From 984745b074c186f6058730087a4fc8156240ec76 Mon Sep 17 00:00:00 2001
From: Ben Gamari <ben@smart-cactus.org>
Date: Wed, 31 Jul 2019 22:29:13 -0400
Subject: nonmoving: Upper-bound time we hold SM_MUTEX for during sweep

---
 rts/sm/NonMovingSweep.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

(limited to 'rts/sm')

diff --git a/rts/sm/NonMovingSweep.c b/rts/sm/NonMovingSweep.c
index 31a9041880..cf5fcd70d7 100644
--- a/rts/sm/NonMovingSweep.c
+++ b/rts/sm/NonMovingSweep.c
@@ -293,9 +293,33 @@ void nonmovingSweepMutLists()
     }
 }
 
+/* A variant of freeChain_lock that will only hold the lock for at most max_dur
+ * freed blocks to ensure that we don't starve other lock users (e.g. the
+ * mutator).
+ */
+static void freeChain_lock_max(bdescr *bd, int max_dur)
+{
+  ACQUIRE_SM_LOCK;
+  bdescr *next_bd;
+  int i = 0;
+  while (bd != NULL) {
+    next_bd = bd->link;
+    freeGroup(bd);
+    bd = next_bd;
+    if (i == max_dur) {
+        RELEASE_SM_LOCK;
+        yieldThread();
+        ACQUIRE_SM_LOCK;
+        i = 0;
+    }
+    i++;
+  }
+  RELEASE_SM_LOCK;
+}
+
 void nonmovingSweepLargeObjects()
 {
-    freeChain_lock(nonmoving_large_objects);
+    freeChain_lock_max(nonmoving_large_objects, 10000);
     nonmoving_large_objects = nonmoving_marked_large_objects;
     n_nonmoving_large_blocks = n_nonmoving_marked_large_blocks;
     nonmoving_marked_large_objects = NULL;
-- 
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