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git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/base/trunk@31118 72102866-910b-0410-8b05-ffd578937521
This commit is contained in:
Richard Frith-MacDonald 2010-08-11 11:20:52 +00:00
parent a11aedbca8
commit 2e49dafc75
1 changed files with 17 additions and 9 deletions
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26
Source/NSTask.m
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@ -258,19 +258,27 @@ pty_slave(const char* name)
if (tasksLock == nil)
{
tasksLock = [NSRecursiveLock new];
/* The activeTasks map contains all task objects corresponding
* to running subtasks, and retains them until the subtask
/* The activeTasks map contains the NSTask objects corresponding
* to running subtasks, and retains them until the subprocess
* actually terminates.
* The previous implementation stored non-retained objects and
* the -finalize method removed them from the table, but this
* caused a thread safety issue event though table access was
* caused a thread safety issue even though table access was
* lock protected:
* If thread1 releases the task at the same time that the subtask
* dies and is 'reaped' by thread2, then there is a window such
* that thread1 can enter -dealloc while thread2 is retaining the
* object in an NSNotification. Then thread1 completes deallocation
* while thread2 performs the notification. Then thread2 tries to
* release the object ... but it's already deallocated.
* If thread t1 releases the task at the same time that the subtask
* dies and is 'reaped' by t2, then there is a window such
* that t1 can enter -dealloc while t2 is dealing with
* subprocess termination notification.
* So t1 completes deallocation while t2 performs
* the notification, and then t2 tries to release the object...
* t1: enter dealloc
* t2: lookup task in activeTasks and retain/autorelease it
* t2: create NSNotification (retaining task)
* t2: post notification
* t1: remove task from activeTasks
* t1: release memory occupied by task object.
* t2: complete notification ... attempt to release task object
* but it's already deallocated.
*/
activeTasks = NSCreateMapTable(NSIntMapKeyCallBacks,
NSObjectMapValueCallBacks, 0);