[Qemu-devel] Re: [PATCH] fix smp with tcg mode and --enable-io-thread

[Marcelo Tosatti]

On Mon, Jun 21, 2010 at 10:58:32PM +0200, Jan Kiszka wrote:
> Jan Kiszka wrote:
> > Marcelo Tosatti wrote:
> >> Clear exit_request when iothread grabs the global lock. 
> >>
> >> Signed-off-by: Marcelo Tosatti <mtosa...@redhat.com>
> >>
> >> diff --git a/cpu-exec.c b/cpu-exec.c
> >> index 026980a..74cb973 100644
> >> --- a/cpu-exec.c
> >> +++ b/cpu-exec.c
> >> @@ -236,10 +236,8 @@ int cpu_exec(CPUState *env1)
> >>      asm("");
> >>      env = env1;
> >>  
> >> -    if (exit_request) {
> >> +    if (exit_request)
> >>          env->exit_request = 1;
> >> -        exit_request = 0;
> >> -    }
> > 
> > Coding style...
> > 
> >>  
> >>  #if defined(TARGET_I386)
> >>      if (!kvm_enabled()) {
> >> diff --git a/cpus.c b/cpus.c
> >> index fcd0f09..ef1ab22 100644
> >> --- a/cpus.c
> >> +++ b/cpus.c
> >> @@ -598,6 +598,7 @@ void qemu_mutex_lock_iothread(void)
> >>          }
> >>          qemu_mutex_unlock(&qemu_fair_mutex);
> >>      }
> >> +   exit_request = 0;
> >>  }
> >>  
> >>  void qemu_mutex_unlock_iothread(void)
> >>
> >>
> > 
> > I looked into this a bit as well, and that's what I also have in my
> > queue.
> > 
> > But things are still widely broken: pause_all_vcpus and run_on_cpu as
> > there is no guarantee that all VCPUs regularly call into
> > qemu_wait_io_event. Also breakpoints don't work, not only in SMP mode.

This fixes pause for me:


diff --git a/cpu-exec.c b/cpu-exec.c
index c776605..0149da5 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -238,7 +238,6 @@ int cpu_exec(CPUState *env1)
 
     if (exit_request) {
         env->exit_request = 1;
-        exit_request = 0;
     }
 
 #if defined(TARGET_I386)
diff --git a/cpus.c b/cpus.c
index 826886c..14f7cfc 100644
--- a/cpus.c
+++ b/cpus.c
@@ -403,6 +403,8 @@ static void qemu_wait_io_event_common(CPUState *env)
 
 static void qemu_wait_io_event(CPUState *env)
 {
+    CPUState *e;
+
     while (!tcg_has_work())
         qemu_cond_timedwait(env->halt_cond, &qemu_global_mutex, 1000);
 
@@ -417,7 +419,9 @@ static void qemu_wait_io_event(CPUState *env)
     qemu_mutex_unlock(&qemu_fair_mutex);
 
     qemu_mutex_lock(&qemu_global_mutex);
-    qemu_wait_io_event_common(env);
+
+    for (e = first_cpu; e != NULL; e = e->next_cpu)
+        qemu_wait_io_event_common(e);
 }
 
 static void qemu_kvm_eat_signal(CPUState *env, int timeout)
@@ -614,6 +618,7 @@ void qemu_mutex_lock_iothread(void)
         }
         qemu_mutex_unlock(&qemu_fair_mutex);
     }
+   exit_request = 0;
 }
 
 void qemu_mutex_unlock_iothread(void)



Perhaps there is a similar problem with debugging (round robin 
in tcg_cpu_exec fails when there is a timer pending, and the 
iothread is not processing pending timers).