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SubjectRe: [PATCH v3 6/8] remoteproc: Introduce "panic" callback in ops
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Quoting Bjorn Andersson (2020-02-10 16:50:57)
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index 097f33e4f1f3..8b6932027d36 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -2216,10 +2218,53 @@ void rproc_report_crash(struct rproc *rproc, enum rproc_crash_type type)
> }
> EXPORT_SYMBOL(rproc_report_crash);
>
> +static int rproc_panic_handler(struct notifier_block *nb, unsigned long event,
> + void *ptr)
> +{
> + unsigned int longest = 0;
> + struct rproc *rproc;
> + unsigned int d;
> + int locked;
> +
> + locked = mutex_trylock(&rproc_list_mutex);
> + if (!locked) {
> + pr_err("Failed to acquire rproc list lock, won't call panic functions\n");
> + return NOTIFY_DONE;
> + }
> +
> + list_for_each_entry(rproc, &rproc_list, node) {
> + if (!rproc->ops->panic || rproc->state != RPROC_RUNNING)
> + continue;
> +
> + d = rproc->ops->panic(rproc);
> + if (d > longest)
> + longest = d;

Could be

d = max(longest, d);

> + }
> +
> + mutex_unlock(&rproc_list_mutex);
> +
> + /* Delay panic for the longest requested duration */
> + mdelay(longest);

Is this to flush caches? Maybe indicate that in the comment.

> +
> + return NOTIFY_DONE;
> +}
> +
> +static void __init rproc_init_panic(void)
> +{
> + rproc_panic_nb.notifier_call = rproc_panic_handler;
> + atomic_notifier_chain_register(&panic_notifier_list, &rproc_panic_nb);

This is an atomic notifier, but the notifier function takes a mutex,
which sleeps. It should use spinlocks, and never sleep, given that panic
can be called from anywhere.

> +}
> +
> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> index 16ad66683ad0..14f05f26cbcd 100644
> --- a/include/linux/remoteproc.h
> +++ b/include/linux/remoteproc.h
> @@ -369,6 +369,8 @@ enum rsc_handling_status {
> * expects to find it
> * @sanity_check: sanity check the fw image
> * @get_boot_addr: get boot address to entry point specified in firmware
> + * @panic: optional callback to react to system panic, core will delay
> + * panic at least the returned number of milliseconds
> */
> struct rproc_ops {
> int (*start)(struct rproc *rproc);
> @@ -383,6 +385,7 @@ struct rproc_ops {
> int (*load)(struct rproc *rproc, const struct firmware *fw);
> int (*sanity_check)(struct rproc *rproc, const struct firmware *fw);
> u32 (*get_boot_addr)(struct rproc *rproc, const struct firmware *fw);
> + unsigned int (*panic)(struct rproc *rproc);

Maybe should be unsigned long to match other "timeouts" in the kernel.

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