From 78a7685e1e44c6d4b6f79c73687b9322e40b040e Mon Sep 17 00:00:00 2001 From: "Luis R. Rodriguez" <lrodriguez@atheros.com> Date: Wed, 20 Oct 2010 16:07:08 -0700 Subject: [PATCH] ath9k: add a debug warning when we cannot stop RX 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> --- drivers/net/wireless/ath/ath9k/recv.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c index c04a940550b..87fabf84e6f 100644 --- a/drivers/net/wireless/ath/ath9k/recv.c +++ b/drivers/net/wireless/ath/ath9k/recv.c @@ -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; } -- 2.20.1