Commit 05df49e7 authored Mar 12, 2017 by Daniel Vetter

drm/i915: annote drop_caches debugfs interface with lockdep



The trouble we have is that we can't really test all the shrinker
recursion stuff exhaustively in BAT because any kind of thrashing
stress test just takes too long.

But that leaves a really big gap open, since shrinker recursions are
one of the most annoying bugs. Now lockdep already has support for
checking allocation deadlocks:

- Direct reclaim paths are marked up with
  lockdep_set_current_reclaim_state() and
  lockdep_clear_current_reclaim_state().

- Any allocation paths are marked with lockdep_trace_alloc().

If we simply mark up our debugfs with the reclaim annotations, any
code and locks taken in there will automatically complete the picture
with any allocation paths we already have, as long as we have a simple
testcase in BAT which throws out a few objects using this interface.
Not stress test or thrashing needed at all.

v2: Need to EXPORT_SYMBOL_GPL to make it compile as a module.

v3: Fixup rebase fail (spotted by Chris).

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170312205340.16202-1-daniel.vetter@ffwll.ch


Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

parent bb1d1329

drivers/gpu/drm/i915/i915_debugfs.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -4261,6 +4261,7 @@ i915_drop_caches_set(void *data, u64 val)
		if (val & (DROP_RETIRE \| DROP_ACTIVE))
		i915_gem_retire_requests(dev_priv);

		lockdep_set_current_reclaim_state(GFP_KERNEL);
		if (val & DROP_BOUND)
		i915_gem_shrink(dev_priv, LONG_MAX, I915_SHRINK_BOUND);

		@@ -4269,6 +4270,7 @@ i915_drop_caches_set(void *data, u64 val)

		if (val & DROP_SHRINK_ALL)
		i915_gem_shrink_all(dev_priv);
		lockdep_clear_current_reclaim_state();

		unlock:
		mutex_unlock(&dev->struct_mutex);

kernel/locking/lockdep.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -3856,11 +3856,13 @@ void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
		{
		current->lockdep_reclaim_gfp = gfp_mask;
		}
		EXPORT_SYMBOL_GPL(lockdep_set_current_reclaim_state);

		void lockdep_clear_current_reclaim_state(void)
		{
		current->lockdep_reclaim_gfp = 0;
		}
		EXPORT_SYMBOL_GPL(lockdep_clear_current_reclaim_state);

		#ifdef CONFIG_LOCK_STAT
		static int

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