From: Dave Watson <davejwatson@fb.com>
Date: Tue, 7 Nov 2017 15:38:44 +0000 (-0800)
Subject: Remove incorrect DCHECKS
X-Git-Tag: v2017.11.13.00~26
X-Git-Url: http://plrg.eecs.uci.edu/git/?p=folly.git;a=commitdiff_plain;h=897877b826bf39211ef62a1172aa192efb54f4a2

Remove incorrect DCHECKS

Summary:
While the returned iterators are always 'valid' and can be read and iterated from,
they may still be concurrently erased from the map.  Current erase(iter) has DCHECKS that assert we can always
erase an iterator, but it may have already been removed.

Reviewed By: davidtgoldblatt

Differential Revision: D6221382

fbshipit-source-id: 70b21f53e2fc3daa126df4fb60bc5d3ecb253c71
---

diff --git a/folly/concurrency/detail/ConcurrentHashMap-detail.h b/folly/concurrency/detail/ConcurrentHashMap-detail.h
index ebbb44fc..6af07fee 100644
--- a/folly/concurrency/detail/ConcurrentHashMap-detail.h
+++ b/folly/concurrency/detail/ConcurrentHashMap-detail.h
@@ -543,7 +543,6 @@ class FOLLY_ALIGNED(64) ConcurrentHashMapSegment {
       node->release();
       return 1;
     }
-    DCHECK(!iter);
 
     return 0;
   }
@@ -555,8 +554,7 @@ class FOLLY_ALIGNED(64) ConcurrentHashMapSegment {
   // This is a small departure from standard stl containers: erase may
   // throw if hash or key_eq functions throw.
   void erase(Iterator& res, Iterator& pos) {
-    auto cnt = erase_internal(pos->first, &res);
-    DCHECK(cnt == 1);
+    erase_internal(pos->first, &res);
   }
 
   void clear() {
diff --git a/folly/concurrency/test/ConcurrentHashMapTest.cpp b/folly/concurrency/test/ConcurrentHashMapTest.cpp
index 32b3d8ae..824d37da 100644
--- a/folly/concurrency/test/ConcurrentHashMapTest.cpp
+++ b/folly/concurrency/test/ConcurrentHashMapTest.cpp
@@ -208,6 +208,14 @@ TEST(ConcurrentHashMap, MapIterateTest) {
   EXPECT_EQ(count, 2);
 }
 
+TEST(ConcurrentHashMap, EraseTest) {
+  ConcurrentHashMap<uint64_t, uint64_t> foomap(3);
+  foomap.insert(1, 0);
+  auto f1 = foomap.find(1);
+  EXPECT_EQ(1, foomap.erase(1));
+  foomap.erase(f1);
+}
+
 // TODO: hazptrs must support DeterministicSchedule
 
 #define Atom std::atomic // DeterministicAtomic