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PM: Do not hold dpm_list_mtx while disabling/enabling nonboot CPUs

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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>
This commit is contained in:
Rafael J. Wysocki
2009-05-24 21:15:07 +02:00
parent 59a3759d0f
commit 32bdfac546
4 changed files with 8 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
kernel/power/main.c
View File

@@ -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;
}