Re: [PATCH v3 01/16] job.c: make job_mutex and job_lock/unlock() public

[Paolo Bonzini]

On 1/5/22 15:01, Emanuele Giuseppe Esposito wrote:
job mutex will be used to protect the job struct elements and list,
replacing AioContext locks.
Right now use a shared lock for all jobs, in order to keep things
simple. Once the AioContext lock is gone, we can introduce per-job
locks.

Not even needed in my opinion, this is not a fast path.  But we'll see.

To simplify the switch from aiocontext to job lock, introduce
*nop* lock/unlock functions and macros. Once everything is protected
by jobs, we can add the mutex and remove the aiocontext.

Since job_mutex is already being used, add static
real_job_{lock/unlock}.

Out of curiosity, what breaks if the real job lock is used from the 
start?  (It probably should be mentioned in the commit message).


-static void job_lock(void)
+static void real_job_lock(void)
  {
      qemu_mutex_lock(&job_mutex);
  }
  
-static void job_unlock(void)
+static void real_job_unlock(void)
  {
      qemu_mutex_unlock(&job_mutex);
  }

Would it work to

#define job_lock real_job_lock
#define job_unlock real_job_unlock

instead of having to do the changes below?

Paolo

@@ -449,21 +460,21 @@ void job_enter_cond(Job *job, bool(*fn)(Job *job))
          return;
      }
  
-    job_lock();
+    real_job_lock();
      if (job->busy) {
-        job_unlock();
+        real_job_unlock();
          return;
      }
  
      if (fn && !fn(job)) {
-        job_unlock();
+        real_job_unlock();
          return;
      }
  
      assert(!job->deferred_to_main_loop);
      timer_del(&job->sleep_timer);
      job->busy = true;
-    job_unlock();
+    real_job_unlock();
      aio_co_enter(job->aio_context, job->co);
  }
  
@@ -480,13 +491,13 @@ void job_enter(Job *job)
   * called explicitly. */
  static void coroutine_fn job_do_yield(Job *job, uint64_t ns)
  {
-    job_lock();
+    real_job_lock();
      if (ns != -1) {
          timer_mod(&job->sleep_timer, ns);
      }
      job->busy = false;
      job_event_idle(job);
-    job_unlock();
+    real_job_unlock();
      qemu_coroutine_yield();
  
      /* Set by job_enter_cond() before re-entering the coroutine.  */