Date: Mon, 27 Sep 2004 20:27:22 +0200 From: Pierre Beyssac <beyssac@enst.fr> To: freebsd-net@freebsd.org Cc: mlaier@freebsd.org Subject: reproductible hang with if_em Message-ID: <20040927182722.GA1664@bofh.enst.fr>
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Hello, I'm having a problem (under 5.3-BETA, but I don't think it matters much) with the if_em driver on bursty outbound traffic: the card is stuck in a state where it only returns ENOBUFS. No buffers ever become available again, but ifconfig down+up fixes the problem. >From a quick analysis it looks like the TX descriptor cleanup routine em_clean_transmit_interrupts() as called by em_encap() in such cases doesn't manage to find anything free with E1000_TXD_STAT_DD set. The card seems stuck in this state. A simple albeit dirty fix would be to cancel some or all untransmitted packets in such cases. Perhaps this is related to my using the card on a 100Mbps switch. I have a small program to exercise the hang in case someone would like to have a look at it. See below for the result of "sysctl hw.em0.debug_info=1" (notice the not avail1 = 12 and not avail2 = 0 hinting at em_clean_transmit_interrupts). em0: [MPSAFE] em0: bpf attached em0: Ethernet address: 00:0d:56:d0:5c:15 em0: Speed:N/A Duplex:N/A em0: Link is up 100 Mbps Full Duplex em0: Adapter hardware address = 0xc3570b34 em0:tx_int_delay = 66, tx_abs_int_delay = 66 em0:rx_int_delay = 0, rx_abs_int_delay = 66 em0: fifo workaround = 0, fifo_reset = 0 em0: hw tdh = 238, hw tdt = 238 em0: Num Tx descriptors avail = 256 em0: Tx Descriptors not avail1 = 12 em0: Tx Descriptors not avail2 = 0 em0: Std mbuf failed = 0 em0: Std mbuf cluster failed = 0 em0: Driver dropped packets = 0 -- Pierre Beyssac pb@enst.fr
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