[RFC] [patch 2/2] powerpc 2.6.21-rt1: fix kernel hang and/or panic
Benjamin Herrenschmidt
benh at kernel.crashing.org
Tue May 15 20:09:02 EST 2007
On Tue, 2007-05-15 at 17:47 +0900, Tsutomu OWA wrote:
> > It occurs on 2.6.21 + patch-2.6.21-rt1 + series of patches that I posted
> > yesterday.
>
> I encountered the following error when doing netperf from other machine
> to Celleb running RT kernel. PREEPT_NONE kernel works just fine as well.
Hrm... sounds a bit weird. I wonder if there's a locking bug in the
driver in the first place.
Linas, what's your take ?
Ben.
> Unable to handle kernel paging request for data at address 0x00000009
> Faulting instruction address: 0xc000000000295434
> Oops: Kernel access of bad area, sig: 11 [#1]
> PREEMPT SMP NR_CPUS=2 NUMA
> Modules linked in:
> NIP: C000000000295434 LR: C000000000295420 CTR: 0000000000000000
> REGS: c0000000095d6e30 TRAP: 0300 Not tainted (2.6.21-rc5-rt7)
> MSR: 8000000000009032 <EE,ME,IR,DR> CR: 24000482 XER: 20000000
> DAR: 0000000000000009, DSISR: 0000000040000000
> TASK = c000000001e7c440[626] 'netserver' THREAD: c0000000095d4000 CPU: 0
> GPR00: 0000000000000800 C0000000095D70B0 C0000000005D77B8 0000000000000001
> GPR04: 0000000000000001 0000000000000000 C0000000095D7080 0000000000000000
> GPR08: C0000000095D7030 0000000000000000 C0000000095D7040 0000000000000000
> GPR12: FC69925300080D5D C0000000004DE680 0000000000000000 0000000000422208
> GPR16: 0000000000400000 0000000000420D10 0000000000000000 C0000000095D7C88
> GPR20: C000000001E7C440 0000000000000000 0000000000000001 C000000008ACEAE0
> GPR24: 0000000000000020 C000000000E50C80 0000000081F84C5E C000000001C00BE0
> GPR28: C000000001C05430 C000000001C00B80 C000000000570F30 C000000001FD1720
> NIP [C000000000295434] .spider_net_xmit+0x1dc/0x448
> LR [C000000000295420] .spider_net_xmit+0x1c8/0x448
> Call Trace:
> [C0000000095D70B0] [C000000000295420] .spider_net_xmit+0x1c8/0x448 (unreliable)
> [C0000000095D7160] [C000000000327EE8] .dev_hard_start_xmit+0x238/0x300
> [C0000000095D7200] [C00000000033A7F4] .__qdisc_run+0xdc/0x2a4
> [C0000000095D72B0] [C00000000032A948] .dev_queue_xmit+0x1b0/0x2fc
> [C0000000095D7350] [C00000000034B470] .ip_output+0x280/0x2d8
> [C0000000095D73F0] [C00000000034C6CC] .ip_queue_xmit+0x448/0x4d8
> [C0000000095D74F0] [C00000000035F6D8] .tcp_transmit_skb+0x850/0x8c0
> [C0000000095D75C0] [C00000000035C394] .__tcp_ack_snd_check+0x84/0xc0
> [C0000000095D7650] [C00000000035E114] .tcp_rcv_established+0x4f0/0x8ac
> [C0000000095D7700] [C000000000365B24] .tcp_v4_do_rcv+0x5c/0x448
> [C0000000095D77D0] [C00000000031C2C4] .release_sock+0x94/0x11c
> [C0000000095D7870] [C000000000354E7C] .tcp_recvmsg+0x374/0x8d8
> [C0000000095D7960] [C00000000031B8A0] .sock_common_recvmsg+0x5c/0x84
> [C0000000095D79F0] [C00000000031921C] .sock_recvmsg+0x110/0x15c
> [C0000000095D7C00] [C00000000031AA50] .sys_recvfrom+0xf0/0x174
> [C0000000095D7D90] [C000000000339368] .compat_sys_socketcall+0x178/0x214
> [C0000000095D7E30] [C000000000008634] syscall_exit+0x0/0x40
> Instruction dump:
> 60000000 81790088 901f000c 913f0018 913f0008 917f0004 48132e8d 60000000
> a019009e 2f800800 409e0038 e9390038 <88690009> 2f830006 419e0010 2f830011
>
> I suspect spidernet expects spin_lock_irqsave()/restore() to disable/enable
> interrupts in vain on RT kernel.
