Re: [PATCH 1/1] EDAC: fix edac core deadlock when removing a device

From: Andrew Morton
Date: Thu Dec 18 2008 - 17:44:09 EST


On Thu, 18 Dec 2008 13:09:18 +0800
Harry Ciao <qingtao.cao@xxxxxxxxxxxxx> wrote:

> To remove an edac device, all pending work must be complete. At that point,
> it is safe to remove the edac_dev structure.
>
> If the pending work is not properly cleared and proper care is not taken
> when waiting for it's completion, the following stack trace result:
>
> ...
>
> --- a/drivers/edac/edac_device.c
> +++ b/drivers/edac/edac_device.c
> @@ -394,6 +394,12 @@ static void edac_device_workq_function(struct work_struct *work_req)
>
> mutex_lock(&device_ctls_mutex);
>
> + /* If we are being removed, bail out immediately */
> + if (edac_dev->op_state == OP_OFFLINE) {
> + mutex_unlock(&device_ctls_mutex);
> + return;
> + }
> +
> /* Only poll controllers that are running polled and have a check */
> if ((edac_dev->op_state == OP_RUNNING_POLL) &&
> (edac_dev->edac_check != NULL)) {
> @@ -585,14 +591,14 @@ struct edac_device_ctl_info *edac_device_del_device(struct device *dev)
> /* mark this instance as OFFLINE */
> edac_dev->op_state = OP_OFFLINE;
>
> - /* clear workq processing on this instance */
> - edac_device_workq_teardown(edac_dev);
> -
> /* deregister from global list */
> del_edac_device_from_global_list(edac_dev);
>
> mutex_unlock(&device_ctls_mutex);
>
> + /* clear workq processing on this instance */
> + edac_device_workq_teardown(edac_dev);
> +
> /* Tear down the sysfs entries for this instance */
> edac_device_remove_sysfs(edac_dev);
>

Is the change to edac_device_workq_function() necessary?
edac_device_workq_teardown()'s call to cancel_delayed_work() will
ensure that edac_device_workq_function() isn't running.

Incidentally, edac_device_workq_teardown() is an open-coded
cancel_delayed_work_sync().

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