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>

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index a0c69f4a9652c2774f3574358d4600c4f2dacb5c..9db6b041a799f4345eb3bc2ed48d6bd6b96e2f04 100644 (file)
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -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);

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 12e38c213b70111c1b343af3b1b0bb4eaa99f829..508cbf31d43e3e026e960f649c6dd3b0a4c860a5 100644 (file)
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -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