>
> This patch works fine as far as I've tested, but I feel it's a kind of
> workaround. Any comments, suggestions, patches are welcome.
>
> Thanks in advance
>
> Signed-off-by: Tsutomu OWA <tsutomu.owa at toshiba.co.jp>
> -- owa
>
> diff -rup linux-2.6.21-rt1/drivers/net/spider_net.c rt/drivers/net/spider_net.c
> --- linux-2.6.21-rt1/drivers/net/spider_net.c 2007-04-26 12:08:32.000000000 +0900
> +++ rt/drivers/net/spider_net.c 2007-05-07 14:11:24.000000000 +0900
> @@ -688,7 +688,6 @@ spider_net_prepare_tx_descr(struct spide
> struct spider_net_descr *descr;
> struct spider_net_hw_descr *hwdescr;
> dma_addr_t buf;
> - unsigned long flags;
>
> buf = pci_map_single(card->pdev, skb->data, skb->len, PCI_DMA_TODEVICE);
> if (pci_dma_mapping_error(buf)) {
> @@ -699,10 +698,8 @@ spider_net_prepare_tx_descr(struct spide
> return -ENOMEM;
> }
>
> - spin_lock_irqsave(&chain->lock, flags);
> descr = card->tx_chain.head;
> if (descr->next == chain->tail->prev) {
> - spin_unlock_irqrestore(&chain->lock, flags);
> pci_unmap_single(card->pdev, buf, skb->len, PCI_DMA_TODEVICE);
> return -ENOMEM;
> }
> @@ -717,7 +714,6 @@ spider_net_prepare_tx_descr(struct spide
>
> hwdescr->dmac_cmd_status =
> SPIDER_NET_DESCR_CARDOWNED | SPIDER_NET_DMAC_NOCS;
> - spin_unlock_irqrestore(&chain->lock, flags);
>
> if (skb->protocol == htons(ETH_P_IP) && skb->ip_summed == CHECKSUM_PARTIAL)
> switch (skb->nh.iph->protocol) {
> @@ -742,7 +738,6 @@ spider_net_set_low_watermark(struct spid
> {
> struct spider_net_descr *descr = card->tx_chain.tail;
> struct spider_net_hw_descr *hwdescr;
> - unsigned long flags;
> int status;
> int cnt=0;
> int i;
> @@ -768,7 +763,6 @@ spider_net_set_low_watermark(struct spid
> descr = descr->next;
>
> /* Set the new watermark, clear the old watermark */
> - spin_lock_irqsave(&card->tx_chain.lock, flags);
> descr->hwdescr->dmac_cmd_status |= SPIDER_NET_DESCR_TXDESFLG;
> if (card->low_watermark && card->low_watermark != descr) {
> hwdescr = card->low_watermark->hwdescr;
> @@ -776,7 +770,7 @@ spider_net_set_low_watermark(struct spid
> hwdescr->dmac_cmd_status & ~SPIDER_NET_DESCR_TXDESFLG;
> }
> card->low_watermark = descr;
> - spin_unlock_irqrestore(&card->tx_chain.lock, flags);
> +
> return cnt;
> }
>
> @@ -784,6 +778,7 @@ spider_net_set_low_watermark(struct spid
> * spider_net_release_tx_chain - processes sent tx descriptors
> * @card: adapter structure
> * @brutal: if set, don't care about whether descriptor seems to be in use
> + * @locked: if set, tx_chain locked is held by caller.
> *
> * returns 0 if the tx ring is empty, otherwise 1.
> *
> @@ -793,7 +788,7 @@ spider_net_set_low_watermark(struct spid
> * scheduled again (if we were scheduled) and will not loose initiative.
