firewire: enforce access order between generation and node ID, fix "giving up on config rom"

fw_device.node_id and fw_device.generation are accessed without mutexes.
We have to ensure that all readers will get to see node_id updates
before generation updates.

Fixes an inability to recognize devices after "giving up on config rom",
https://bugzilla.redhat.com/show_bug.cgi?id=429950

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

Reviewed by Nick Piggin <nickpiggin@yahoo.com.au>.

Verified to fix 'giving up on config rom' issues on multiple system and
drive combinations that were previously affected.

Signed-off-by: Jarod Wilson <jwilson@redhat.com>
Signed-off-by: Kristian Høgsberg <krh@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/firewire/fw-cdev.c b/drivers/firewire/fw-cdev.c
index cea8a799799f..7e73cbaa4121 100644
--- a/drivers/firewire/fw-cdev.c
+++ b/drivers/firewire/fw-cdev.c
@@ -207,6 +207,7 @@ fill_bus_reset_event(struct fw_cdev_event_bus_reset *event,
         event->closure       = client->bus_reset_closure;
         event->type          = FW_CDEV_EVENT_BUS_RESET;
         event->generation    = client->device->generation;
+        smp_rmb();           /* node_id must not be older than generation */
         event->node_id       = client->device->node_id;
         event->local_node_id = card->local_node->node_id;
         event->bm_node_id    = 0; /* FIXME: We don't track the BM. */