Commits
Claudiu Manoil committed 3ba405db1c1
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>