linux-kernel - [PATCH AUTOSEL 6.6 137/294] soc: apple: rtkit: Use high prio work queue

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Message-Id: <20250505225634.2688578-137-sashal@kernel.org>
Date: Mon,  5 May 2025 18:53:57 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Janne Grunau <j@...nau.net>,
	Alyssa Rosenzweig <alyssa@...enzweig.io>,
	Sven Peter <sven@...npeter.dev>,
	Sasha Levin <sashal@...nel.org>,
	asahi@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org
Subject: [PATCH AUTOSEL 6.6 137/294] soc: apple: rtkit: Use high prio work queue

From: Janne Grunau <j@...nau.net>

[ Upstream commit 22af2fac88fa5dbc310bfe7d0b66d4de3ac47305 ]

rtkit messages as communication with the DCP firmware for framebuffer
swaps or input events are time critical so use WQ_HIGHPRI to prevent
user space CPU load to increase latency.
With kwin_wayland 6's explicit sync mode user space load was able to
delay the IOMFB rtkit communication enough to miss vsync for surface
swaps. Minimal test scenario is constantly resizing a glxgears
Xwayland window.

Signed-off-by: Janne Grunau <j@...nau.net>
Reviewed-by: Alyssa Rosenzweig <alyssa@...enzweig.io>
Link: https://lore.kernel.org/r/20250226-apple-soc-misc-v2-3-c3ec37f9021b@svenpeter.dev
Signed-off-by: Sven Peter <sven@...npeter.dev>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/soc/apple/rtkit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/soc/apple/rtkit.c b/drivers/soc/apple/rtkit.c
index d9f19dc99da5e..b9c5281c445ee 100644
--- a/drivers/soc/apple/rtkit.c
+++ b/drivers/soc/apple/rtkit.c
@@ -744,7 +744,7 @@ struct apple_rtkit *apple_rtkit_init(struct device *dev, void *cookie,
 	rtk->mbox_cl.rx_callback = &apple_rtkit_rx;
 	rtk->mbox_cl.tx_done = &apple_rtkit_tx_done;
 
-	rtk->wq = alloc_ordered_workqueue("rtkit-%s", WQ_MEM_RECLAIM,
+	rtk->wq = alloc_ordered_workqueue("rtkit-%s", WQ_HIGHPRI | WQ_MEM_RECLAIM,
 					  dev_name(rtk->dev));
 	if (!rtk->wq) {
 		ret = -ENOMEM;
-- 
2.39.5