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Subject[ 40/89] ath9k: remove sc->rx.rxbuflock to fix a deadlock
Date
3.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Felix Fietkau <nbd@openwrt.org>

commit 463e3ed3eacc8f47866e5d612bd8ee0bcee5e2f0 upstream.

The commit "ath9k: fix rx flush handling" added a deadlock that happens
because ath_rx_tasklet is called in a section that has already taken the
rx buffer lock.

It seems that the only purpose of the rxbuflock was a band-aid fix to the
reset vs rx tasklet race, which has been properly fixed in the commit
"ath9k: add a better fix for the rx tasklet vs rx flush race".

Now that the fix is in, we can safely remove the lock to avoid such issues.

Reported-by: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/wireless/ath/ath9k/ath9k.h | 1 -
drivers/net/wireless/ath/ath9k/recv.c | 13 -------------
2 files changed, 14 deletions(-)

--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -315,7 +315,6 @@ struct ath_rx {
u32 *rxlink;
u32 num_pkts;
unsigned int rxfilter;
- spinlock_t rxbuflock;
struct list_head rxbuf;
struct ath_descdma rxdma;
struct ath_buf *rx_bufptr;
--- a/drivers/net/wireless/ath/ath9k/recv.c
+++ b/drivers/net/wireless/ath/ath9k/recv.c
@@ -254,8 +254,6 @@ rx_init_fail:

static void ath_edma_start_recv(struct ath_softc *sc)
{
- spin_lock_bh(&sc->rx.rxbuflock);
-
ath9k_hw_rxena(sc->sc_ah);

ath_rx_addbuffer_edma(sc, ATH9K_RX_QUEUE_HP,
@@ -267,8 +265,6 @@ static void ath_edma_start_recv(struct a
ath_opmode_init(sc);

ath9k_hw_startpcureceive(sc->sc_ah, !!(sc->hw->conf.flags & IEEE80211_CONF_OFFCHANNEL));
-
- spin_unlock_bh(&sc->rx.rxbuflock);
}

static void ath_edma_stop_recv(struct ath_softc *sc)
@@ -285,7 +281,6 @@ int ath_rx_init(struct ath_softc *sc, in
int error = 0;

spin_lock_init(&sc->sc_pcu_lock);
- spin_lock_init(&sc->rx.rxbuflock);

common->rx_bufsize = IEEE80211_MAX_MPDU_LEN / 2 +
sc->sc_ah->caps.rx_status_len;
@@ -446,7 +441,6 @@ int ath_startrecv(struct ath_softc *sc)
return 0;
}

- spin_lock_bh(&sc->rx.rxbuflock);
if (list_empty(&sc->rx.rxbuf))
goto start_recv;

@@ -467,8 +461,6 @@ start_recv:
ath_opmode_init(sc);
ath9k_hw_startpcureceive(ah, !!(sc->hw->conf.flags & IEEE80211_CONF_OFFCHANNEL));

- spin_unlock_bh(&sc->rx.rxbuflock);
-
return 0;
}

@@ -484,7 +476,6 @@ bool ath_stoprecv(struct ath_softc *sc)
struct ath_hw *ah = sc->sc_ah;
bool stopped, reset = false;

- spin_lock_bh(&sc->rx.rxbuflock);
ath9k_hw_abortpcurecv(ah);
ath9k_hw_setrxfilter(ah, 0);
stopped = ath9k_hw_stopdmarecv(ah, &reset);
@@ -495,7 +486,6 @@ bool ath_stoprecv(struct ath_softc *sc)
ath_edma_stop_recv(sc);
else
sc->rx.rxlink = NULL;
- spin_unlock_bh(&sc->rx.rxbuflock);

if (!(ah->ah_flags & AH_UNPLUGGED) &&
unlikely(!stopped)) {
@@ -1059,7 +1049,6 @@ int ath_rx_tasklet(struct ath_softc *sc,
dma_type = DMA_FROM_DEVICE;

qtype = hp ? ATH9K_RX_QUEUE_HP : ATH9K_RX_QUEUE_LP;
- spin_lock_bh(&sc->rx.rxbuflock);

tsf = ath9k_hw_gettsf64(ah);
tsf_lower = tsf & 0xffffffff;
@@ -1251,8 +1240,6 @@ requeue:
}
} while (1);

- spin_unlock_bh(&sc->rx.rxbuflock);
-
if (!(ah->imask & ATH9K_INT_RXEOL)) {
ah->imask |= (ATH9K_INT_RXEOL | ATH9K_INT_RXORN);
ath9k_hw_set_interrupts(ah);



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