Hi, Recently Felix improved bgmac driver to be smarter in situation where new packets were Tx/Rx-ed during bgmac_poll execution. It was handled in: eb64e29 bgmac: leave interrupts disabled as long as there is work to do http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=eb64e2923a886441c7b322f138b36029f3fa6a36 With above change, after handling all skb-s in bgmac_poll, bgmac checks if there are new sbk-s to be handled. If so, it doesn't call napi_complete & it doesn't enable interrupts.
Above commit was merged for 4.1 kernel, but I work with OpenWrt based on older releases, so I have all bgmac changes backported to 3.8.11 and 4.0. With 3.8.11 Felix's change seems to be working fine, I did some debugging: [ 44.970000] [bgmac_interrupt] int_status & int_mask = 0x01000000 [ 44.980000] [bgmac_poll] START weight:64 [ 44.990000] [bgmac_poll] Read handled:0 skb-s [ 44.990000] [bgmac_poll] Read IRQ status again BGMAC_IS_TX0:0 BGMAC_IS_RX:0 [ 45.000000] [bgmac_poll] Read skb-s < weight, calling napi_complete, en IRQs [ 45.010000] [bgmac_poll] END returning handled:0 [ 48.040000] [bgmac_interrupt] int_status & int_mask = 0x01000000 [ 48.050000] [bgmac_poll] START weight:64 [ 48.060000] [bgmac_poll] Read handled:0 skb-s [ 48.060000] [bgmac_poll] Read IRQ status again BGMAC_IS_TX0:0 BGMAC_IS_RX:0 [ 48.070000] [bgmac_poll] Read skb-s < weight, calling napi_complete, en IRQs [ 48.080000] [bgmac_poll] END returning handled:0 [ 48.100000] [bgmac_poll] START weight:64 [ 48.110000] [bgmac_poll] Read handled:1 skb-s [ 48.110000] [bgmac_poll] Read IRQ status again BGMAC_IS_TX0:1 BGMAC_IS_RX:1 [ 48.120000] [bgmac_poll] END more skb-s to handle, returning handled:1 [ 48.130000] [bgmac_poll] START weight:64 [ 48.130000] [bgmac_poll] Read handled:1 skb-s [ 48.140000] [bgmac_poll] Read IRQ status again BGMAC_IS_TX0:0 BGMAC_IS_RX:0 [ 48.150000] [bgmac_poll] Read skb-s < weight, calling napi_complete, en IRQs [ 48.160000] [bgmac_poll] END returning handled:1 Please note that at 48.120000 bgmac decided bgmac_poll should be called again and it didn't call napi_complete & didn't enable IRQs. It simply returned 1. NAPI behaved just like we expected, bgmac_poll was called again a moment later. It handled skb-s that appeared meanwhile and ended calling napi_complete and returning 1. Now, it fails badly for me at all when using kernel 4.0.0: [ 52.800000] [bgmac_interrupt] int_status & int_mask = 0x01000000 [ 52.800000] [bgmac_poll] START weight:64 [ 52.810000] [bgmac_poll] Read handled:0 skb-s [ 52.810000] [bgmac_poll] Read IRQ status again BGMAC_IS_TX0:0 BGMAC_IS_RX:0 [ 52.820000] [bgmac_poll] Read skb-s < weight, calling napi_complete, en IRQs [ 52.830000] [bgmac_poll] END returning handled:0 [ 54.610000] [bgmac_interrupt] int_status & int_mask = 0x01000000 [ 54.620000] [bgmac_poll] START weight:64 [ 54.630000] [bgmac_poll] Read handled:0 skb-s [ 54.630000] [bgmac_poll] Read IRQ status again BGMAC_IS_TX0:0 BGMAC_IS_RX:0 [ 54.640000] [bgmac_poll] Read skb-s < weight, calling napi_complete, en IRQs [ 54.650000] [bgmac_poll] END returning handled:0 [ 55.900000] [bgmac_interrupt] int_status & int_mask = 0x01000000 [ 55.910000] [bgmac_poll] START weight:64 [ 55.920000] [bgmac_poll] Read handled:1 skb-s [ 55.920000] [bgmac_poll] Read IRQ status again BGMAC_IS_TX0:1 BGMAC_IS_RX:1 [ 55.930000] [bgmac_poll] END more skb-s to handle, returning handled:1 As you can see, at 55.930000 bgmac also decided bgmac_poll should be called again. It didn't call napi_complete, didn't enable IRQs. It simply returned 1. Just like with kernel 3.8.11. It this case however, NAPI never called bgmac_poll again. It resulted in bgmac hanging (IRQs are off, bgmac expects bgmac_poll to be called). Can you help us with this, please? Does bgmac use NAPI incorrectly? Were there some important changes in 3.19 or 4.0? -- Rafał
diff --git a/drivers/net/ethernet/broadcom/bgmac.c b/drivers/net/ethernet/broadcom/bgmac.c index 4929932..40ce34d 100644 --- a/drivers/net/ethernet/broadcom/bgmac.c +++ b/drivers/net/ethernet/broadcom/bgmac.c @@ -1219,6 +1219,7 @@ static irqreturn_t bgmac_interrupt(int irq, void *dev_id) struct bgmac *bgmac = netdev_priv(dev_id); u32 int_status = bgmac_read(bgmac, BGMAC_INT_STATUS); + pr_info("[%s] int_status:0x%08x & int_mask:0x%08x = 0x%08x\n", __FUNCTION__, int_status, bgmac->int_mask, int_status & bgmac->int_mask); int_status &= bgmac->int_mask; if (!int_status) @@ -1240,22 +1241,31 @@ static int bgmac_poll(struct napi_struct *napi, int weight) { struct bgmac *bgmac = container_of(napi, struct bgmac, napi); int handled = 0; + u32 int_status; + pr_info("[%s] START weight:%d\n", __FUNCTION__, weight); /* Ack */ bgmac_write(bgmac, BGMAC_INT_STATUS, ~0); bgmac_dma_tx_free(bgmac, &bgmac->tx_ring[0]); handled += bgmac_dma_rx_read(bgmac, &bgmac->rx_ring[0], weight); + pr_info("[%s] Read handled:%d skb-s\n", __FUNCTION__, handled); /* Poll again if more events arrived in the meantime */ - if (bgmac_read(bgmac, BGMAC_INT_STATUS) & (BGMAC_IS_TX0 | BGMAC_IS_RX)) + int_status = bgmac_read(bgmac, BGMAC_INT_STATUS); + pr_info("[%s] Read IRQ status again BGMAC_IS_TX0:%d BGMAC_IS_RX:%d\n", __FUNCTION__, !!(int_status & BGMAC_IS_TX0), !!(int_status & BGMAC_IS_RX)); + if (int_status & (BGMAC_IS_TX0 | BGMAC_IS_RX)) { + pr_info("[%s] END more skb-s to handle, returning handled:%d\n", __FUNCTION__, handled); return handled; + } if (handled < weight) { + pr_info("[%s] Read skb-s < weight, calling napi_complete, en IRQs\n", __FUNCTION__); napi_complete(napi); bgmac_chip_intrs_on(bgmac); } + pr_info("[%s] END returning handled:%d\n", __FUNCTION__, handled); return handled; }