Discard process' pending request upon incoming PM request

When a process wants something done from VFS, but VFS has no worker
threads available, the request is stored and executed later. However,
when PM also sends a request for that process at the same time, discard
the pending request from the process and give priority to PM. The request
PM sends is either an EXIT or a DUMPCORE request, so we're not interested
in executing the pending request anyway.

diff --git a/servers/avfs/main.c b/servers/avfs/main.c
index eccfc82a5bd9bca427c7407af8e799f94b16d519..02deb4ce9d0983a660e758e01781c21dafe58b09 100644 (file)
--- a/servers/avfs/main.c
+++ b/servers/avfs/main.c
@@ -881,9 +881,15 @@ PRIVATE void service_pm()
        okendpt(m_in.PM_PROC, &slot);
        fp = &fproc[slot];
 
-       assert(!(fp->fp_flags & FP_PENDING));
-       fp->fp_job.j_m_in = m_in;
-       fp->fp_flags |= FP_PM_PENDING;
+       if (fp->fp_flags & FP_PENDING) {
+               /* This process has a request pending, but PM wants it gone.
+                * Forget about the pending request and satisfy PM's request
+                * instead. Note that a pending request AND an EXEC request
+                * are mutually exclusive. Also, PM should send only one
+                * request/process at a time.
+                */
+                assert(fp->fp_job.j_m_in.m_source != PM_PROC_NR);
+       }
 
         /* PM requests on behalf of a proc are handled after the system call
          * that might be in progress for that proc has finished. If the proc
@@ -891,9 +897,11 @@ PRIVATE void service_pm()
        if (!(fp->fp_flags & FP_PENDING) && mutex_trylock(&fp->fp_lock) == 0) {
                mutex_unlock(&fp->fp_lock);
                worker_start(do_dummy);
-               yield();
         }
 
+       fp->fp_job.j_m_in = m_in;
+       fp->fp_flags |= FP_PM_PENDING;
+
        return;
 
     case PM_FORK: