From f911e7234f83efe4842a453406e90ceac3cabd8e Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Thu, 15 Nov 2018 20:38:51 +0000 Subject: [PATCH] drm/i915/selftests: Workaround an issue with unused lockdep subclass MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit lockdep insists that if we give a lock a subclass, it must be used. Failure to do so triggers a self-consistency check when reading lockdep_stats: [ 49.902002] DEBUG_LOCKS_WARN_ON(debug_atomic_read(nr_unused_locks) != nr_unused) [ 49.902009] WARNING: CPU: 3 PID: 383 at kernel/locking/lockdep_proc.c:249 lockdep_stats_show+0x984/0xa10 [ 49.902026] Modules linked in: nls_ascii nls_cp437 vfat fat crct10dif_pclmul crc32_pclmul crc32c_intel aesni_intel aes_x86_64 crypto_simd cryptd glue_helper intel_cstate intel_uncore intel_rapl_perf intel_gtt efivars prime_numbers ahci libahci i2c_i801 video button efivarfs [last unloaded: drm_kms_helper] [ 49.902059] CPU: 3 PID: 383 Comm: cat Tainted: G U 4.20.0-rc2+ #304 [ 49.902068] Hardware name: Intel Corporation NUC7i5BNK/NUC7i5BNB, BIOS BNKBL357.86A.0052.2017.0918.1346 09/18/2017 [ 49.902079] RIP: 0010:lockdep_stats_show+0x984/0xa10 [ 49.902086] Code: 00 85 c0 0f 84 aa f8 ff ff 8b 05 77 37 e2 00 85 c0 0f 85 9c f8 ff ff 48 c7 c6 e0 57 bc 81 48 c7 c7 28 30 bb 81 e8 6b 77 fa ff <0f> 0b e9 82 f8 ff ff 48 c7 44 24 50 00 00 00 00 45 31 e4 31 db 31 [ 49.902103] RSP: 0018:ffffc90000247d58 EFLAGS: 00010292 [ 49.902110] RAX: 0000000000000044 RBX: 00000000000002f0 RCX: 0000000000000000 [ 49.902118] RDX: 0000000000000002 RSI: 0000000000000001 RDI: ffffffff810b3464 [ 49.902126] RBP: 0000000000000039 R08: 0000000000000002 R09: 0000000000000000 [ 49.902133] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000007ead [ 49.902141] R13: 0000000000000001 R14: ffff88884c021000 R15: 0000000000000097 [ 49.902150] FS: 00007fb347e66540(0000) GS:ffff88885e600000(0000) knlGS:0000000000000000 [ 49.902159] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 49.902165] CR2: 00007fb347aeb000 CR3: 00000008544bd005 CR4: 00000000001606e0 Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Michał Winiarski Cc: Matthew Auld Reviewed-by: Matthew Auld Link: https://patchwork.freedesktop.org/patch/msgid/20181115203851.25739-1-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_timeline.h | 19 +++++++++++++++++++ drivers/gpu/drm/i915/intel_engine_cs.c | 2 +- drivers/gpu/drm/i915/selftests/mock_engine.c | 2 +- 3 files changed, 21 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_timeline.h b/drivers/gpu/drm/i915/i915_timeline.h index a2c2c3ab5fb0ce..ebd71b487220ae 100644 --- a/drivers/gpu/drm/i915/i915_timeline.h +++ b/drivers/gpu/drm/i915/i915_timeline.h @@ -83,6 +83,25 @@ void i915_timeline_init(struct drm_i915_private *i915, const char *name); void i915_timeline_fini(struct i915_timeline *tl); +static inline void +i915_timeline_set_subclass(struct i915_timeline *timeline, + unsigned int subclass) +{ + lockdep_set_subclass(&timeline->lock, subclass); + + /* + * Due to an interesting quirk in lockdep's internal debug tracking, + * after setting a subclass we must ensure the lock is used. Otherwise, + * nr_unused_locks is incremented once too often. + */ +#ifdef CONFIG_DEBUG_LOCK_ALLOC + local_irq_disable(); + lock_map_acquire(&timeline->lock.dep_map); + lock_map_release(&timeline->lock.dep_map); + local_irq_enable(); +#endif +} + struct i915_timeline * i915_timeline_create(struct drm_i915_private *i915, const char *name); diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c index bc147d9e6c9227..885a901b6e1337 100644 --- a/drivers/gpu/drm/i915/intel_engine_cs.c +++ b/drivers/gpu/drm/i915/intel_engine_cs.c @@ -485,7 +485,7 @@ static void intel_engine_init_execlist(struct intel_engine_cs *engine) void intel_engine_setup_common(struct intel_engine_cs *engine) { i915_timeline_init(engine->i915, &engine->timeline, engine->name); - lockdep_set_subclass(&engine->timeline.lock, TIMELINE_ENGINE); + i915_timeline_set_subclass(&engine->timeline, TIMELINE_ENGINE); intel_engine_init_execlist(engine); intel_engine_init_hangcheck(engine); diff --git a/drivers/gpu/drm/i915/selftests/mock_engine.c b/drivers/gpu/drm/i915/selftests/mock_engine.c index 22a73da45ad58b..d0c44c18db429c 100644 --- a/drivers/gpu/drm/i915/selftests/mock_engine.c +++ b/drivers/gpu/drm/i915/selftests/mock_engine.c @@ -200,7 +200,7 @@ struct intel_engine_cs *mock_engine(struct drm_i915_private *i915, engine->base.submit_request = mock_submit_request; i915_timeline_init(i915, &engine->base.timeline, engine->base.name); - lockdep_set_subclass(&engine->base.timeline.lock, TIMELINE_ENGINE); + i915_timeline_set_subclass(&engine->base.timeline, TIMELINE_ENGINE); intel_engine_init_breadcrumbs(&engine->base); engine->base.breadcrumbs.mock = true; /* prevent touching HW for irqs */