Re: [Valgrind-users] Helgrind 3.9.0: false positive with pthread_mutex_destroy

[Magnus R. <mag...@gm...>]

On 7 November 2013 18:21, Saurabh T <sa...@ho...> wrote:
> ----------------------------------------
>> From: fa...@kd...
>> To: val...@li...
>> CC: sa...@ho...
>> Subject: Re: [Valgrind-users] Helgrind 3.9.0: false positive with pthread_mutex_destroy
>> Date: Thu, 7 Nov 2013 17:25:57 +0100
>>
>> On Thursday 07 November 2013 16:22:56 Saurabh T wrote:
>>> Helgrind seems to be reporting false positive data race when
>>> pthread_mutex_destroy is called in a different thread from
>>> pthread_mutex_unlock. Unfortunately I cannot make a test case, sorry. But
>>> here's the relevant output:
>>> <snip>
>>
>> Can you prove that the destroy cannot happen during the unlock?
>
> Not without code of course, but I dont believe it can. It can however happen *before* the unlock. I believe this is allowed by the standard? The code is something like this:
> Thread 1:
>   locks
>   deletes
>   unlocks
> Thread 2:
>   locks
>   does_stuff
>   unlocks
>
> saurabh
>

That is most definitely wrong. Thread 1 destroys a locked mutex, and
according to http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_mutex_init.html
:
> Attempting to destroy a locked mutex results in undefined behavior.

BR
Magnus Reftel