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, 6 insertions, 0 deletions

diff --git a/drivers/firewire/fw-topology.c b/drivers/firewire/fw-topology.c
index 0fc9b000e99d..172c1867e9aa 100644
--- a/drivers/firewire/fw-topology.c
+++ b/drivers/firewire/fw-topology.c
@@ -21,6 +21,7 @@
 #include <linux/module.h>
 #include <linux/wait.h>
 #include <linux/errno.h>
+#include <asm/system.h>
 #include "fw-transaction.h"
 #include "fw-topology.h"
 
@@ -518,6 +519,11 @@ fw_core_handle_bus_reset(struct fw_card *card,
                 card->bm_retries = 0;
 
         card->node_id = node_id;
+        /*
+         * Update node_id before generation to prevent anybody from using
+         * a stale node_id together with a current generation.
+         */
+        smp_wmb();
         card->generation = generation;
         card->reset_jiffies = jiffies;
         schedule_delayed_work(&card->work, 0);