mutex held in a thread which is cancelled stays busy

[Erich Dollansky]

Hi,

On Wed, 7 Aug 2019 10:10:02 +0300
Konstantin Belousov <kostikbel at gmail.com> wrote:

> 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.
> 
man says:

 [EOWNERDEAD]  The argument mutex points to a robust mutex and the
 previous owning thread terminated while holding the mutex lock.

Erich