From 3ba405db1c1b05d157474c71e559393f7ea436ad Mon Sep 17 00:00:00 2001 From: Claudiu Manoil Date: Mon, 14 Oct 2013 17:05:09 +0300 Subject: [PATCH] gianfar: Simplify MQ polling to avoid soft lockup Under certain low traffic conditions, the single core devices with multiple Rx/Tx queues (MQ mode) may reach soft lockup due to gfar_poll not returning in proper time. The following exception was obtained using iperf on a 100Mbit half-duplex link, for a p1010 single core device: BUG: soft lockup - CPU#0 stuck for 23s! [iperf:2847] Modules linked in: CPU: 0 PID: 2847 Comm: iperf Not tainted 3.12.0-rc3 #16 task: e8bf8000 ti: eeb16000 task.ti: ee646000 NIP: c0255b6c LR: c0367ae8 CTR: c0461c18 REGS: eeb17e70 TRAP: 0901 Not tainted (3.12.0-rc3) MSR: 00029000 CR: 44228428 XER: 20000000 GPR00: c0367ad4 eeb17f20 e8bf8000 ee01f4b4 00000008 ffffffff ffffffff 00000000 GPR08: 000000c0 00000008 000000ff ffffffc0 000193fe NIP [c0255b6c] find_next_bit+0xb8/0xc4 LR [c0367ae8] gfar_poll+0xc8/0x1d8 Call Trace: [eeb17f20] [c0367ad4] gfar_poll+0xb4/0x1d8 (unreliable) [eeb17f70] [c0422100] net_rx_action+0xa4/0x158 [eeb17fa0] [c003ec6c] __do_softirq+0xcc/0x17c [eeb17ff0] [c000c28c] call_do_softirq+0x24/0x3c [ee647cc0] [c0004660] do_softirq+0x6c/0x94 [ee647ce0] [c003eb9c] local_bh_enable+0x9c/0xa0 [ee647cf0] [c0454fe8] tcp_prequeue_process+0xa4/0xdc [ee647d10] [c0457e44] tcp_recvmsg+0x498/0x96c [ee647d80] [c047b630] inet_recvmsg+0x40/0x64 [ee647da0] [c040ca8c] sock_recvmsg+0x90/0xc0 [ee647e30] [c040edb8] SyS_recvfrom+0x98/0xfc To prevent this, the outer while() loop has been removed allowing gfar_poll() to return faster even if there's still budget left. Also, there's no need to recompute the budget per Rx queue anymore. Signed-off-by: Claudiu Manoil Signed-off-by: David S. Miller --- drivers/net/ethernet/freescale/gianfar.c | 87 ++++++++++++++------------------ 1 file changed, 38 insertions(+), 49 deletions(-) diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c index c4eaade..186dc4a 100644 --- a/drivers/net/ethernet/freescale/gianfar.c +++ b/drivers/net/ethernet/freescale/gianfar.c @@ -2900,7 +2900,7 @@ static int gfar_poll(struct napi_struct *napi, int budget) struct gfar_priv_rx_q *rx_queue = NULL; int work_done = 0, work_done_per_q = 0; int i, budget_per_q = 0; - int has_tx_work; + int has_tx_work = 0; unsigned long rstat_rxf; int num_act_queues; @@ -2915,62 +2915,51 @@ static int gfar_poll(struct napi_struct *napi, int budget) if (num_act_queues) budget_per_q = budget/num_act_queues; - while (1) { - has_tx_work = 0; - for_each_set_bit(i, &gfargrp->tx_bit_map, priv->num_tx_queues) { - tx_queue = priv->tx_queue[i]; - /* run Tx cleanup to completion */ - if (tx_queue->tx_skbuff[tx_queue->skb_dirtytx]) { - gfar_clean_tx_ring(tx_queue); - has_tx_work = 1; - } + for_each_set_bit(i, &gfargrp->tx_bit_map, priv->num_tx_queues) { + tx_queue = priv->tx_queue[i]; + /* run Tx cleanup to completion */ + if (tx_queue->tx_skbuff[tx_queue->skb_dirtytx]) { + gfar_clean_tx_ring(tx_queue); + has_tx_work = 1; } + } - for_each_set_bit(i, &gfargrp->rx_bit_map, priv->num_rx_queues) { - /* skip queue if not active */ - if (!(rstat_rxf & (RSTAT_CLEAR_RXF0 >> i))) - continue; - - rx_queue = priv->rx_queue[i]; - work_done_per_q = - gfar_clean_rx_ring(rx_queue, budget_per_q); - work_done += work_done_per_q; - - /* finished processing this queue */ - if (work_done_per_q < budget_per_q) { - /* clear active queue hw indication */ - gfar_write(®s->rstat, - RSTAT_CLEAR_RXF0 >> i); - rstat_rxf &= ~(RSTAT_CLEAR_RXF0 >> i); - num_act_queues--; - - if (!num_act_queues) - break; - /* recompute budget per Rx queue */ - budget_per_q = - (budget - work_done) / num_act_queues; - } - } + for_each_set_bit(i, &gfargrp->rx_bit_map, priv->num_rx_queues) { + /* skip queue if not active */ + if (!(rstat_rxf & (RSTAT_CLEAR_RXF0 >> i))) + continue; - if (work_done >= budget) - break; + rx_queue = priv->rx_queue[i]; + work_done_per_q = + gfar_clean_rx_ring(rx_queue, budget_per_q); + work_done += work_done_per_q; + + /* finished processing this queue */ + if (work_done_per_q < budget_per_q) { + /* clear active queue hw indication */ + gfar_write(®s->rstat, + RSTAT_CLEAR_RXF0 >> i); + num_act_queues--; + + if (!num_act_queues) + break; + } + } - if (!num_act_queues && !has_tx_work) { + if (!num_act_queues && !has_tx_work) { - napi_complete(napi); + napi_complete(napi); - /* Clear the halt bit in RSTAT */ - gfar_write(®s->rstat, gfargrp->rstat); + /* Clear the halt bit in RSTAT */ + gfar_write(®s->rstat, gfargrp->rstat); - gfar_write(®s->imask, IMASK_DEFAULT); + gfar_write(®s->imask, IMASK_DEFAULT); - /* If we are coalescing interrupts, update the timer - * Otherwise, clear it - */ - gfar_configure_coalescing(priv, gfargrp->rx_bit_map, - gfargrp->tx_bit_map); - break; - } + /* If we are coalescing interrupts, update the timer + * Otherwise, clear it + */ + gfar_configure_coalescing(priv, gfargrp->rx_bit_map, + gfargrp->tx_bit_map); } return work_done; -- 2.7.4