mutex held in a thread which is cancelled stays busy

[Konstantin Belousov]

On Tue, Aug 06, 2019 at 08:58:30PM -0400, Daniel Eischen wrote:
> 
> > On Aug 6, 2019, at 4:54 AM, Erich Dollansky <freebsd.ed.lists at sumeritec.com> wrote:
> > 
> > Hi,
> > 
> > for testing purpose, I did the following.
> > 
> > Start a thread, initialise a mutex in a global variable, lock the mutex
> > and wait in that thread.
> > 
> > Wait in the main program until above's thread waits and cancel it.
> > 
> > Clean up behind the cancelled thread but leave intentional the mutex
> > locked.
> > 
> > I would have expected now to get an error like 'EOWNERDEAD' doing
> > operations with that mutex. But I get 'EBUSY' as the error.
> 
> Are you initializing the mutex as a robust mutex, via pthread_mutexattr_setrobust()?  Are you using _lock() or _trylock()?
> 
Robust mutexes only have special properties on the process termination.
They behave same as the normal mutexes if the owning thread is terminated.

> For _trylock(), you only get EOWNERDEAD for robust mutexes.  It seems that you should get EOWNERDEAD for _lock() in this case, so if that's what you're doing, it sounds like it might be a bug.
> 
> --
> DE
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