On Fri, Apr 27, 2018 at 04:35:00PM +0100, James Morse wrote:

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.

These two are repeated from patch 1.

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..

Next patch removes it so I guess you don't have to talk about it here.

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>
Reviewed-by: Punit Agrawal <redacted>

---
Changes since v1:
 * Tidied up _in_nmi_notify_one().

 drivers/acpi/apei/ghes.c | 100 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 65 insertions(+), 35 deletions(-)

...

+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)

		... && !ret

like the rest of the file.

+		irq_work_queue(&ghes_proc_irq_work);
+
+	return ret;
+}
+
 static unsigned long ghes_esource_prealloc_size(
 	const struct acpi_hest_generic *generic)
 {

-- 
Regards/Gruss,
    Boris.

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