Commit 93af5e93 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Rafael J. Wysocki
Browse files

PM / Domains: Avoid infinite loops in attach/detach code 



If pm_genpd_{add,remove}_device() keeps on failing with -EAGAIN, we end
up with an infinite loop in genpd_dev_pm_{at,de}tach().

This may happen due to a genpd.prepared_count imbalance.  This is a bug
elsewhere, but it will result in a system lock up, possibly during
reboot of an otherwise functioning system.

To avoid this, put a limit on the maximum number of loop iterations,
using an exponential back-off mechanism.  If the limit is reached, the
operation will just fail.  An error message is already printed.

Signed-off-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent d770e558

drivers/base/power/domain.c

+11 −2
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
 * This file is released under the GPLv2.

 */



#include <linux/delay.h>

#include <linux/kernel.h>

#include <linux/io.h>

#include <linux/platform_device.h>
@@ -19,6 +20,8 @@ 
#include <linux/suspend.h>

#include <linux/export.h>



#define GENPD_RETRY_MAX_MS	250		/* Approximate */



#define GENPD_DEV_CALLBACK(genpd, type, callback, dev)		\

({								\

	type (*__routine)(struct device *__d); 			\
@@ -2131,6 +2134,7 @@ EXPORT_SYMBOL_GPL(of_genpd_get_from_provider); 
static void genpd_dev_pm_detach(struct device *dev, bool power_off)

{

	struct generic_pm_domain *pd;

	unsigned int i;

	int ret = 0;



	pd = pm_genpd_lookup_dev(dev);
@@ -2139,10 +2143,12 @@ static void genpd_dev_pm_detach(struct device *dev, bool power_off) 


	dev_dbg(dev, "removing from PM domain %s\n", pd->name);



	while (1) {

	for (i = 1; i < GENPD_RETRY_MAX_MS; i <<= 1) {

		ret = pm_genpd_remove_device(pd, dev);

		if (ret != -EAGAIN)

			break;



		mdelay(i);

		cond_resched();

	}
@@ -2183,6 +2189,7 @@ int genpd_dev_pm_attach(struct device *dev) 
{

	struct of_phandle_args pd_args;

	struct generic_pm_domain *pd;

	unsigned int i;

	int ret;



	if (!dev->of_node)
@@ -2218,10 +2225,12 @@ int genpd_dev_pm_attach(struct device *dev) 


	dev_dbg(dev, "adding to PM domain %s\n", pd->name);



	while (1) {

	for (i = 1; i < GENPD_RETRY_MAX_MS; i <<= 1) {

		ret = pm_genpd_add_device(pd, dev);

		if (ret != -EAGAIN)

			break;



		mdelay(i);

		cond_resched();

	}

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