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author | Claudiu Manoil <claudiu.manoil@freescale.com> | 2013-10-14 17:05:09 +0300 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2013-10-18 15:54:43 -0400 |
commit | 3ba405db1c1b05d157474c71e559393f7ea436ad (patch) | |
tree | 89895769b4a4a7e78674f7d1b4503b94ce20635b /drivers/net/ethernet/freescale | |
parent | 9877b25382e770618d0a36a3024d8a3c67eee9ea (diff) | |
download | op-kernel-dev-3ba405db1c1b05d157474c71e559393f7ea436ad.zip op-kernel-dev-3ba405db1c1b05d157474c71e559393f7ea436ad.tar.gz |
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 <CE,EE,ME> 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 <claudiu.manoil@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/ethernet/freescale')
-rw-r--r-- | drivers/net/ethernet/freescale/gianfar.c | 87 |
1 files 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; |