On Sat, Feb 23, 2008 at 12:53:11AM +0100, Rafael J. Wysocki wrote:
> Hi Greg,
>
> The appended patch fixes the issue with the new code for suspending/resuming
> devices, related to the fact that some device drivers and CPU hotplug notifiers
> unregister device objects while suspend is in progress, which leads to
> deadlocks.
>
> Please consider taking it for 2.6.25.
>
> Thanks,
> Rafael
>
> ---
> From: Rafael J. Wysocki <rjw@xxxxxxx>
>
> Introduce a mechanism preventing drivers and CPU hotplug notifiers
> from deadlocking suspend/hibernation by unregistering device objects
> while it is in progress. Specifically, make device_del() detect if
> it has been called by the suspending task and automatically defer the
> removal of the device object if that's the case.
>
> Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
> Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> ---
> drivers/base/core.c | 5 +++++
> drivers/base/power/main.c | 9 +++++++++
> drivers/base/power/power.h | 5 +++++
> 3 files changed, 19 insertions(+)
>
> Index: linux-2.6/drivers/base/power/main.c
> ===================================================================
> --- linux-2.6.orig/drivers/base/power/main.c
> +++ linux-2.6/drivers/base/power/main.c
> @@ -59,6 +59,13 @@ static DECLARE_RWSEM(pm_sleep_rwsem);
>
> int (*platform_enable_wakeup)(struct device *dev, int is_on);
>
> +static struct task_struct *suspending_task;
> +
> +bool in_suspend_context(void)
> +{
> + return (suspending_task == current);
> +}
> +
> /**
> * device_pm_add - add a device to the list of active devices
> * @dev: Device to be added to the list
> @@ -272,6 +279,7 @@ static void dpm_resume(void)
> mutex_lock(&dpm_list_mtx);
> }
> mutex_unlock(&dpm_list_mtx);
> + suspending_task = NULL;
> }
>
> /**
> @@ -460,6 +468,7 @@ static int dpm_suspend(pm_message_t stat
> {
> int error = 0;
>
> + suspending_task = current;
> mutex_lock(&dpm_list_mtx);
> while (!list_empty(&dpm_locked)) {
> struct list_head *entry = dpm_locked.prev;
> Index: linux-2.6/drivers/base/core.c
> ===================================================================
> --- linux-2.6.orig/drivers/base/core.c
> +++ linux-2.6/drivers/base/core.c
> @@ -929,6 +929,11 @@ void device_del(struct device *dev)
> struct device *parent = dev->parent;
> struct class_interface *class_intf;
>
> + if (in_suspend_context()) {
> + get_device(dev);
> + device_pm_schedule_removal(dev);
> + return;
> + }
Why are you grabbing an additional reference to the device here? That
would seem to get out of balance when the device is later scheduled for
removal, right?
thanks,
greg k-h
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