Re: Problems with GSLazyRecursiveLock on MOSX

[David Ayers]

Philip Mötteli wrote:
> Hi
>
>
> I try to use GSW on MOSX. The moment I access the first page, there's 
> some initializing stuff and then a GSLazyRecursiveLock gets deallocated, 
> which in turn calls [super deallocate] and the super class crashes 
> somewhere in pthread_mutex_destroy. I have the backtrace attached. The 
> output from the program doesn't help me a lot:
[snip]
> I think the backtrace could help more:
>
> #0  0xffff8264 in __spin_lock ()
> #1  0x90014058 in pthread_mutex_destroy ()
> #2  0x90a22bdc in -[NSRecursiveLock dealloc] ()
> #3  0x0021195c in -[     dealloc] (self=0x6d2690, _cmd=0x90870b34) at 
> GSLock.m:228
> #4  0x00211a64 in -[GSLazyRecursiveLock init] (self=0x6d2690, 
> _cmd=0x9083ed94) at GSLock.m:241

Hmm.  The application seems to be in a multi threaded state already, 
when +[GSRecursiveLazy newLockAt:] is being called for the first time. 
That's why we try to RELEASE(self) the new GSRecursiveLock and then we 
would replace self with a NSRecursiveLock.  This is the recursive lock 
uses in GSCategories.m internally to guard newLockAt: calls.  It's being 
setup during an +initialize so that it's done under the ObjC runtime's 
internal lock.  It seems that Foundation's dealloc implementation of 
NSLock makes assumptions about the runtimes lock.

One solution could be changing Source/Additions/GSCategories.m 
_GSLockInitializer to initialize the local_lock with an NSRecursiveLock 
(this would make all calls to newLockAt: slower, but I'm not sure if 
that's significant).  This would "work around" the problem by not 
creating a GSLazy*Lock during +initialize.

Another would be to change Source/Additions/GSLock.m 
[GSLazy(Recursive)Lock] to AUTORELEASE(self) instead of RELEASE(self). 
This could make GSLazy*Lock safe(r) wrt +initialize.

I'm leaning toward the latter but I'm open to suggestions.

Cheers,
David



> #5  0x0020a038 in +[_GSLockInitializer initialize] (self=0x23778c, 
> _cmd=0x9083ebbc) at GSCategories.m:1161
> #6  0x908329e0 in class_initialize ()
> #7  0x90831524 in _class_lookupMethodAndLoadCache ()
> #8  0x90831298 in objc_msgSend ()
> #9  0x0020a370 in newLockAt (self=0x23793c, _cmd=0x401428, 
> location=0x402260) at GSCategories.m:1181
> #10 0x0020a0cc in +[NSRecursiveLock(GSCategories) newLockAt:] 
> (self=0x23793c, _cmd=0x401428, location=0x402260) at GSCategories.m:1254
> #11 0x003f2568 in GSUseStrictWO451Compatibility (key=0x0) at 
> EONSAddOns.m:71