Re: [PATCH AUTOSEL 6.6 15/32] debugfs: annotate debugfs handlers vs. removal with lockdep

[Sasha Levin]

On Mon, Dec 04, 2023 at 09:45:55PM +0100, Johannes Berg wrote:
> On Mon, 2023-12-04 at 20:32 +0000, Sasha Levin wrote:
> > From: Johannes Berg <johannes.berg@xxxxxxxxx>
> >
> > [ Upstream commit f4acfcd4deb158b96595250cc332901b282d15b0 ]
> >
> > When you take a lock in a debugfs handler but also try
> > to remove the debugfs file under that lock, things can
> > deadlock since the removal has to wait for all users
> > to finish.
> >
> > Add lockdep annotations in debugfs_file_get()/_put()
> > to catch such issues.
>
> This (and the previous patch) probably got picked up as dependencies for
> the locking things, but ... we reverted this.
>
> For 6.6, _maybe_ it's worth backporting this including the revert, but
> then I'd do that only when the revert landed to have them together. But
> then you should apply all the six patches listed below _and_ the revert,
> the set as here doesn't do anything useful.
>
> However ... given that debugfs is root-only, and you have to be
> reading/writing a file _while_ disconnecting and the file is removed,
> perhaps the whole thing isn't worth backporting at all.
>
>
>
> For 6.1 and earlier, I believe it's not needed at all, so please drop
> from there all of these:
>
> - debugfs: fix automount d_fsdata usage
> - debugfs: annotate debugfs handlers vs. removal with lockdep
> - debugfs: add API to allow debugfs operations cancellation
> - wifi: cfg80211: add locked debugfs wrappers
> - wifi: mac80211: use wiphy locked debugfs helpers for agg_status
> - wifi: mac80211: use wiphy locked debugfs for sdata/link
>
>
> I'd kind of think just dropping all of these completely makes more
> sense.

Will do, thanks!

--
Thanks,
Sasha