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authorStefan Richter <stefanr@s5r6.in-berlin.de>2008-01-25 12:57:41 -0500
committerStefan Richter <stefanr@s5r6.in-berlin.de>2008-01-30 16:22:27 -0500
commitb5d2a5e04e6a26cb3f77af8cbc31e74c361d706c (patch)
treecfc3b2dc141f643bcf6ef065cca802340b335799 /drivers/firewire/fw-device.h
parentcf5a56ac8083dd04ffe8b9b2ec7895e9bcff44bc (diff)
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>
Diffstat (limited to 'drivers/firewire/fw-device.h')
-rw-r--r--drivers/firewire/fw-device.h12
1 files changed, 12 insertions, 0 deletions
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 {
35 struct attribute *attrs[11]; 35 struct attribute *attrs[11];
36}; 36};
37 37
38/*
39 * Note, fw_device.generation always has to be read before fw_device.node_id.
40 * Use SMP memory barriers to ensure this. Otherwise requests will be sent
41 * to an outdated node_id if the generation was updated in the meantime due
42 * to a bus reset.
43 *
44 * Likewise, fw-core will take care to update .node_id before .generation so
45 * that whenever fw_device.generation is current WRT the actual bus generation,
46 * fw_device.node_id is guaranteed to be current too.
47 *
48 * The same applies to fw_device.card->node_id vs. fw_device.generation.
49 */
38struct fw_device { 50struct fw_device {
39 atomic_t state; 51 atomic_t state;
40 struct fw_node *node; 52 struct fw_node *node;