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>
This commit is contained in:
Paolo Bonzini 2014-06-05 14:53:58 +02:00 committed by Stefan Hajnoczi
parent 5d5da114b3
commit 74892d2468
4 changed files with 57 additions and 32 deletions

View file

@ -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