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| author | Luis R. Rodriguez <lrodriguez@atheros.com> | 2010-09-16 15:12:26 -0400 |
|---|---|---|
| committer | John W. Linville <linville@tuxdriver.com> | 2010-09-16 15:46:09 -0400 |
| commit | 8ab2cd09fecc8819bbaee2d0fd8f3a092d866ce3 (patch) | |
| tree | 95c55319794f0c9f09a6aa3abb3d676f281d75c6 /drivers/net/wireless/ath/ath9k/recv.c | |
| parent | 0f529e98498ff1a8bb264958b5fe7c0aa308d5dc (diff) | |
| download | lwn-8ab2cd09fecc8819bbaee2d0fd8f3a092d866ce3.tar.gz lwn-8ab2cd09fecc8819bbaee2d0fd8f3a092d866ce3.zip | |
ath9k: fix power save race conditions
ath9k has a race on putting the chip into network sleep and
having registers read from hardware. The race occurs because
although ath9k_ps_restore() locks its own callers it makes use
of some variables which get altered in the driver at different
code paths. The variables are the ps_enabled and ps_flags.
This is easily reprodicible in large network environments when
roaming with the wpa_supplicant simple bgscan. You'd get some
0xdeadbeef read out on certain registers such as:
ath: timeout (100000 us) on reg 0x806c: 0xdeadbeef & 0x01f00000 != 0x00000000
ath: RX failed to go idle in 10 ms RXSM=0xdeadbeef
ath: timeout (100000 us) on reg 0x7000: 0xdeadbeef & 0x00000003 != 0x00000000
ath: Chip reset failed
The fix is to protect the ath9k_config(hw, IEEE80211_CONF_CHANGE_PS)
calls with a spin_lock_irqsave() which will disable contendors for
these variables from interrupt context, timers, re-entry from mac80211
on the same callback, and most importantly from ath9k_ps_restore()
which is the only call which will put the device into network sleep.
There are quite a few threads and bug reports on these a few of them are:
https://bugs.launchpad.net/ubuntu/karmic/+source/linux/+bug/407040
http://code.google.com/p/chromium-os/issues/detail?id=5709
http://code.google.com/p/chromium-os/issues/detail?id=5943
Stable fixes apply to [2.6.32+]
Cc: stable@kernel.org
Cc: Paul Stewart <pstew@google.com>
Cc: Amod Bodas <amod.bodas@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Diffstat (limited to 'drivers/net/wireless/ath/ath9k/recv.c')
| -rw-r--r-- | drivers/net/wireless/ath/ath9k/recv.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c index f921aa20b301..3e7b8fe36044 100644 --- a/drivers/net/wireless/ath/ath9k/recv.c +++ b/drivers/net/wireless/ath/ath9k/recv.c @@ -1640,6 +1640,7 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp) u8 rx_status_len = ah->caps.rx_status_len; u64 tsf = 0; u32 tsf_lower = 0; + unsigned long flags; if (edma) dma_type = DMA_BIDIRECTIONAL; @@ -1748,11 +1749,13 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp) sc->rx.rxotherant = 0; } + spin_lock_irqsave(&sc->sc_pm_lock, flags); if (unlikely(ath9k_check_auto_sleep(sc) || (sc->ps_flags & (PS_WAIT_FOR_BEACON | PS_WAIT_FOR_CAB | PS_WAIT_FOR_PSPOLL_DATA)))) ath_rx_ps(sc, skb); + spin_unlock_irqrestore(&sc->sc_pm_lock, flags); if (ah->caps.hw_caps & ATH9K_HW_CAP_ANT_DIV_COMB) ath_ant_comb_scan(sc, &rs); |