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| author | Andreas Fenkart <andreas.fenkart@streamunlimited.com> | 2013-04-05 07:03:52 +0400 |
|---|---|---|
| committer | John W. Linville <linville@tuxdriver.com> | 2013-04-08 23:28:39 +0400 |
| commit | 333f6b22c5b88a9d856703b440257f46efa714c8 (patch) | |
| tree | 4cc881717c225356f42d0870997332b424e0a2ae /drivers/net/wireless/mwifiex/wmm.c | |
| parent | 6d2344ec6043a2de8cfa9d8f27909a99ca967a08 (diff) | |
| download | linux-333f6b22c5b88a9d856703b440257f46efa714c8.tar.xz | |
mwifiex: fix infinite loop by removing NO_PKT_PRIO_TID
Using NO_PKT_PRIO_TID and tx_pkts_queued to check for an empty
state, can lead to a contradictory state, resulting in an
infinite loop. Currently queueing and dequeuing of packets is
not synchronized, and can happen concurrently. While tx_pkts_queued
is incremented when adding a packet, max prio is set to NO_PKT when
the WMM list is empty. If a packet is added right after the check
for empty, but before setting max prio to NO_PKT, that packet is
trapped and creates an infinite loop.
Because of the new packet, tx_pkts_queued is at least 1, indicating
wmm lists are not empty. Opposing that max prio is NO_PKT, which
means "skip this wmm queue, it has no packets". The infinite loop
results, because the main loop checks the wmm lists for not empty
via tx_pkts_queued, but for dequeing it uses max_prio to see if it
can skip current list. This will never end, unless a new packet is
added which will restore max prio to the level of the trapped packet.
The solution here is to rely on tx_pkts_queued solely for checking
wmm queue to be empty, and drop the NO_PKT define. It does not
address the locking issue.
Signed-off-by: Andreas Fenkart <andreas.fenkart@streamunlimited.com>
Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Diffstat (limited to 'drivers/net/wireless/mwifiex/wmm.c')
| -rw-r--r-- | drivers/net/wireless/mwifiex/wmm.c | 13 |
1 files changed, 6 insertions, 7 deletions
diff --git a/drivers/net/wireless/mwifiex/wmm.c b/drivers/net/wireless/mwifiex/wmm.c index c1d848882fe2..75c8e80bb62f 100644 --- a/drivers/net/wireless/mwifiex/wmm.c +++ b/drivers/net/wireless/mwifiex/wmm.c @@ -916,8 +916,12 @@ mwifiex_wmm_get_highest_priolist_ptr(struct mwifiex_adapter *adapter, do { priv_tmp = bssprio_node->priv; - hqp = &priv_tmp->wmm.highest_queued_prio; + if (atomic_read(&priv_tmp->wmm.tx_pkts_queued) == 0) + goto skip_bss; + + /* iterate over the WMM queues of the BSS */ + hqp = &priv_tmp->wmm.highest_queued_prio; for (i = atomic_read(hqp); i >= LOW_PRIO_TID; --i) { tid_ptr = &(priv_tmp)->wmm. @@ -976,12 +980,7 @@ mwifiex_wmm_get_highest_priolist_ptr(struct mwifiex_adapter *adapter, } while (ptr != head); } - /* No packet at any TID for this priv. Mark as such - * to skip checking TIDs for this priv (until pkt is - * added). - */ - atomic_set(hqp, NO_PKT_PRIO_TID); - +skip_bss: /* Get next bss priority node */ bssprio_node = list_first_entry(&bssprio_node->list, struct mwifiex_bss_prio_node, |