On Mon, Apr 18, 2005 at 10:56:57AM -0500, Tom Zanussi wrote:
> Kingsley Cheung writes:
> > On Wed, Mar 23, 2005 at 08:02:54PM +1100, [email protected] wrote:
> > > Hi
> > >
> > > I'm using relayfs to relay data from a kernel module to user space on
> > > a SuSE 2.6.5 kernel. I'm not absolutely sure what version of relayfs
> > > has been back ported to it.
> >
> > Hi Tom,
> >
> > Could you please have a look at the following use of relay_reset() in
> > a kernel module as follows (compiled against pre-redux relayfs):
(snip)
> > Is that legitimate? The reason I ask is because I've been seeing
>
> Yes, you should be able to reset the channel here, since at that point
> it's been closed.
>
> > garbled oopses with keventd and I've narrowed it to two things:
> >
> > 1) Inadequate locking on my part in the kernel module, which I have
> > addressed separately.
> >
> > 2) A race with relay_reset() and keventd, which is probably of
> > interest to you if you're still maintaining the pre-redux patches.
> >
> > The race is due to the use of INIT_WORK in _reset_relay():
> >
> > INIT_WORK(&rchan->wake_readers, NULL, NULL);
> > INIT_WORK(&rchan->wake_writers, NULL, NULL);
> >
> > However, at the time relay_reset() is called, it is possible that
> > these work structures are still being used by keventd when under heavy
> > loads. The workaround I've used to fix this is to call
> > flush_scheduled_work() before calling reset_relay() in the kernel
> > module. Perhaps that needs to be called in relay_reset() or
> > _relay_reset()?
Tom,
Thanks for the prompt response.
> Yes, flush_scheduled_work() should probably be called from
> __relay_reset() - thanks for catching this and suggesting the fix.
My pleasure.
> BTW, I've updated the old relayfs patch with your previous fixes and
> ported it to 2.6.11 - it hasn't appeared yet on the opersys website,
> so let me know if you want it and I'll send it, or I can just send you
> a new version after I make these changes...
Ok, good to hear. I've been using the old patch against an earlier
version of the kernel, so I've no rush for a patch against 2.6.11 -
you can take your time with these new changes :)
> > As well I'm not sure about the uses of INIT_WORK in
> > _relay_realloc_buffer() and relay_release() - perhaps they need
> > attention too. I understand, however, that flush_schedule_work()
>
> I'll take a look at this too - looks like there might be a potential
> problem if a channel was closed while a resize was in progress. I
> don't think anyone's ever actually used resizing, but it should be
> fixed nonetheless.
>
> Thanks,
>
> Tom
>
Right. Thanks again for looking at it.
--
Kingsley
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
