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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: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Geert Uytterhoeven 2015-06-26 11:14:14 +02:00 committed by Rafael J. Wysocki
parent d770e558e2
commit 93af5e9354
1 changed files with 11 additions and 2 deletions
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13
drivers/base/power/domain.c
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@ -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();
}