From 335828b3e367b4fc19221055f20bf4b7cee16c56 Mon Sep 17 00:00:00 2001
From: Vlad Brezae <brezaevlad@gmail.com>
Date: Thu, 2 Mar 2017 16:44:56 +0200
Subject: [PATCH] [sgen] Make sure workers don't have evacuating blocks on the
 free-lists

Double copying of an object during a collection is not allowed. If we allocate from an evacuating block this can happen.
---
 mono/sgen/sgen-marksweep.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/mono/sgen/sgen-marksweep.c b/mono/sgen/sgen-marksweep.c
index 450adcf3443..3492ff6058a 100644
--- a/mono/sgen/sgen-marksweep.c
+++ b/mono/sgen/sgen-marksweep.c
@@ -1555,6 +1555,25 @@ sgen_worker_clear_free_block_lists (WorkerData *worker)
 	}
 }
 
+static void
+sgen_worker_clear_free_block_lists_evac (WorkerData *worker)
+{
+	int i, j;
+
+	if (!worker->free_block_lists)
+		return;
+
+	for (i = 0; i < MS_BLOCK_TYPE_MAX; i++) {
+		for (j = 0; j < num_block_obj_sizes; j++) {
+			if (((MSBlockInfo***) worker->free_block_lists) [i][j])
+				SGEN_ASSERT (0, !((MSBlockInfo***) worker->free_block_lists) [i][j]->next_free, "Why do we have linked free blocks on the workers");
+
+			if (evacuate_block_obj_sizes [j])
+				((MSBlockInfo***) worker->free_block_lists) [i][j] = NULL;
+		}
+	}
+}
+
 static void
 sweep_start (void)
 {
@@ -2038,6 +2057,9 @@ major_start_major_collection (void)
 		sgen_evacuation_freelist_blocks (&free_block_lists [MS_BLOCK_FLAG_REFS][i], i);
 	}
 
+	/* We expect workers to have very few blocks on the freelist, just evacuate them */
+	sgen_workers_foreach (sgen_worker_clear_free_block_lists_evac);
+
 	if (lazy_sweep && concurrent_sweep) {
 		/*
 		 * sweep_blocks_job is created before sweep_finish, which we wait for above
-- 
2.25.1