[Intel-gfx] [PATCH] drm/i915: Remove bogus locking check in the hangcheck code

[Daniel Vetter]

You can _never_ assert that a lock is not held, except in some very
restricted corner cases where it's guranteed that your code is running
single-threade (e.g. driver load before you've published any pointers
leading to that lock).

In addition the early return breaks a bunch of testcases since with
highly concurrent hangcheck stress tests the reset fails to work and
the test doesn't recover and time out.

This regression has been introduced in

commit b8d24a06568368076ebd5a858a011699a97bfa42
Author: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Date:   Wed Jan 28 17:03:14 2015 +0200

    drm/i915: Remove nested work in gpu error handling

Aside: It is possible to check whether a given task doesn't hold a
lock, but only when lockdep is enabled, using the lockdep_assert_held
stuff.

Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 drivers/gpu/drm/i915/i915_irq.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 53c5f9e39fe3..4145d95902f5 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -2612,9 +2612,6 @@ void i915_handle_error(struct drm_device *dev, bool wedged,
 	va_list args;
 	char error_msg[80];
 
-	if (WARN_ON(mutex_is_locked(&dev_priv->dev->struct_mutex)))
-		return;
-
 	va_start(args, fmt);
 	vscnprintf(error_msg, sizeof(error_msg), fmt, args);
 	va_end(args);
-- 
2.1.4