> */
> static int
> -spider_net_release_tx_chain(struct spider_net_card *card, int brutal)
> +spider_net_release_tx_chain(struct spider_net_card *card, int brutal, int locked)
> {
> struct spider_net_descr_chain *chain = &card->tx_chain;
> struct spider_net_descr *descr;
> @@ -804,9 +799,11 @@ spider_net_release_tx_chain(struct spide
> int status;
>
> while (1) {
> - spin_lock_irqsave(&chain->lock, flags);
> + if (!locked)
> + spin_lock_irqsave(&chain->lock, flags);
> if (chain->tail == chain->head) {
> - spin_unlock_irqrestore(&chain->lock, flags);
> + if (!locked)
> + spin_unlock_irqrestore(&chain->lock, flags);
> return 0;
> }
> descr = chain->tail;
> @@ -821,7 +818,8 @@ spider_net_release_tx_chain(struct spide
>
> case SPIDER_NET_DESCR_CARDOWNED:
> if (!brutal) {
> - spin_unlock_irqrestore(&chain->lock, flags);
> + if (!locked)
> + spin_unlock_irqrestore(&chain->lock, flags);
> return 1;
> }
>
> @@ -842,7 +840,8 @@ spider_net_release_tx_chain(struct spide
> default:
> card->netdev_stats.tx_dropped++;
> if (!brutal) {
> - spin_unlock_irqrestore(&chain->lock, flags);
> + if (!locked)
> + spin_unlock_irqrestore(&chain->lock, flags);
> return 1;
> }
> }
> @@ -852,7 +851,9 @@ spider_net_release_tx_chain(struct spide
> skb = descr->skb;
> descr->skb = NULL;
> buf_addr = hwdescr->buf_addr;
> - spin_unlock_irqrestore(&chain->lock, flags);
> +
> + if (!locked)
> + spin_unlock_irqrestore(&chain->lock, flags);
>
> /* unmap the skb */
> if (skb) {
> @@ -916,18 +917,28 @@ spider_net_xmit(struct sk_buff *skb, str
> {
> int cnt;
> struct spider_net_card *card = netdev_priv(netdev);
> + unsigned long flags;
> +
> + if (!spin_trylock_irqsave(&card->tx_chain.lock, flags))
> + return NETDEV_TX_BUSY;
> + //? collision ? return NETDEV_TX_LOCKED;
>
> - spider_net_release_tx_chain(card, 0);
> + spider_net_release_tx_chain(card, 0, 1);
>
> if (spider_net_prepare_tx_descr(card, skb) != 0) {
> + spin_unlock_irqrestore(&card->tx_chain.lock, flags);
> card->netdev_stats.tx_dropped++;
> netif_stop_queue(netdev);
> return NETDEV_TX_BUSY;
> }
>
> cnt = spider_net_set_low_watermark(card);
> +
> + spin_unlock_irqrestore(&card->tx_chain.lock, flags);
> +
> if (cnt < 5)
> spider_net_kick_tx_dma(card);
> +
> return NETDEV_TX_OK;
> }
>
> @@ -943,11 +954,20 @@ spider_net_xmit(struct sk_buff *skb, str
> static void
> spider_net_cleanup_tx_ring(struct spider_net_card *card)
> {
> - if ((spider_net_release_tx_chain(card, 0) != 0) &&
> + unsigned long flags;
> +
> + if (!spin_trylock_irqsave(&card->tx_chain.lock, flags))
> + return;
> +
> + if ((spider_net_release_tx_chain(card, 0, 1) != 0) &&
> (card->netdev->flags & IFF_UP)) {
> + spin_unlock_irqrestore(&card->tx_chain.lock, flags);
> spider_net_kick_tx_dma(card);
> netif_wake_queue(card->netdev);
> - }
> + } else
> + spin_unlock_irqrestore(&card->tx_chain.lock, flags);
> +
> +
> }
>
> /**
> @@ -2092,7 +2112,7 @@ spider_net_stop(struct net_device *netde
> spider_net_disable_rxdmac(card);
>
> /* release chains */
> - spider_net_release_tx_chain(card, 1);
> + spider_net_release_tx_chain(card, 1, 0);
> spider_net_free_rx_chain_contents(card);
>
> spider_net_free_chain(card, &card->tx_chain);
>
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