Re: [PATCH 1/1]: Thaws refrigerated bdi flusher threads before invoking kthread_stop on them

Rafael J. Wysocki
2009-11-11T11:59:04Z

On Wednesday 11 November 2009, Romit Dasgupta wrote:
> Hello Rafael,
> As suggested I have added the relevant information in the
> changelog. The patch is below:
> > For completness, below is the information from the Romit's introductory message
> > (Romit, I really think that should go into the chagelog):
>
> Kicks out frozen bdi flusher task out of the refrigerator when the said task
> needs to exit.
> Steps to reproduce this.
> 1) Mount a file system from MMC/SD card.
> 2) Unmount the file system. This creates a flusher task.
> 3) Attempt suspend to RAM. System is unresponsive.
>
> This is because the bdi flusher thread is already in the refrigerator and will
> remain so until it is thawed. The MMC driver suspend routine ultimately will
> issue a 'kthread_stop' on the bdi flusher thread and will block until the
> flusher thread is exited. Since the bdi flusher thread is in the refrigerator
> it never cleans up until thawed.
>
> Signed-off-by: Romit Dasgupta <romit@ti.com>

Thanks! I'd still like to know that this change is fine with Jens, though.

Rafael

> ---
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index 5a37e20..c757b05 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -606,8 +606,11 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
> * Finally, kill the kernel threads. We don't need to be RCU
> * safe anymore, since the bdi is gone from visibility.
> */
> - list_for_each_entry(wb, &bdi->wb_list, list)
> + list_for_each_entry(wb, &bdi->wb_list, list) {
> + if (unlikely(frozen(wb->task)))
> + wb->task->flags &= ~PF_FROZEN;
> kthread_stop(wb->task);
> + }
> }
>
> void bdi_unregister(struct backing_dev_info *bdi)