Initial revision

1 files changed, 112 insertions, 0 deletions

diff --git a/libthreads/cancel-cond.c b/libthreads/cancel-cond.c
new file mode 100644
index 00000000..8a55fba4
--- /dev/null
+++ b/libthreads/cancel-cond.c
@@ -0,0 +1,112 @@
+/* Modified condition_wait that checks for cancellation.
+Copyright (C) 1995 Free Software Foundation, Inc.
+This file is part of the GNU C Library.
+
+The GNU C Library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Library General Public License as
+published by the Free Software Foundation; either version 2 of the
+License, or (at your option) any later version.
+
+The GNU C Library is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+Library General Public License for more details.
+
+You should have received a copy of the GNU Library General Public
+License along with the GNU C Library; see the file COPYING.LIB.  If
+not, write to the Free Software Foundation, Inc., 675 Mass Ave,
+Cambridge, MA 02139, USA.  */
+
+#include <hurd/signal.h>
+#include <cthreads.h>
+#include "cthread_internals.h"
+
+int
+hurd_condition_wait_cancel (condition_t c, mutex_t m)
+{
+  /* This function will be called by hurd_thread_cancel while we are blocked
+     in the condition_wait.  We wake up all threads blocked on C,
+     so our thread will wake up and notice the cancellation flag.  */
+  void cancel_me (void)
+    {
+      condition_broadcast (c);
+    }
+  struct hurd_sigstate *ss = _hurd_self_sigstate ();
+  cproc_t p = cproc_self ();
+  int cancel;
+
+  p->state = CPROC_CONDWAIT | CPROC_SWITCHING;
+
+  /* Atomically enqueue our cproc on the condition variable's queue of
+     waiters, and mark our sigstate to indicate that `cancel_me' must be
+     called to wake us up.  We must hold the sigstate lock while acquiring
+     the condition variable's lock and tweaking it, so that
+     hurd_thread_cancel can never suspend us and then deadlock in
+     condition_broadcast waiting for the condition variable's lock.  */
+
+  spin_lock (&ss->lock);
+  spin_lock (&c->lock);
+  cancel = ss->cancel;
+  if (cancel)
+    /* We were cancelled before doing anything.  Don't block at all.  */
+    ss->cancel = 0;
+  else
+    {
+      /* Put us on the queue so that condition_broadcast will know to wake
+         us up.  */
+      cthread_queue_enq (&c->queue, p);
+      /* Tell hurd_thread_cancel how to unblock us.  */
+      ss->cancel_hook = &cancel_me;
+    }
+  spin_unlock (&c->lock);
+  spin_unlock (&ss->lock);
+
+  if (cancel)
+    {
+      /* Cancelled on entry.  Just leave the mutex locked.  */
+      m = NULL;
+      p->state = CPROC_RUNNING;
+    }
+  else
+    {
+      /* Now unlock the mutex and block until woken.  */
+
+#ifdef	WAIT_DEBUG
+      p->waiting_for = (char *)c;
+#endif	WAIT_DEBUG
+
+      mutex_unlock (m);
+
+      spin_lock (&p->lock);
+      if (p->state & CPROC_SWITCHING)
+	cproc_block ();
+      else
+	{
+	  /* We were woken up someplace before reacquiring P->lock.
+	     We can just continue on.  */
+	  p->state = CPROC_RUNNING;
+	  spin_unlock(&p->lock);
+	}
+
+#ifdef	WAIT_DEBUG
+      p->waiting_for = (char *)0;
+#endif	WAIT_DEBUG
+    }
+
+  spin_lock (&ss->lock);
+  /* Clear the hook, now that we are done blocking.  */
+  ss->cancel_hook = NULL;
+  /* Check the cancellation flag; we might have unblocked due to
+     cancellation rather than a normal condition_signal or
+     condition_broadcast (or we might have just happened to get cancelled
+     right after waking up).  */
+  cancel |= ss->cancel;
+  ss->cancel = 0;
+  spin_unlock (&ss->lock);
+
+  if (m)
+    /* Reacquire the mutex and return.  */
+    mutex_lock (m);
+
+  return cancel;
+}