[PATCH] drm/i915/gvt: Fix unnecessary schedule timer when no vGPU exits

[Zhenyu Wang]

On 2020.03.03 12:45:01 +0800, Colin Xu wrote:
> Yes vgpu_lock is acquired after gvt->lock and vgpu_idr is in gvt domain so
> removing
> 
> it doesn't need vgpu_lock but need gvt->lock. And remove idr first can
> guarantee
> 
> that when vgpu destroy is on-going, other vgpu acquiring can exit asap so
> that no
> 
> race-condition with the cleanup tasks.
> 
> Thanks a lot for the fix!
> 
> Acked-by: Colin Xu <colin.xu at intel.com>

Thanks for the review! Rebase onto -fixes for 5.6.

From 777b1fe76c04302cb0ef996c3f92aab5a99a840b Mon Sep 17 00:00:00 2001
From: Zhenyu Wang <zhenyuw at linux.intel.com>
Date: Sat, 29 Feb 2020 13:54:45 +0800
Subject: [PATCH] drm/i915/gvt: Fix unnecessary schedule timer when no vGPU
 exits

From commit f25a49ab8ab9 ("drm/i915/gvt: Use vgpu_lock to protect per
vgpu access") the vgpu idr destroy is moved later than vgpu resource
destroy, then it would fail to stop timer for schedule policy clean
which to check vgpu idr for any left vGPU. So this trys to destroy
vgpu idr earlier.

Cc: Colin Xu <colin.xu at intel.com>
Fixes: f25a49ab8ab9 ("drm/i915/gvt: Use vgpu_lock to protect per vgpu access")
Acked-by: Colin Xu <colin.xu at intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw at linux.intel.com>
---
 drivers/gpu/drm/i915/gvt/vgpu.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/vgpu.c b/drivers/gpu/drm/i915/gvt/vgpu.c
index 487af6ea9972..345c2aa3b491 100644
--- a/drivers/gpu/drm/i915/gvt/vgpu.c
+++ b/drivers/gpu/drm/i915/gvt/vgpu.c
@@ -272,10 +272,17 @@ void intel_gvt_destroy_vgpu(struct intel_vgpu *vgpu)
 {
 	struct intel_gvt *gvt = vgpu->gvt;
 
-	mutex_lock(&vgpu->vgpu_lock);
-
 	WARN(vgpu->active, "vGPU is still active!\n");
 
+	/*
+	 * remove idr first so later clean can judge if need to stop
+	 * service if no active vgpu.
+	 */
+	mutex_lock(&gvt->lock);
+	idr_remove(&gvt->vgpu_idr, vgpu->id);
+	mutex_unlock(&gvt->lock);
+
+	mutex_lock(&vgpu->vgpu_lock);
 	intel_gvt_debugfs_remove_vgpu(vgpu);
 	intel_vgpu_clean_sched_policy(vgpu);
 	intel_vgpu_clean_submission(vgpu);
@@ -290,7 +297,6 @@ void intel_gvt_destroy_vgpu(struct intel_vgpu *vgpu)
 	mutex_unlock(&vgpu->vgpu_lock);
 
 	mutex_lock(&gvt->lock);
-	idr_remove(&gvt->vgpu_idr, vgpu->id);
 	if (idr_is_empty(&gvt->vgpu_idr))
 		intel_gvt_clean_irq(gvt);
 	intel_gvt_update_vgpu_types(gvt);
-- 
2.25.0.rc2


-- 
Open Source Technology Center, Intel ltd.

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