From 8ea6bb8e4d47e07518e5dba4f5cb77e210f0df82 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Fri, 6 Mar 2020 15:46:47 +0000
Subject: drm/i915/gt: Close race between cacheline_retire and free
Git-commit: 8ea6bb8e4d47e07518e5dba4f5cb77e210f0df82
Patch-mainline: v5.6-rc6
References: bsc#1152489

If the cacheline may still be busy, atomically mark it for future
release, and only if we can determine that it will never be used again,
immediately free it.

Closes: https://gitlab.freedesktop.org/drm/intel/issues/1392
Fixes: ebece7539242 ("drm/i915: Keep timeline HWSP allocated until idle across the system")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: <stable@vger.kernel.org> # v5.2+
Link: https://patchwork.freedesktop.org/patch/msgid/20200306154647.3528345-1-chris@chris-wilson.co.uk
(cherry picked from commit 2d4bd971f5baa51418625f379a69f5d58b5a0450)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/i915/gt/intel_timeline.c |    8 ++++++--
 drivers/gpu/drm/i915/i915_active.c       |    6 ++++++
 drivers/gpu/drm/i915/i915_active.h       |    1 +
 3 files changed, 13 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/i915/gt/intel_timeline.c
+++ b/drivers/gpu/drm/i915/gt/intel_timeline.c
@@ -197,11 +197,15 @@ static void cacheline_release(struct int
 
 static void cacheline_free(struct intel_timeline_cacheline *cl)
 {
+	if (!i915_active_acquire_if_busy(&cl->active)) {
+		__idle_cacheline_free(cl);
+		return;
+	}
+
 	GEM_BUG_ON(ptr_test_bit(cl->vaddr, CACHELINE_FREE));
 	cl->vaddr = ptr_set_bit(cl->vaddr, CACHELINE_FREE);
 
-	if (i915_active_is_idle(&cl->active))
-		__idle_cacheline_free(cl);
+	i915_active_release(&cl->active);
 }
 
 int intel_timeline_init(struct intel_timeline *timeline,
--- a/drivers/gpu/drm/i915/i915_active.c
+++ b/drivers/gpu/drm/i915/i915_active.c
@@ -337,6 +337,12 @@ out:
 	return err;
 }
 
+bool i915_active_acquire_if_busy(struct i915_active *ref)
+{
+	debug_active_assert(ref);
+	return atomic_add_unless(&ref->count, 1, 0);
+}
+
 int i915_active_acquire(struct i915_active *ref)
 {
 	int err;
--- a/drivers/gpu/drm/i915/i915_active.h
+++ b/drivers/gpu/drm/i915/i915_active.h
@@ -381,6 +381,7 @@ int i915_request_await_active_request(st
 				      struct i915_active_request *active);
 
 int i915_active_acquire(struct i915_active *ref);
+bool i915_active_acquire_if_busy(struct i915_active *ref);
 void i915_active_release(struct i915_active *ref);
 void __i915_active_release_nested(struct i915_active *ref, int subclass);