From b5d2a5e04e6a26cb3f77af8cbc31e74c361d706c Mon Sep 17 00:00:00 2001 From: Stefan Richter Date: Fri, 25 Jan 2008 18:57:41 +0100 Subject: firewire: enforce access order between generation and node ID, fix "giving up on config rom" MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed by Nick Piggin . Verified to fix 'giving up on config rom' issues on multiple system and drive combinations that were previously affected. Signed-off-by: Jarod Wilson Signed-off-by: Kristian Høgsberg --- drivers/firewire/fw-device.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'drivers/firewire/fw-device.h') diff --git a/drivers/firewire/fw-device.h b/drivers/firewire/fw-device.h index 894d4a92a18..0854fe2bc11 100644 --- a/drivers/firewire/fw-device.h +++ b/drivers/firewire/fw-device.h @@ -35,6 +35,18 @@ struct fw_attribute_group { struct attribute *attrs[11]; }; +/* + * Note, fw_device.generation always has to be read before fw_device.node_id. + * Use SMP memory barriers to ensure this. Otherwise requests will be sent + * to an outdated node_id if the generation was updated in the meantime due + * to a bus reset. + * + * Likewise, fw-core will take care to update .node_id before .generation so + * that whenever fw_device.generation is current WRT the actual bus generation, + * fw_device.node_id is guaranteed to be current too. + * + * The same applies to fw_device.card->node_id vs. fw_device.generation. + */ struct fw_device { atomic_t state; struct fw_node *node; -- cgit v1.2.3