[v2] Remaining BKL users, what to do
arnd at arndb.de
Mon Oct 18 08:42:06 PDT 2010
This is a update on the current progress for the BKL removal, reflecting
what is currently in linux-next.
Maybe we can briefly discuss this at the kernel summit to decide if we
want a quick death of the BKL, i.e. fixing/disabling/staging-out the
remaining users in 2.6.38 or rather leave them there indefinitely.
On Thursday 16 September 2010, Arnd Bergmann wrote:
> The big kernel lock is gone from almost all code in linux-next, this is
> the status of what I think will happen to the remaining users:
> Fixable, but needs someone with the hardware to test. Can probably be
> marked CONFIG_BROKEN_ON_SMP if nobody cares.
Still open, no good solution for this.
> drivers/media/video (V4L):
> Mauro is working on it, some drivers get moved to staging while the
> others get fixed. An easy workaround would be possible by adding
> per-driver mutexes, but Mauro wants to it properly by locking all
> the right places.
Progressing well, patches are being worked on.
> Probably not hard to fix, but needs someone to test it.
> adfs has only seen janitorial fixes for the last 5 years.
> Do we know of any users?
> Pretty much dead, replaced by autofs4. I'd suggest moving this
> to drivers/staging in 2.6.37 and letting it die there.
Now in staging.
> Coda seems to have an active community, but not all of their
> code is actually part of linux (pioctl!), while the last official
> release is missing many of the cleanups that were don in Linux.
> Not sure what to do, if someone is interested, the best way might
> be a fresh start with a merger of the mainline linux and the
> coda.cs.cmu.edu codebase in drivers/staging.
> Just removing the BKL without the Coda community seems like a heap
> of pointless work.
Jan Harkes showed interest, looks like this will get fixed eventually,
but probably not in time for 2.6.37.
> Uses the BKL in readdir and lookup, should be easy to fix. Christoph?
Still waiting for confirmation from Christoph Hellwig that the BKL
is not needed here. I can do the patch to remove it then.
> Looks fixable, if anyone cares. Maybe it's time for retirement in
> drivers/staging though. The web page only has a Link to the
> linux-2.2 version.
> Trond writes that he has someone working on BKL removal here.
Bryan Schumaker took care of this, looks like the locking is independent
of the fs/locks.c locking now, although it still uses the BKL internally.
I assume that this will get fixed as well, doesn't seem hard. As long
as lockd uses the BKL, both nfs and nfsd depend on the BKL implicitly.
> Patch is under discussion, blocked by work on fs/lockd currently.
No longer blocked now, both lockd and ceph can deal with this converted
to spinlocks. I will follow up with the final patch once they hit mainline.
> Should be fixable if Petr still cares about it. Otherwise suggest
> moving to drivers/staging if there are no users left.
Fixed by Petr Vandrovec.
> Should be easy to fix, there are only a few places in the code that
> use the BKL. Anders?
Anders Larsen volunteered.
> Last I heard this was considered obsolete. Should be move it to
> drivers/staging now?
Now in staging.
> Not completely trivial, but probably necessary to fix. Project web
> site is dead, I hope that Jan Kara can be motivated to fix it though.
Jan Kara volunteered to do it.
> Evgeniy Dushistov is maintaining this, I hope he can take care of
> getting rid of the BKL in UFS.
> Should be easy. Ingo? Steven?
> Can probably be saved from retirement in drivers/staging if the
> maintainers still care.
Samuel Ortiz fixed irda.
David Miller volunteered to do appletalk and ipx.
> Andrew Hendry has started working on it.
Patches have shown up in -next now, I suppose Andrew will finish it soon.
Out of the remaining modules, I guess i810/i830, adfs, hpfs and ufs might end
up not getting fixed at all, we can either mark them non-SMP or move them
to drivers/staging once all the others are done.
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