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From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Linux PM <linux-pm@vger.kernel.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Tushar Nimkar <quic_tnimkar@quicinc.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Nitin Rawat <quic_nitirawa@quicinc.com>,
        Peter Wang <peter.wang@mediatek.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Ulf Hansson <ulf.hansson@linaro.org>
Subject: [PATCH v1 1/2] PM: runtime: Do not call __rpm_callback() from rpm_idle()
Date:   Fri, 02 Dec 2022 15:30:28 +0100
Message-ID: <4789678.31r3eYUQgx@kreacher>
In-Reply-To: <5627469.DvuYhMxLoT@kreacher>
References: <5627469.DvuYhMxLoT@kreacher>
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From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Calling __rpm_callback() from rpm_idle() after adding device links
support to the former is a clear mistake.

Not only it causes rpm_idle() to carry out unnecessary actions, but it
is also against the assumption regarding the stability of PM-runtime
status accross __rpm_callback() invocations, because rpm_suspend() and
rpm_resume() may run in parallel with __rpm_callback() when it is called
by rpm_idle() and the device's PM-runtime status can be updated by any
of them.

Fixes: 21d5c57b3726 ("PM / runtime: Use device links")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/base/power/runtime.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/base/power/runtime.c
===================================================================
--- linux-pm.orig/drivers/base/power/runtime.c
+++ linux-pm/drivers/base/power/runtime.c
@@ -484,7 +484,17 @@ static int rpm_idle(struct device *dev,
 
 	dev->power.idle_notification = true;
 
-	retval = __rpm_callback(callback, dev);
+	if (dev->power.irq_safe)
+		spin_unlock(&dev->power.lock);
+	else
+		spin_unlock_irq(&dev->power.lock);
+
+	retval = callback(dev);
+
+	if (dev->power.irq_safe)
+		spin_lock(&dev->power.lock);
+	else
+		spin_lock_irq(&dev->power.lock);
 
 	dev->power.idle_notification = false;
 	wake_up_all(&dev->power.wait_queue);