linux-kernel - [PATCH RFC] PM: runtime: Drop device usage only after remove is done

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Message-Id: <20230402103951.2510773-1-u.kleine-koenig@pengutronix.de>
Date:   Sun,  2 Apr 2023 12:39:51 +0200
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: [PATCH RFC] PM: runtime: Drop device usage only after remove is done

Many device drivers call one of the variants of pm_runtime_resume() in
their remove callback. So calling pm_runtime_put_sync() just before that
is ineffective as the suspend callback might just be called just to
resume the device directly afterwards again.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
---
Hello,

this is a theoretical issue that I noticed while doing some research how
pm-runtime works. Not sure it makes sense, so I marked it as RFC.

Best regards
Uwe

 drivers/base/dd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 8def2ba08a82..6beac141d3d2 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -1235,10 +1235,10 @@ static void __device_release_driver(struct device *dev, struct device *parent)
 
 		bus_notify(dev, BUS_NOTIFY_UNBIND_DRIVER);
 
-		pm_runtime_put_sync(dev);
-
 		device_remove(dev);
 
+		pm_runtime_put_sync(dev);
+
 		if (dev->bus && dev->bus->dma_cleanup)
 			dev->bus->dma_cleanup(dev);
 

base-commit: fe15c26ee26efa11741a7b632e9f23b01aca4cc6
-- 
2.39.2