[PATCH 2/2] PM / Domains: Avoid infinite loops in attach/detach code
From: Geert Uytterhoeven <geert+renesas@glider.be>
Date: 2015-06-18 10:22:58
Also in:
linux-sh, lkml
Subsystem:
driver core, kobjects, debugfs and sysfs, hibernation (aka software suspend, aka swsusp), power management core, suspend to ram, the rest · Maintainers:
Greg Kroah-Hartman, "Rafael J. Wysocki", Danilo Krummrich, Linus Torvalds
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,
including a simple 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>
---
drivers/base/power/domain.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index cdd547bd67df8218..aa06f60b98b8af35 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c@@ -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 +20,9 @@ #include <linux/suspend.h> #include <linux/export.h> +#define GENPD_RETRIES 20 +#define GENPD_DELAY_US 10 + #define GENPD_DEV_CALLBACK(genpd, type, callback, dev) \ ({ \ type (*__routine)(struct device *__d); \
@@ -2131,6 +2135,7 @@ 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 +2144,13 @@ 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 = 0; i < GENPD_RETRIES; i++) { ret = pm_genpd_remove_device(pd, dev); if (ret != -EAGAIN) break; + + if (i > GENPD_RETRIES / 2) + udelay(GENPD_DELAY_US); cond_resched(); }
@@ -2218,10 +2226,13 @@ int genpd_dev_pm_attach(struct device *dev) dev_dbg(dev, "adding to PM domain %s\n", pd->name); - while (1) { + for (i = 0; i < GENPD_RETRIES; i++) { ret = pm_genpd_add_device(pd, dev); if (ret != -EAGAIN) break; + + if (i > GENPD_RETRIES / 2) + udelay(GENPD_DELAY_US); cond_resched(); }
--
1.9.1