From 73e2232aa3253d77935112bfc218700f6a2f1000 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Wed, 7 Mar 2018 13:42:26 +0000 Subject: [PATCH] drm/i915: Only call tasklet_kill() on the first prepare_reset tasklet_kill() will spin waiting for the current tasklet to be executed. However, if tasklet_disable() has been called, then the tasklet is never executed but permanently put back onto the runlist until tasklet_enable() is called. Ergo, we cannot use tasklet_kill() inside a disable/enable pair. This is the case when we call set-wedge from inside i915_reset(), and another request was submitted to us concurrent to the reset. Fixes: 963ddd63c314 ("drm/i915: Suspend submission tasklets around wedging") Signed-off-by: Chris Wilson Cc: Mika Kuoppala Reviewed-by: Mika Kuoppala Link: https://patchwork.freedesktop.org/patch/msgid/20180307134226.25492-6-chris@chris-wilson.co.uk (cherry picked from commit 68ad361285a9cc73b259f59adbaafde196c15987) Signed-off-by: Joonas Lahtinen --- drivers/gpu/drm/i915/i915_gem.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 8d913d833ab9..0359d6f870b4 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2940,8 +2940,16 @@ i915_gem_reset_prepare_engine(struct intel_engine_cs *engine) * calling engine->init_hw() and also writing the ELSP. * Turning off the execlists->tasklet until the reset is over * prevents the race. + * + * Note that this needs to be a single atomic operation on the + * tasklet (flush existing tasks, prevent new tasks) to prevent + * a race between reset and set-wedged. It is not, so we do the best + * we can atm and make sure we don't lock the machine up in the more + * common case of recursively being called from set-wedged from inside + * i915_reset. */ - tasklet_kill(&engine->execlists.tasklet); + if (!atomic_read(&engine->execlists.tasklet.count)) + tasklet_kill(&engine->execlists.tasklet); tasklet_disable(&engine->execlists.tasklet); /*