URL:
<http://savannah.gnu.org/bugs/?25102>
Summary: Contention for user defaults file lock can cause
deadlock
Project: GNUstep
Submitted by: lcampbel
Submitted on: Tue 16 Dec 2008 04:06:05 PM GMT
Category: Base/Foundation
Severity: 3 - Normal
Item Group: Bug
Status: None
Privacy: Public
Assigned to: None
Open/Closed: Open
Discussion Lock: Any
_______________________________________________________
Details:
In NSUserDefaults.m, there are several snippets like this one:
if (wasLocked == NO)
{
[self unlockDefaultsFile];
}
[_lock unlock];
The problem with this is that [self unlockDefaultsFile] calls
-[NSDistributedLock unlock], and if someone else has broken the lock (which
NSDistributedLock does after waiting a mere 5 seconds, hardcoded, which
isn't
enough when the system is heavily loaded), then -[NSDistributedLock unlock]
raises an exception. Since NSUserDefaults.m doesn't catch the exception, the
[_lock unlock] doesn't get called, and now you're stuck. This can happen when
you start up many gnustep-using processes at once.
The fix is to catch exceptions, unlock, and re-raise:
if (wasLocked == NO)
{
NS_DURING
[self unlockDefaultsFile];
NS_HANDLER
[_lock unlock];
[localException raise];
NS_ENDHANDLER
}
[_lock unlock];
_______________________________________________________
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<http://savannah.gnu.org/bugs/?25102>
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