Re: [RFC 1/2] remoteproc: sysfs: authorize rproc shutdown when rproc is crashed

Mathieu Poirier
2020-03-25T17:57:54Z

Hi Loic,

On Wed, Mar 11, 2020 at 11:54:31AM +0100, Loic Pallardy wrote:
> When remoteproc recovery is disabled and rproc crashed, user space
> client has no way to reboot co-processor except by a complete platform
> reboot.
> Indeed rproc_shutdown() is called by sysfs state_store() only is rproc
> state is RPROC_RUNNING.
>
> This patch offers the possibility to shutdown the co-processor if
> it is in RPROC_CRASHED state and so to restart properly co-processor
> from sysfs interface.

If recovery is disabled on an rproc the platform likely intended to have a hard
reboot and as such we should not be concerned about this case.

Where I think we have a problem, something that is asserted by looking at your 2
patches, is cases where rproc_trigger_recovery() fails. That leaves the system
in a state where it can't be recovered, something the remoteproc core should not
allow.

>
> Signed-off-by: Loic Pallardy <loic.pallardy@st.com>
> ---
> drivers/remoteproc/remoteproc_core.c | 2 +-
> drivers/remoteproc/remoteproc_sysfs.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index 097f33e4f1f3..7ac87a75cd1b 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -1812,7 +1812,7 @@ void rproc_shutdown(struct rproc *rproc)
> if (!atomic_dec_and_test(&rproc->power))
> goto out;
>
> - ret = rproc_stop(rproc, false);
> + ret = rproc_stop(rproc, rproc->state == RPROC_CRASHED);

Please add a comment that explains how we can be in rproc_shutdown() when the
processor has crashed and point to rproc_trigger_recovery(). See below for more
details.

> if (ret) {
> atomic_inc(&rproc->power);
> goto out;
> diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
> index 7f8536b73295..1029458a4678 100644
> --- a/drivers/remoteproc/remoteproc_sysfs.c
> +++ b/drivers/remoteproc/remoteproc_sysfs.c
> @@ -101,7 +101,7 @@ static ssize_t state_store(struct device *dev,
> if (ret)
> dev_err(&rproc->dev, "Boot failed: %d\n", ret);
> } else if (sysfs_streq(buf, "stop")) {
> - if (rproc->state != RPROC_RUNNING)
> + if (rproc->state != RPROC_RUNNING && rproc->state != RPROC_CRASHED)
> return -EINVAL;

Wouldn't it be better to just prevent the MCU to stay in a crashed state (when
recovery is not disabled)?

I like what you did in the next patch where the state of the MCU is set to
RPROC_CRASHED in case of failure, so that we keep. I also think the hunk
above is correct. All that is left is to call rproc_shutdown() directly in
rproc_trigger_recovery() when something goes wrong. I would also add a
dev_err() so that users have a clue of what happened.

That would leave the system in a stable state without having to add intelligence
to state_store().

Let me know that you think...

Mathieu

>
> rproc_shutdown(rproc);
> --
> 2.7.4
>