tx_pending may be set by the user (via ethtool -G) to a low enough value that TG3_TX_WAKEUP_THRESH becomes smaller than MAX_SKB_FRAGS + 1. This may cause the tx queue to be waked when there are in fact not enough descriptors to handle an skb with max frags. This in turn causes tg3_start_xmit() to return NETDEV_TX_BUSY and print error messages. Fix the problem by putting a limit to how low TG3_TX_WAKEUP_THRESH can go.
Signed-off-by: Benjamin Poirier <bpoir...@suse.de> --- I noticed the problem in a 3.0 kernel when setting `ethtool eth0 -G tx 50` and running a netperf TCP_STREAM test. The console fills up with [10597.596155] tg3 0000:06:00.0: eth0: BUG! Tx Ring full when queue awake! The problem in tg3 remains in current kernels though it does not reproduce as easily since "5640f76 net: use a per task frag allocator (v3.7-rc1)". I reproduced on current kernels by using the fail_page_alloc fault injection mechanism to force the creation of skbs with many order-0 frags. Note that the following script may also trigger another bug (NETDEV WATCHDOG), which is fixed in the next patch. $ cat /tmp/doit.sh F="/sys/kernel/debug/fail_page_alloc" echo -1 > "$F/times" echo 0 > "$F/verbose" echo 0 > "$F/ignore-gfp-wait" echo 1 > "$F/task-filter" echo 100 > "$F/probability" netperf -H 192.168.9.30 -l100 -t omni -- -d send & n=$! sleep 0.3 echo 1 > "/proc/$n/make-it-fail" sleep 10 kill "$n" --- drivers/net/ethernet/broadcom/tg3.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c index 3ac5d23..b11c0fd 100644 --- a/drivers/net/ethernet/broadcom/tg3.c +++ b/drivers/net/ethernet/broadcom/tg3.c @@ -202,7 +202,8 @@ static inline void _tg3_flag_clear(enum TG3_FLAGS flag, unsigned long *bits) #endif /* minimum number of free TX descriptors required to wake up TX process */ -#define TG3_TX_WAKEUP_THRESH(tnapi) ((tnapi)->tx_pending / 4) +#define TG3_TX_WAKEUP_THRESH(tnapi) max_t(u32, (tnapi)->tx_pending / 4, \ + MAX_SKB_FRAGS + 1) #define TG3_TX_BD_DMA_MAX_2K 2048 #define TG3_TX_BD_DMA_MAX_4K 4096 -- 1.8.4.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
