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ath9k: add a debug warning when we cannot stop RX

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We have seen several DMA races when we race against
stopping and starting the PCU. I suspect that when
we cannot stop the PCU we may hit some of these same
races so warn against them for now but only when
debugging (CONFIG_ATH_DEBUG) is enabled.

If you run into this warning and are a developer,
please fix the cause of the warning. The potential
here, although I cannot prove yet, is that the DMA
engine can be confused and start writing to a buffer
that was already DMA'd before and at least the kernel
assumes is not being accessed by hardware anymore.

Cc: Ben Greear <greearb@candelatech.com>
Cc: Kyungwan Nam <kyungwan.nam@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Luis R. Rodriguez 2010-10-20 16:07:08 -07:00 committed by John W. Linville
parent b87b012889
commit 78a7685e1e
1 changed files with 2 additions and 0 deletions
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2
drivers/net/wireless/ath/ath9k/recv.c
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@ -528,6 +528,8 @@ bool ath_stoprecv(struct ath_softc *sc)
sc->rx.rxlink = NULL;
spin_unlock_bh(&sc->rx.rxbuflock);
ATH_DBG_WARN(!stopped, "Could not stop RX, we could be "
"confusing the DMA engine when we start RX up\n");
return stopped;
}