linux-kernel - [PATCH 7 v2] PM / Domains: Queue up power off work only if it is not pending

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Message-Id: <201107101429.26416.rjw@sisk.pl>
Date:	Sun, 10 Jul 2011 14:29:26 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Kevin Hilman <khilman@...com>,
	Alan Stern <stern@...land.harvard.edu>,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	Paul Walmsley <paul@...an.com>, Greg KH <gregkh@...e.de>,
	Magnus Damm <magnus.damm@...il.com>
Subject: [PATCH 7 v2] PM / Domains: Queue up power off work only if it is not pending

From: Rafael J. Wysocki <rjw@...k.pl>

In theory it is possible that pm_genpd_poweroff() for two different
subdomains of the same parent domain will attempt to queue up the
execution of pm_genpd_poweroff() for the parent twice in a row.  This
would lead to unpleasant consequences, so prevent it from happening
by checking if genpd->power_off_work is pending before attempting to
queue it up.

Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
---

One more patch to the "PM / Domains: Generic PM domains improvements" series,
the changelog should explain everything. :-)

Thanks,
Rafael

---
 drivers/base/power/domain.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

Index: linux-2.6/drivers/base/power/domain.c
===================================================================
--- linux-2.6.orig/drivers/base/power/domain.c
+++ linux-2.6/drivers/base/power/domain.c
@@ -213,6 +213,19 @@ static bool genpd_abort_poweroff(struct
 }
 
 /**
+ * genpd_queue_power_off_work - Queue up the execution of pm_genpd_poweroff().
+ * @genpd: PM domait to power off.
+ *
+ * Queue up the execution of pm_genpd_poweroff() unless it's already been done
+ * before.
+ */
+static void genpd_queue_power_off_work(struct generic_pm_domain *genpd)
+{
+	if (!work_pending(&genpd->power_off_work))
+		queue_work(pm_wq, &genpd->power_off_work);
+}
+
+/**
  * pm_genpd_poweroff - Remove power from a given PM domain.
  * @genpd: PM domain to power down.
  *
@@ -304,7 +317,7 @@ static int pm_genpd_poweroff(struct gene
 	if (parent) {
 		genpd_sd_counter_dec(parent);
 		if (parent->sd_count == 0)
-			queue_work(pm_wq, &parent->power_off_work);
+			genpd_queue_power_off_work(parent);
 
 		genpd_release_lock(parent);
 	}
--
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