Author: thebeing
Date: Tue May 5 13:32:38 2015
New Revision: 38475
URL: http://svn.gna.org/viewcvs/gnustep?rev=38475&view=rev
Log:
Fix potential race condition when getting the top object without
removing it. (previously, we had a window between returning a peeked
pointer and retaining it where another thread might have been able to
pop and release the object).
Modified:
libs/performance/trunk/ChangeLog
libs/performance/trunk/GSFIFO.m
Modified: libs/performance/trunk/ChangeLog
URL:
http://svn.gna.org/viewcvs/gnustep/libs/performance/trunk/ChangeLog?rev=38475&r1=38474&r2=38475&view=diff
==============================================================================
--- libs/performance/trunk/ChangeLog (original)
+++ libs/performance/trunk/ChangeLog Tue May 5 13:32:38 2015
@@ -1,3 +1,7 @@
+2015-05-05 Niels Grewe <[email protected]>
+
+ * GSFIFO.m: Fix a potential race condition in -peekObject.
+
2015-05-05 Niels Grewe <[email protected]>
* GSFIFO.[hm]: Add methods to peek at the top/front object in the
Modified: libs/performance/trunk/GSFIFO.m
URL:
http://svn.gna.org/viewcvs/gnustep/libs/performance/trunk/GSFIFO.m?rev=38475&r1=38474&r2=38475&view=diff
==============================================================================
--- libs/performance/trunk/GSFIFO.m (original)
+++ libs/performance/trunk/GSFIFO.m Tue May 5 13:32:38 2015
@@ -216,6 +216,23 @@
return ptr;
}
+- (id) _cooperatingPeekObject
+{
+ [condition lock];
+ if ((_head - _tail) == 0)
+ {
+ // We do not need to signal the condition because
+ // nothing about the qeuue did change
+ [condition unlock];
+ return nil;
+ }
+ id obj =
+ [[(id<NSObject>)_items[_tail % _capacity] retain] autorelease];
+ [condition unlock];
+ return obj;
+}
+
+
- (void*) peek
{
if (condition != nil)
@@ -231,7 +248,15 @@
- (NSObject*) peekObject
{
- return [[(id<NSObject>)[self peek] retain] autorelease];
+ if (condition != nil)
+ {
+ return [self _cooperatingPeekObject];
+ }
+ if (_head - _tail == 0)
+ {
+ return nil;
+ }
+ return [[(id<NSObject>)_items[_tail % _capacity] retain] autorelease];
}
- (unsigned) _cooperatingPut: (void**)buf
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