[Qemu-devel] Re: [PATCH 07/21] add assertions on the owner of a QemuMutex

[Paolo Bonzini]

On 02/21/2011 10:50 AM, Jan Kiszka wrote:
> > >  +    /* An EDEADLOCK would arrive after we reset the owner.  So this
> > >  +       assert is for ease of debugging (it lets you see what is the
> > >  +       actual owner.  */
>
> Don't get this. Why do you want to avoid the proper error detection of
> pthread?

Because by the time you get to error_exit mutex->owner has been NULL-ed 
out already.  So it doesn't help to put a breakpoint on error_exit, you 
cannot find out which thread was the owner.

> But the assertions in the mutex layer
> are redundant for PTHREAD_MUTEX_ERRORCHECK - unless I'm missing
> something now.

Yes, but tracking the mutex's owner gives a bit more specific 
information when an error happens even for mutexes.  I removed them from 
lock/trylock, but for unlock it's already too late when the error happens.

Paolo