From 32bdfac5462d777f35b00838893c4f87baf23efe Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Sun, 24 May 2009 21:15:07 +0200 Subject: PM: Do not hold dpm_list_mtx while disabling/enabling nonboot CPUs We shouldn't hold dpm_list_mtx while executing [disable|enable]_nonboot_cpus(), because theoretically this may lead to a deadlock as shown by the following example (provided by Johannes Berg): CPU 3 CPU 2 CPU 1 suspend/hibernate something: rtnl_lock() device_pm_lock() -> mutex_lock(&dpm_list_mtx) mutex_lock(&dpm_list_mtx) linkwatch_work -> rtnl_lock() disable_nonboot_cpus() -> flush CPU 3 workqueue Fortunately, device drivers are supposed to stop any activities that might lead to the registration of new device objects way before disable_nonboot_cpus() is called, so it shouldn't be necessary to hold dpm_list_mtx over the entire late part of device suspend and early part of device resume. Thus, during the late suspend and the early resume of devices acquire dpm_list_mtx only when dpm_list is going to be traversed and release it right after that. This patch is reported to fix the regressions tracked as http://bugzilla.kernel.org/show_bug.cgi?id=13245. Signed-off-by: Rafael J. Wysocki Acked-by: Alan Stern Reported-by: Miles Lane Tested-by: Ming Lei --- drivers/base/power/main.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'drivers/base/power/main.c') diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c index 69b4ddb7de3b..3e4bc699bc0f 100644 --- a/drivers/base/power/main.c +++ b/drivers/base/power/main.c @@ -357,6 +357,7 @@ static void dpm_power_up(pm_message_t state) { struct device *dev; + mutex_lock(&dpm_list_mtx); list_for_each_entry(dev, &dpm_list, power.entry) if (dev->power.status > DPM_OFF) { int error; @@ -366,6 +367,7 @@ static void dpm_power_up(pm_message_t state) if (error) pm_dev_err(dev, state, " early", error); } + mutex_unlock(&dpm_list_mtx); } /** @@ -614,6 +616,7 @@ int device_power_down(pm_message_t state) int error = 0; suspend_device_irqs(); + mutex_lock(&dpm_list_mtx); list_for_each_entry_reverse(dev, &dpm_list, power.entry) { error = suspend_device_noirq(dev, state); if (error) { @@ -622,6 +625,7 @@ int device_power_down(pm_message_t state) } dev->power.status = DPM_OFF_IRQ; } + mutex_unlock(&dpm_list_mtx); if (error) device_power_up(resume_event(state)); return error; -- cgit v1.2.3-59-g8ed1b