From 93af5e93544328285a6f65f7d47bbea8979b28fb Mon Sep 17 00:00:00 2001 From: Geert Uytterhoeven Date: Fri, 26 Jun 2015 11:14:14 +0200 Subject: [PATCH] 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 Signed-off-by: Rafael J. Wysocki --- drivers/base/power/domain.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c index cdd547bd67df..0ee43c1056e0 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 #include #include #include @@ -19,6 +20,8 @@ #include #include +#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(); } -- 2.20.1