linux-kernel - Re: [Intel-gfx] [PATCH 3/3] drm/i915: use might_lock_nested in get

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Date:   Tue, 05 Nov 2019 11:02:28 +0200
From:   Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
To:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [Intel-gfx] [PATCH 3/3] drm/i915: use might_lock_nested in get_pages
 annotation

Quoting Daniel Vetter (2019-11-04 19:37:20)
> So strictly speaking the existing annotation is also ok, because we
> have a chain of
> 
> obj->mm.lock#I915_MM_GET_PAGES -> fs_reclaim -> obj->mm.lock
> 
> (the shrinker cannot get at an object while we're in get_pages, hence
> this is safe). But it's confusing, so try to take the right subclass
> of the lock.
> 
> This does a bit reduce our lockdep based checking, but then it's also
> less fragile, in case we ever change the nesting around.
> 
> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Will Deacon <will@...nel.org>
> Cc: linux-kernel@...r.kernel.org

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>

Regards, Joonas