> Date: Mon, 28 May 2018 12:24:22 +0200
> From: Mathieu - <naa...@poolp.org>
>
> Mark Kettenis wrote:
> > > Date: Mon, 28 May 2018 11:23:47 +0200
> > > From: Martin Pieuchot <m...@openbsd.org>
> > >
> > > As found by tb@ and visa@, `f_mtx' need to block interrupts as long as
> > > it can be taken w/ and w/o the KERNEL_LOCK(). Otherwise a deadlock is
> > > possible if an interrupt tries to grab the KERNEL_LOCK().
> > >
> > > I'm not switching to a rwlock because code paths are short, I don't
> > > want to introduce new sleeping points and in the long run we should
> > > be using SRPs or atomic operations for reference counts.
> > >
> > > ok?
> >
> > I suppose IPL_VM is the most sensible default for mutexes that need to
> > block all interrupts that might need the kernel lock.
> >
> > ok kettenis@
>
>
> Hello,
>
> Wouldn't IPL_MPFLOOR be more appropriate? After all mutexes are already
> raising the ipl level to IPL_MPFLOOR (expect for IPL_NONE and above).
The problem is that IPL_MPFLOOR doesn't exist on all platforms. Maybe
it should...
> > > Index: kern/kern_descrip.c
> > > ===================================================================
> > > RCS file: /cvs/src/sys/kern/kern_descrip.c,v
> > > retrieving revision 1.158
> > > diff -u -p -r1.158 kern_descrip.c
> > > --- kern/kern_descrip.c 8 May 2018 09:03:58 -0000 1.158
> > > +++ kern/kern_descrip.c 28 May 2018 09:23:31 -0000
> > > @@ -957,7 +957,11 @@ restart:
> > > */
> > > numfiles++;
> > > fp = pool_get(&file_pool, PR_WAITOK|PR_ZERO);
> > > - mtx_init(&fp->f_mtx, IPL_NONE);
> > > + /*
> > > + * We need to block interrupts as long as `f_mtx' is being taken
> > > + * with and without the KERNEL_LOCK().
> > > + */
> > > + mtx_init(&fp->f_mtx, IPL_VM);
> > > fp->f_iflags = FIF_LARVAL;
> > > if ((fq = p->p_fd->fd_ofiles[0]) != NULL) {
> > > LIST_INSERT_AFTER(fq, fp, f_list);
> > >
> > >
> >
>
