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    SubjectRe: [PATCH] firewire: fw-core: enforce write order when updating fw_device.generation
    Date
    On Thursday 01 November 2007 12:49, Stefan Richter wrote:
    > 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.
    >

    Hi, a few points:

    - can change it to use spinlocks instead? This would be most
    preferable.

    - if not, you need comments.

    - you also seem to be missing rmb()s now. I see a couple in the
    firewire directory, but nothing that seems to be ordering loads
    of these particular fields.

    - use smp_*mb() if you are just ordering regular cacheable RAM
    accesses.

    Also, diffstat is a bit wrong... maybe you posted the wrong version?

    > Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
    > ---
    > drivers/firewire/fw-device.c | 6 ++++++
    > drivers/firewire/fw-topology.c | 1 +
    > 2 files changed, 7 insertions(+)
    >
    > Index: linux/drivers/firewire/fw-device.c
    > ===================================================================
    > --- linux.orig/drivers/firewire/fw-device.c
    > +++ linux/drivers/firewire/fw-device.c
    > @@ -808,6 +813,7 @@ void fw_node_event(struct fw_card *card,
    >
    > device = node->data;
    > device->node_id = node->node_id;
    > + wmb();
    > device->generation = card->generation;
    > if (atomic_read(&device->state) == FW_DEVICE_RUNNING) {
    > PREPARE_DELAYED_WORK(&device->work, fw_device_update);
    > Index: linux/drivers/firewire/fw-topology.c
    > ===================================================================
    > --- linux.orig/drivers/firewire/fw-topology.c
    > +++ linux/drivers/firewire/fw-topology.c
    > @@ -518,6 +518,7 @@ fw_core_handle_bus_reset(struct fw_card
    > card->bm_retries = 0;
    >
    > card->node_id = node_id;
    > + wmb();
    > card->generation = generation;
    > card->reset_jiffies = jiffies;
    > schedule_delayed_work(&card->work, 0);
    -
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