP event.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/target-lm32/op_helper.c b/target-lm32/op_helper.c
index 308742a..61209c1 100644
--- a/target-lm32/op_helper.c
+++ b/target-lm32/op_helper.c
@@ -42,7 +42,7 @@ void HELPER(ill)(CPULM32State *env)
     fprintf(stderr, "VM paused due to illegal instruction. "
             "Connect a debugger or switch to the monitor console "
             "to find out more.\n");
-    qemu_system_vmstop_request(RUN_STATE_PAUSED);
+    vm_stop(RUN_STATE_PAUSED);
     cs->halted = 1;
     raise_exception(env, EXCP_HALTED);
 #endif