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    SubjectRe: b43 locks the machine when resuming after suspend to disk
    Date
    On Wednesday, 2 of July 2008, Giacomo Mulas wrote:
    > I tried searching on the list for this, before posting, but searching the
    > mailing list archives with keywords such as b43, suspend, resume... brings
    > up such a ludicrous amount of threads that it's not realistic to check them
    > all, so just tell me what to look for if it's been asked already.
    >
    > Whenever I do a suspend to disk after using b43, the computer freezes hard
    > as soon as it attempts again to access b43 after resume.
    >
    > Minimal how to reproduce the freeze:
    > 1) modprobe b43
    > 2) hibernate (using any suspend to disk, which one is irrelevant)
    > 3) resume
    > 4) ifconfig wlan0 up
    >
    > This has been happening (at least) since b43 was included in the mainline
    > kernel, on my Asus A6K laptop running an x86_64 kernel (now the latest
    > 2.6.25 stable release or compiled from the latest released debian sid
    > sources). The nvidia module is not responsible: I explicitely booted my
    > laptop in single user mode without any unnecessary modules, same result. It
    > does not happen using the windows driver with ndiswrapper (which I would
    > prefer to avoid for other reasons), so it definitely depends on b43 or
    > something it depends on. Unloading and reloading the b43 module and all the
    > other modules it depends on does not change anything. Just loading the
    > module once, hibernating and resuming means freeze-up as soon as the module
    > is actually initialised next time, regardless of it having been unloaded and
    > reloaded any number of times before or after the suspend-resume cycle. No
    > oopses, nothing on system logs, just instant freeze-up. Is there some
    > testing a user can do to help nailing this? I am not a kernel developer,
    > even if I am a decent C programmer.
    >
    > Please CC me on replies, I am not on the list.

    I think you need the appended patch, but it only applies to linux-next.

    Thanks,
    Rafael

    ---
    When a driver rejects a frame in it's ->tx() callback, it must also
    stop queues, otherwise mac80211 can go into a loop here. Detect this
    situation and abort the loop after five retries, warning about the
    driver bug.

    Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
    ---
    net/mac80211/tx.c | 9 ++++++++-
    1 file changed, 8 insertions(+), 1 deletion(-)

    Index: linux-next/net/mac80211/tx.c
    ===================================================================
    --- linux-next.orig/net/mac80211/tx.c
    +++ linux-next/net/mac80211/tx.c
    @@ -1144,7 +1144,7 @@ static int ieee80211_tx(struct net_devic
    struct ieee80211_tx_data tx;
    ieee80211_tx_result res_prepare;
    struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
    - int ret, i;
    + int ret, i, retries = 0;
    u16 queue;

    queue = skb_get_queue_mapping(skb);
    @@ -1206,6 +1206,13 @@ retry:
    */
    if (!__netif_subqueue_stopped(local->mdev, queue)) {
    clear_bit(queue, local->queues_pending);
    + retries++;
    + /*
    + * Driver bug, it's rejecting packets but
    + * not stopping queues.
    + */
    + if (WARN_ON_ONCE(retries > 5))
    + goto drop;
    goto retry;
    }
    store->skb = skb;

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