Re: [Drbd-dev] [PATCH] drbd: fix regression 'out of mem, failed to invoke fence-peer helper'

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Oct 01, 2014 at 11:32:29AM +0200, Philipp Reisner wrote:
> From: Lars Ellenberg <lars.ellenberg@linbit.com>
> 
> Stable info:
>   This patch landed in upstream with v3.16 as commit
>   bbc1c5e8ad6dfebf9d13b8a4ccdf66c92913eac9
>   it should go into v3.14+
> 
> Since linux kernel 3.13, kthread_run() internally uses
> wait_for_completion_killable().  We sometimes may use kthread_run()
> while we still have a signal pending, which we used to kick our threads
> out of potentially blocking network functions, causing kthread_run() to
> mistake that as a new fatal signal and fail.
> 
> Fix: flush_signals() before kthread_run().
> 
> Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
> Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
> Signed-off-by: Jens Axboe <axboe@fb.com>
> ---
>  drivers/block/drbd/drbd_nl.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
> index 1b35c45..3f2e167 100644
> --- a/drivers/block/drbd/drbd_nl.c
> +++ b/drivers/block/drbd/drbd_nl.c
> @@ -544,6 +544,12 @@ void conn_try_outdate_peer_async(struct drbd_connection *connection)
>         struct task_struct *opa;
> 
>         kref_get(&connection->kref);
> +       /* We may just have force_sig()'ed this thread
> +        * to get it out of some blocking network function.
> +        * Clear signals; otherwise kthread_run(), which internally uses
> +        * wait_on_completion_killable(), will mistake our pending signal
> +        * for a new fatal signal and fail. */
> +       flush_signals(current);
>         opa = kthread_run(_try_outdate_peer_async, connection, "drbd_async_h");
>         if (IS_ERR(opa)) {
>                 drbd_err(connection, "out of mem, failed to invoke fence-peer helper\n");

This doesn't apply to 3.16-stable or 3.14-stable, can you please provide
a working backport?

thanks,


greg k-h