[PATCH 02/11] ACPI / APEI: Generalise the estatus queue's add/remove and notify code

Punit Agrawal
2018-02-20T18:26:44Z

A few of typos and comments below.

James Morse <james.morse@arm.com> writes:

> To support asynchronous NMI-like notifications on arm64 we need to use
> the estatus-queue. These patches refactor it to allow multiple APEI
> notification types to use it.
>
> Refactor the estatus queue's pool grow/shrink code and notification
> routine from NOTIFY_NMI's handlers. This will allow another notification
> method to use the estatus queue without duplicating this code.
>
> This patch adds rcu_read_lock()/rcu_read_unlock() around the list
> list_for_each_entry_rcu() walker. These aren't strictly necessary as
> the whole nmi_enter/nmi_exit() window is a spooky RCU read-side
> critical section.
>
> Keep the oops_begin() call for x86, arm64 doesn't have one of these,
> and APEI is the only thing outside arch code calling this..
>
> The existing ghes_estatus_pool_shrink() is folded into the new
> ghes_estatus_queue_shrink_pool() as only the queue uses it.
>
> _in_nmi_notify_one() is separate from the rcu-list walker for a later
> caller that doesn't need to walk a list.
>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> drivers/acpi/apei/ghes.c | 103 +++++++++++++++++++++++++++++++----------------
> 1 file changed, 68 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index e42b587c509b..d3cc5bd5b496 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -749,6 +749,54 @@ static void __process_error(struct ghes *ghes)
> #endif
> }
>
> +static int _in_nmi_notify_one(struct ghes *ghes)
> +{
> + int sev;
> + int ret = -ENOENT;

If ret is initialised to 0 ...

> +
> + if (ghes_read_estatus(ghes, 1)) {
> + ghes_clear_estatus(ghes);
> + return ret;

and return -ENOENT here...

> + } else {
> + ret = 0;
> + }

... then the else block can be dropped.

> +
> + sev = ghes_severity(ghes->estatus->error_severity);
> + if (sev >= GHES_SEV_PANIC) {
> +#ifdef CONFIG_X86
> + oops_begin();
> +#endif

Can you use IS_ENABLED() here as well?

> + ghes_print_queued_estatus();
> + __ghes_panic(ghes);
> + }
> +
> + if (!(ghes->flags & GHES_TO_CLEAR))
> + return ret;
> +
> + __process_error(ghes);
> + ghes_clear_estatus(ghes);
> +
> + return ret;
> +}
> +
> +static int ghes_estatus_queue_notified(struct list_head *rcu_list)
> +{
> + int ret = -ENOENT;
> + struct ghes *ghes;
> +
> + rcu_read_lock();
> + list_for_each_entry_rcu(ghes, rcu_list, list) {
> + if (!_in_nmi_notify_one(ghes))
> + ret = 0;
> + }
> + rcu_read_unlock();
> +
> + if (IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) && ret == 0)
> + irq_work_queue(&ghes_proc_irq_work);
> +
> + return ret;
> +}
> +
> static unsigned long ghes_esource_prealloc_size(
> const struct acpi_hest_generic *generic)
> {
> @@ -764,11 +812,24 @@ static unsigned long ghes_esource_prealloc_size(
> return prealloc_size;
> }
>
> -static void ghes_estatus_pool_shrink(unsigned long len)
> +/* After removing a queue user, we can shrink to pool */
^
the

Thanks,
Punit

> +static void ghes_estatus_queue_shrink_pool(struct ghes *ghes)
> {
> + unsigned long len;
> +
> + len = ghes_esource_prealloc_size(ghes->generic);
> ghes_estatus_pool_size_request -= PAGE_ALIGN(len);
> }
> …