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 <rjw@sisk.pl>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Miles Lane <miles.lane@gmail.com>
Tested-by: Ming Lei <tom.leiming@gmail.com>

diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 69b4ddb..3e4bc69 100644 (file)
--- 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;

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 5a758c6..e498377 100644 (file)
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1451,7 +1451,6 @@ int kernel_kexec(void)
                error = device_suspend(PMSG_FREEZE);
                if (error)
                        goto Resume_console;
-               device_pm_lock();
                /* At this point, device_suspend() has been called,
                 * but *not* device_power_down(). We *must*
                 * device_power_down() now.  Otherwise, drivers for
@@ -1489,7 +1488,6 @@ int kernel_kexec(void)
                enable_nonboot_cpus();
                device_power_up(PMSG_RESTORE);
  Resume_devices:
-               device_pm_unlock();
                device_resume(PMSG_RESTORE);
  Resume_console:
                resume_console();

diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index b0dc9e7..5cb080e 100644 (file)
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -215,8 +215,6 @@ static int create_image(int platform_mode)
        if (error)
                return error;
 
-       device_pm_lock();
-
        /* At this point, device_suspend() has been called, but *not*
         * device_power_down(). We *must* call device_power_down() now.
         * Otherwise, drivers for some devices (e.g. interrupt controllers)
@@ -227,7 +225,7 @@ static int create_image(int platform_mode)
        if (error) {
                printk(KERN_ERR "PM: Some devices failed to power down, "
                        "aborting hibernation\n");
-               goto Unlock;
+               return error;
        }
 
        error = platform_pre_snapshot(platform_mode);
@@ -280,9 +278,6 @@ static int create_image(int platform_mode)
        device_power_up(in_suspend ?
                (error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE);
 
- Unlock:
-       device_pm_unlock();
-
        return error;
 }
 
@@ -344,13 +339,11 @@ static int resume_target_kernel(bool platform_mode)
 {
        int error;
 
-       device_pm_lock();
-
        error = device_power_down(PMSG_QUIESCE);
        if (error) {
                printk(KERN_ERR "PM: Some devices failed to power down, "
                        "aborting resume\n");
-               goto Unlock;
+               return error;
        }
 
        error = platform_pre_restore(platform_mode);
@@ -403,9 +396,6 @@ static int resume_target_kernel(bool platform_mode)
 
        device_power_up(PMSG_RECOVER);
 
- Unlock:
-       device_pm_unlock();
-
        return error;
 }
 
@@ -464,11 +454,9 @@ int hibernation_platform_enter(void)
                goto Resume_devices;
        }
 
-       device_pm_lock();
-
        error = device_power_down(PMSG_HIBERNATE);
        if (error)
-               goto Unlock;
+               goto Resume_devices;
 
        error = hibernation_ops->prepare();
        if (error)
@@ -493,9 +481,6 @@ int hibernation_platform_enter(void)
 
        device_power_up(PMSG_RESTORE);
 
- Unlock:
-       device_pm_unlock();
-
  Resume_devices:
        entering_platform_hibernation = false;
        device_resume(PMSG_RESTORE);

diff --git a/kernel/power/main.c b/kernel/power/main.c
index f99ed6a..8680282 100644 (file)
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -289,12 +289,10 @@ static int suspend_enter(suspend_state_t state)
 {
        int error;
 
-       device_pm_lock();
-
        if (suspend_ops->prepare) {
                error = suspend_ops->prepare();
                if (error)
-                       goto Done;
+                       return error;
        }
 
        error = device_power_down(PMSG_SUSPEND);
@@ -343,9 +341,6 @@ static int suspend_enter(suspend_state_t state)
        if (suspend_ops->finish)
                suspend_ops->finish();
 
- Done:
-       device_pm_unlock();
-
        return error;
 }