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 <[email protected]> --- drivers/base/power/domain.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c index cdd547bd67df8218..60e0309dd8dd0264 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(); } @@ -2183,6 +2191,7 @@ 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 +2227,13 @@ 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in Please read the FAQ at http://www.tux.org/lkml/
