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Date: Mon, 22 Jan 2024 10:57:48 +0100
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: Possiblly bug of cygwin1.dll
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On Jan 22 10:25, Corinna Vinschen via Cygwin wrote:
> On Jan 22 12:30, Takashi Yano via Cygwin wrote:
> > PATCH2: (for cygwin)
> > Avoid handle leak caused when non-static pthread_once_t is initialized
> > with PTHREAD_ONCE_INIT
> > diff --git a/winsup/cygwin/thread.cc b/winsup/cygwin/thread.cc
> > index 7bb4f9fc8..127569160 100644
> > --- a/winsup/cygwin/thread.cc
> > +++ b/winsup/cygwin/thread.cc
> > @@ -2060,6 +2060,9 @@ pthread::once (pthread_once_t *once_control, void (*init_routine) (void))
> >      {
> >        init_routine ();
> >        once_control->state = 1;
> > +      pthread_mutex_unlock (&once_control->mutex);
> > +      while (pthread_mutex_destroy (&once_control->mutex) == EBUSY);
> > +      return 0;
> >      }
> >    /* Here we must remove our cancellation handler */
> >    pthread_mutex_unlock (&once_control->mutex);
> 
> I see what you're doing here.  Wouldn't it be simpler, though, to do this?
> 
> diff --git a/winsup/cygwin/thread.cc b/winsup/cygwin/thread.cc
> index 7bb4f9fc8341..7ec3aace395d 100644
> --- a/winsup/cygwin/thread.cc
> +++ b/winsup/cygwin/thread.cc
> @@ -2063,6 +2063,7 @@ pthread::once (pthread_once_t *once_control, void (*init_routine) (void))
>      }
>    /* Here we must remove our cancellation handler */

Strange enough, this comment accompanies the code since its inception
in 2001.  It says explicitly "remove" the cancellation handler.
That sounds like the idea was right, just the programmer forgot about
it afterwards...

>    pthread_mutex_unlock (&once_control->mutex);
> +  while (pthread_mutex_destroy (&once_control->mutex) == EBUSY);
>    return 0;
>  }


Corinna