linux-kernel - [PATCH] drm/vmwgfx: Replace schedule() with schedule

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Message-ID: <20250928054913.7871-1-opensource206@gmail.com>
Date: Sun, 28 Sep 2025 11:19:13 +0530
From: Pavan Bobba <opensource206@...il.com>
To: zack.rusin@...adcom.com,
	maarten.lankhorst@...ux.intel.com,
	mripard@...nel.org,
	tzimmermann@...e.de,
	airlied@...il.com,
	simona@...ll.ch
Cc: bcm-kernel-feedback-list@...adcom.com,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	Pavan Bobba <opensource206@...il.com>
Subject: [PATCH] drm/vmwgfx: Replace schedule() with schedule_hrtimeout() in fallback wait

Replace the open-coded polling with schedule() in vmw_fallback_wait()
by schedule_hrtimeout(). The old code wakes up at jiffy granularity and
leads to unnecessary CPU wakeups during fence waits.

schedule_hrtimeout() provides high-resolution sleep with finer control,
reducing CPU utilization without affecting fence correctness. For the
non-interruptible case, use schedule_timeout_uninterruptible().

Signed-off-by: Pavan Bobba <opensource206@...il.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_irq.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_irq.c b/drivers/gpu/drm/vmwgfx/vmwgfx_irq.c
index 05773eb394d3..64045b0efafc 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_irq.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_irq.c
@@ -202,16 +202,12 @@ int vmw_fallback_wait(struct vmw_private *dev_priv,
 		if (lazy)
 			schedule_timeout(1);
 		else if ((++count & 0x0F) == 0) {
-			/**
-			 * FIXME: Use schedule_hr_timeout here for
-			 * newer kernels and lower CPU utilization.
-			 */
-
-			__set_current_state(TASK_RUNNING);
-			schedule();
-			__set_current_state((interruptible) ?
-					    TASK_INTERRUPTIBLE :
-					    TASK_UNINTERRUPTIBLE);
+			ktime_t delta = ktime_set(0, NSEC_PER_MSEC);
+
+			if (interruptible)
+				schedule_hrtimeout(&delta, HRTIMER_MODE_REL);
+			else
+				schedule_timeout_uninterruptible(delta);
 		}
 		if (interruptible && signal_pending(current)) {
 			ret = -ERESTARTSYS;
-- 
2.43.0