Re: Trouble with mutex/cond destroy on WINCE 3.0

[Ross Johnson <rpj@ise.canberra.edu.au>]

Hi John,

Quite so. The first attempt to detect TryEnterCriticalSection did 
overlook this, and the additional check was added later. (Eventually 
Thomas Pfaff's reworking of the mutex routines eliminated the use of 
critical sections/Win32 mutexes, using the Interlocked routines and 
semaphores instead.)

However, pthreads-win32 doesn't currently apply the additional check 
on InterlockedCompareExchange and it hasn't been a problem AFAIK, 
but there's no reason not to add it as a rule.

Ross

Bossom, John wrote:
> Hi Ross,
> 
> It might not be enough to simply test for the existence of a
> function using dynamic loading on win32... Case in point:
> Win95 did not support TryEnterCriticalSection at all, whereas
> Win98 added the method, but did not implement it (i.e. returned
> function not supported if you called it...)
> 
> 
> -----Original Message-----
> From: Ross Johnson [mailto:rpj@ise.canberra.edu.au]
> Sent: Tuesday, February 25, 2003 6:16 PM
> To: Craig A. Vanderborgh
> Cc: pthreads-win32@sources.redhat.com
> Subject: Re: Trouble with mutex/cond destroy on WINCE 3.0
> 
> 
> 
> 
> Craig A. Vanderborgh wrote:
> 
> 
>>Hello All:
>>
>>I have just done a port of pthreads-win32 to our recently completed
>>arm-wince-pe GNU development environment.  This is different that what
>>others have been doing with pthreads-win32 in the following ways:
>> 
>>
> 
> Hi,
> 
> It looks like EBUSY is being returned by the call to 
> pthread_mutex_trylock() inside of pthread_mutex_destroy(), so I'm 
> wondering if there's a problem with InterlockedCompareExchange() on 
> arm-wince-pe.
> 
> What I think may be happening is this: pthread_win32_process_attach_np() 
> tries to detect if InterlockedCompareExchange() is supported by the 
> system. If this check fails for any reason then: on X86 systems, some 
> X86 specific assembler code is  called instead, everywhere it's needed 
> throughout the library via the function pointer 
> ptw32_interlocked_compare_exchange; on non-X86 systems the library 
> implementation of  InterlockedCompareExchange 
> (ptw32_InterlockedCompareExchange()) just returns 0, which will result 
> in EBUSY being returned by trylock() [for non recursive mutexes].
> 
> See:
>     pthread_mutex_destroy.c
>     pthread_mutex_trylock.c
>     pthread_win32_attach_detach_np.c
>     ptw32_InterlockedCompareExchange.c.
> 
> Questions:
> What error do you get if you apply pthread_mutex_trylock() to your mutex?
> Can you confirm that InterlockedCompareExchange() is supported AND being 
> detected?
> 
> BTW, if it turns out that you need an ARM specific 
> InterlockedCompareExchange(), then the following info may be useful:
> 
> http://www.google.com.au/search?q=cache:a3Px_EyvkM0C:lists.ximian.com/archiv
> es/public/mono-list/2002-September/002519.html+arm+InterlockedCompareExchang
> e&hl=en&ie=UTF-8
> 
> Regards.
> Ross
> 
> 
>>1. We are not using Visual C++ or EVC.  We have our own port of the GNU
>>toolchain (binutils-2.13.90 & gcc-3.2).
>>2. Except for a very few primitives from coredll.dll, we are not using
>>the Micro$oft runtime - we are using "newlib" instead.
>>
>>The porting work that was required seemed fairly straightforward and
>>affected mostly only header files in the end.  Unfortunately, the result
>>is not entirely working yet.  In particular, mutex/condvar destruction
>>is always returning "16" instead of "0" (EBUSY??).  Here is an example
>>program that shows the problem, along with the output:
>>
>>#include <pthread.h>
>>#include <errno.h>
>>
>>main(int argc, char *argv[])
>>{
>> int i, stat;
>> pthread_mutex_t mutex;
>> pthread_cond_t cond;
>>
>> pthread_win32_process_attach_np();
>> pthread_win32_thread_attach_np();
>> stat = pthread_mutex_init(&mutex, NULL);
>> printf("pthread_mutex_init returns %d, errno %d\n", stat, errno);
>>
>> stat = pthread_cond_init(&cond, NULL);
>> printf("pthread_cond_init returns %d, errno %d\n", stat, errno);
>>
>> stat = pthread_cond_destroy(&cond);
>> printf("pthread_cond_destroy returns %d, errno %d\n", stat, errno);
>>
>> stat = pthread_mutex_destroy(&mutex);
>> printf("pthread_mutex_destroy returns %d, errno %d\n", stat, errno);
>>
>> getchar();
>>}
>>
>>The output is thus:
>>thread_mutex_init returns 0, errno 0
>>pthread_cond_init returns 0, errno 0
>>pthread_cond_destroy returns 16, errno 0
>>pthread_mutex_destroy returns 16, errno 0
>>
>>Apparently "EBUSY" is returned when there are waiters on synchronization
>>objects.  Clearly that can't be the case here so there must be something
>>wrong with my port.  The question is - what??  Any ideas on where to
>>look or what to do would be vastly appreciated.
>>
>>TIA,
>>craig vanderborgh
>>voxware incorporated
>>
>>
>> 
>>
> 
> 
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