From: Daniel Vetter <daniel@ffwll.ch>
To: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org, stable@vger.kernel.org,
"Nikunj A. Dadhania" <nikunj.dadhania@linux.intel.com>,
dri-devel@lists.freedesktop.org,
Daniel Vetter <daniel.vetter@intel.com>,
Chris Wilson <chris@chris-wilson.co.uk>
Subject: Re: [Intel-gfx] [PATCH 3/3] drm/i915/gem: Serialise debugfs i915_gem_objects with ctx->mutex
Date: Wed, 16 Sep 2020 09:42:30 +0200 [thread overview]
Message-ID: <20200916074230.GS438822@phenom.ffwll.local> (raw)
In-Reply-To: <5e7f2c00-c72e-46ff-defe-404b5a847a02@linux.intel.com>
On Mon, Sep 14, 2020 at 05:45:09PM +0100, Tvrtko Ursulin wrote:
>
> On 23/07/2020 18:21, Chris Wilson wrote:
> > Since the debugfs may peek into the GEM contexts as the corresponding
> > client/fd is being closed, we may try and follow a dangling pointer.
> > However, the context closure itself is serialised with the ctx->mutex,
> > so if we hold that mutex as we inspect the state coupled in the context,
> > we know the pointers within the context are stable and will remain valid
> > as we inspect their tables.
> >
> > Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: CQ Tang <cq.tang@intel.com>
> > Cc: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: stable@vger.kernel.org
> > ---
> > drivers/gpu/drm/i915/i915_debugfs.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> > index 784219962193..ea469168cd44 100644
> > --- a/drivers/gpu/drm/i915/i915_debugfs.c
> > +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> > @@ -326,6 +326,7 @@ static void print_context_stats(struct seq_file *m,
> > }
> > i915_gem_context_unlock_engines(ctx);
> > + mutex_lock(&ctx->mutex);
> > if (!IS_ERR_OR_NULL(ctx->file_priv)) {
> > struct file_stats stats = {
> > .vm = rcu_access_pointer(ctx->vm),
> > @@ -346,6 +347,7 @@ static void print_context_stats(struct seq_file *m,
> > print_file_stats(m, name, stats);
> > }
> > + mutex_unlock(&ctx->mutex);
> > spin_lock(&i915->gem.contexts.lock);
> > list_safe_reset_next(ctx, cn, link);
> >
>
> Hm this apparently never got it's r-b and so got re-discovered in the field.
> +Nikunj
>
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
I'm not super thrilled about patch 1 in this, for debugfs imo better to
wrangle this in the driver. And without patch 1 and 2 this wont fix a
whole lot.
-Daniel
>
> Regards,
>
> Tvrtko
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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next prev parent reply other threads:[~2020-09-16 7:42 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-23 17:21 [PATCH 1/3] drm: Restore driver.preclose() for all to use Chris Wilson
2020-07-23 17:21 ` [PATCH 2/3] drm/i915/gem: Move context decoupling from postclose to preclose Chris Wilson
2020-07-23 17:44 ` Tang, CQ
2020-07-23 17:48 ` Chris Wilson
2020-07-23 17:21 ` [PATCH 3/3] drm/i915/gem: Serialise debugfs i915_gem_objects with ctx->mutex Chris Wilson
2020-07-27 21:24 ` Sasha Levin
2020-09-14 16:45 ` [Intel-gfx] " Tvrtko Ursulin
2020-09-16 7:42 ` Daniel Vetter [this message]
2020-09-16 8:27 ` Tvrtko Ursulin
2020-07-27 19:32 ` [PATCH 1/3] drm: Restore driver.preclose() for all to use Daniel Vetter
2020-07-27 20:11 ` Tang, CQ
2020-07-28 16:27 ` Chris Wilson
2020-07-29 15:09 ` Tang, CQ
2020-07-27 21:24 ` Sasha Levin
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