[Intel-gfx] Regression on linux-next (next-20231130)

[Borah, Chaitanya Kumar]

Hello Johannes,

> -----Original Message-----
> From: Berg, Johannes <johannes.berg at intel.com>
> Sent: Monday, December 4, 2023 11:41 PM
> To: Borah, Chaitanya Kumar <chaitanya.kumar.borah at intel.com>
> Cc: intel-gfx at lists.freedesktop.org; Kurmi, Suresh Kumar
> <suresh.kumar.kurmi at intel.com>; Saarinen, Jani <jani.saarinen at intel.com>
> Subject: RE: Regression on linux-next (next-20231130)
> 
> Hi,
> 
> > [snip lockdep report]
> 
> > commit f4acfcd4deb158b96595250cc332901b282d15b0
> > Author: Johannes Berg johannes.berg at intel.com
> > Date:   Fri Nov 24 17:25:25 2023 +0100
> >
> >     debugfs: annotate debugfs handlers vs. removal with lockdep
> 
> Yes, obviously, since before that there was no lockdep class
> "debugfs:i915_pipe" 😊
> 
> > We also verified that if we revert the patch the issue is not seen.
> >
> > Could you please check why the patch causes this regression and
> > provide a fix if necessary?
> 
> First off, I already sent a revert, which should be included in the next -rc.
> Anyway this patch shouldn't have been included in the -rc cycle, I just
> erroneously included it with some bugfixes (that patch-wise had a
> dependency).
> 
> Secondly, we did find a false positive in another case, and yours seems to be
> the same or similar, due to seq_file not differentiating between the file
> instances.
> 
> That's a bit unfortunate, because we _did_ have actual deadlocks in wireless
> with debugfs_remove() being called on a file while holding a lock that the file
> also acquires, which can lead to a deadlock. Unless we differentiate seq_file
> instances though, there doesn't seem to be a good way to annotate that in
> debugfs, as this report and others show.

Thank you for the confirmation. We will wait for the revert to be included in linux-next.
Sounds like a useful addition. Hopefully, we can find a way for both of them to co-exist.

Regards

Chaitanya

> 
> johannes
> --