From 031fd45d17d4887fdd437ae73608e55e76660781 Mon Sep 17 00:00:00 2001
From: Rickard Green <rickard@erlang.org>
Date: Fri, 8 Apr 2011 14:50:26 +0200
Subject: Avoid scheduling of processes being garbage collected by others

---
 erts/emulator/beam/erl_process.c | 66 ++++++++++++++++++++++++++++++----------
 1 file changed, 50 insertions(+), 16 deletions(-)

(limited to 'erts/emulator/beam/erl_process.c')

diff --git a/erts/emulator/beam/erl_process.c b/erts/emulator/beam/erl_process.c
index 21625921d5..8c3d21b98f 100644
--- a/erts/emulator/beam/erl_process.c
+++ b/erts/emulator/beam/erl_process.c
@@ -3889,21 +3889,9 @@ handle_pend_sync_suspend(Process *suspendee,
     }
 }
 
-/*
- * Like erts_pid2proc() but:
- *
- * * At least ERTS_PROC_LOCK_MAIN have to be held on c_p.
- * * At least ERTS_PROC_LOCK_MAIN have to be taken on pid.
- * * It also waits for proc to be in a state != running and garbing.
- * * If ERTS_PROC_LOCK_BUSY is returned, the calling process has to
- *   yield (ERTS_BIF_YIELD[0-3]()). c_p might in this case have been
- *   suspended.
- */
-
-
-Process *
-erts_pid2proc_not_running(Process *c_p, ErtsProcLocks c_p_locks,
-			  Eterm pid, ErtsProcLocks pid_locks)
+static Process *
+pid2proc_not_running(Process *c_p, ErtsProcLocks c_p_locks,
+		     Eterm pid, ErtsProcLocks pid_locks, int suspend)
 {
     Process *rp;
     int unlock_c_p_status;
@@ -3930,7 +3918,7 @@ erts_pid2proc_not_running(Process *c_p, ErtsProcLocks c_p_locks,
 	c_p->suspendee = NIL;
 	ASSERT(c_p->flags & F_P2PNR_RESCHED);
 	c_p->flags &= ~F_P2PNR_RESCHED;
-	if (rp)
+	if (!suspend && rp)
 	    resume_process(rp);
     }
     else {
@@ -3994,6 +3982,8 @@ erts_pid2proc_not_running(Process *c_p, ErtsProcLocks c_p_locks,
 	    }
 
 	    /* rp is not running and we got the locks we want... */
+	    if (suspend)
+		suspend_process(rp_rq, rp);
 	}
 	erts_smp_runqs_unlock(cp_rq, rp_rq);
     }
@@ -4006,6 +3996,35 @@ erts_pid2proc_not_running(Process *c_p, ErtsProcLocks c_p_locks,
     return rp;
 }
 
+
+/*
+ * Like erts_pid2proc() but:
+ *
+ * * At least ERTS_PROC_LOCK_MAIN have to be held on c_p.
+ * * At least ERTS_PROC_LOCK_MAIN have to be taken on pid.
+ * * It also waits for proc to be in a state != running and garbing.
+ * * If ERTS_PROC_LOCK_BUSY is returned, the calling process has to
+ *   yield (ERTS_BIF_YIELD[0-3]()). c_p might in this case have been
+ *   suspended.
+ */
+Process *
+erts_pid2proc_not_running(Process *c_p, ErtsProcLocks c_p_locks,
+			  Eterm pid, ErtsProcLocks pid_locks)
+{
+    return pid2proc_not_running(c_p, c_p_locks, pid, pid_locks, 0);
+}
+
+/*
+ * Like erts_pid2proc_not_running(), but hands over the process
+ * in a suspended state unless (c_p is looked up).
+ */
+Process *
+erts_pid2proc_suspend(Process *c_p, ErtsProcLocks c_p_locks,
+		      Eterm pid, ErtsProcLocks pid_locks)
+{
+    return pid2proc_not_running(c_p, c_p_locks, pid, pid_locks, 1);
+}
+
 /*
  * erts_pid2proc_nropt() is normally the same as
  * erts_pid2proc_not_running(). However it is only
@@ -4119,6 +4138,21 @@ handle_pend_bif_async_suspend(Process *suspendee,
     }
 }
 
+#else
+
+/*
+ * Non-smp version of erts_pid2proc_suspend().
+ */
+Process *
+erts_pid2proc_suspend(Process *c_p, ErtsProcLocks c_p_locks,
+		      Eterm pid, ErtsProcLocks pid_locks)
+{
+    Process *rp = erts_pid2proc(c_p, c_p_locks, pid, pid_locks);
+    if (rp)
+	erts_suspend(rp, pid_locks, NULL);
+    return rp;
+}
+
 #endif /* ERTS_SMP */
 
 /*
-- 
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