Re: [PATCH v6 1/2 hurd] libirqhelp: Add library

[Samuel Thibault]

Samuel Thibault, le mar. 11 juil. 2023 10:20:45 +0200, a ecrit:
> Damien Zammit, le mar. 11 juil. 2023 07:58:39 +0000, a ecrit:
> > On 11/7/23 05:47, Samuel Thibault wrote:
> > > Damien Zammit, le lun. 10 juil. 2023 09:02:10 +0000, a ecrit:
> > >> +void
> > >> +irqhelp_wait_init(struct irq *irq)
> > >> +{
> > >> +  if (!irq)
> > >> +    {
> > >> +      log_error("cannot wait on this irq to be ready\n");
> > >> +      return;
> > >> +    }
> > >> +
> > >> +  sem_wait(&irq->sema);
> > >> +}
> > > 
> > > So, is this wait really necessary? Why?
> > 
> > Yes, without this wait, netdde.static crashes randomly on startup,
> > and if it doesn't crash the first time, it can be triggered to crash
> > by running ifdown then ifup.
> > 
> > I think the wait avoids a race.
> 
> Ok but we should really understand what race can exist, otherwise we
> don't really know why the code works.

(put another way, the sem_wait possibly only makes the race less
probable, without making it impossible)

Samuel