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Date: Sat, 16 Mar 2013 12:07:39 +0100 From: Christoph Paasch <christoph.paasch@...ouvain.be> To: Alexander Duyck <alexander.h.duyck@...el.com> Cc: Alexander Duyck <alexander.duyck@...il.com>, Jeff Kirsher <jeffrey.t.kirsher@...el.com>, Jesse Brandeburg <jesse.brandeburg@...el.com>, Bruce Allan <bruce.w.allan@...el.com>, Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org Subject: Re: igb_poll - device driver failed to check map error On Friday 15 March 2013 16:08:31 Alexander Duyck wrote: > On 03/15/2013 12:52 AM, Christoph Paasch wrote: > > On Thursday 14 March 2013 19:18:18 Alexander Duyck wrote: > >> On 03/12/2013 02:31 AM, Christoph Paasch wrote: > >>> Hello, > >>> > >>> I'm seeing a warning while booting my machine when DMA_API_DEBUG is set: > >>> > >>> [ 36.402824] ------------[ cut here ]------------ > >>> [ 36.458070] WARNING: at > >>> /home/cpaasch/builder/net-next/lib/dma-debug.c:934 > >>> check_unmap+0x648/0x702() > >>> [ 36.567377] Hardware name: ProLiant DL165 G7 > >>> [ 36.618452] igb 0000:04:00.0: DMA-API: device driver failed to check > >>> map > >>> error[device address=0x0000000233d9b232] [size=154 bytes] [mapped as > >>> single] [ 36.776640] Modules linked in: > >>> [ 36.815446] Pid: 0, comm: swapper/7 Not tainted 3.9.0-rc1-mptcp+ #101 > >>> [ 36.892515] Call Trace: > >>> [ 36.921745] <IRQ> [<ffffffff8102ad7f>] > >>> warn_slowpath_common+0x80/0x9a > >>> [ 37.001023] [<ffffffff8102ae2d>] warn_slowpath_fmt+0x41/0x43 > >>> [ 37.069771] [<ffffffff811db17f>] check_unmap+0x648/0x702 > >>> [ 37.134363] [<ffffffff811db3e9>] debug_dma_unmap_page+0x50/0x52 > >>> [ 37.206234] [<ffffffff8136676a>] igb_poll+0x144/0xf7c > >>> [ 37.267706] [<ffffffff8104dd19>] ? sched_clock_cpu+0x46/0xd1 > >>> [ 37.336456] [<ffffffff814458ce>] net_rx_action+0xa7/0x1d0 > >>> [ 37.402085] [<ffffffff81030b65>] __do_softirq+0xb4/0x16f > >>> [ 37.466673] [<ffffffff81030c90>] irq_exit+0x40/0x87 > >>> [ 37.526067] [<ffffffff81002db1>] do_IRQ+0x98/0xaf > >>> [ 37.583378] [<ffffffff815210aa>] common_interrupt+0x6a/0x6a > >>> [ 37.651086] <EOI> [<ffffffff8105d4be>] ? > >>> __tick_nohz_idle_enter+0x116/0x31f > >>> [ 37.736595] [<ffffffff81008a04>] ? default_idle+0x24/0x39 > >>> [ 37.802224] [<ffffffff81008c62>] cpu_idle+0x68/0xa4 > >>> [ 37.861616] [<ffffffff81519f78>] start_secondary+0x1a9/0x1ad > >>> [ 37.930364] ---[ end trace 01b5bb0fd75a464c ]--- > >>> > >>> > >>> It happens shortly after mounting the NFS-root filesystem. > >>> > >>> I tried to understand what is going on, but I am now at my wit's end. > >>> > >>> By adding some print-statements, here is what I found out (not sure if > >>> this is anyhow helpful): > >>> > >>> The difference between tx_buffer->time_stamp and the current 'jiffies' > >>> is > >>> up to 2000 jiffies (HZ==1000) at the first time the above warning > >>> happens > >>> (this seems too much for me). From then on, I see my print 3-4 times > >>> appear but without such a big difference between the timestamps > >>> (difference around 1 and 2 jiffies). > >>> > >>> Some other stuff, I printed: > >>> tx_buffer->skb: ffff880235054c80 > >>> tx_buffer->bytecount: 154 > >>> tx_buffer->gso_segs: 1 > >>> tx_buffer->protocol: 8 > >>> tx_buffer->tx_flags 0x20 > >>> > >>> > >>> One last thing: > >>> Am I right that after each call to dma_map_single/page a call to > >>> dma_mapping_error is needed? If that's the case, I have some patches > >>> that > >>> add this statement at missing places in the e1000, e1000e and ixgb > >>> driver. But these patches do not fix my above problem. > >>> > >>> > >>> Thanks for your help, > >>> Christoph > >> > >> Christoph, > >> > >> One thing that might be useful would be to reproduce this with a > >> standard 3.9-rc kernel instead of one using the multipath TCP patches. > >> This will help us to verify that the issue is reproducible with a stock > >> kernel and is not related to any ongoing work you may have only in your > >> tree. > > > > Hello, > > > > this is on a clean net-next kernel without any MPTCP-code. > > > > I bisected it down to 787314c35fbb (Merge tag 'iommu-updates-v3.8' of > > git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu), which simply > > introduces the debug_dma_mapping_error-checks. > > > > Am I right with the missing calls to dma_mapping_error in e1000, e1000e > > and > > ixgb? > > > > Cheers, > > Christoph > > Christoph, > > The cause of this issues you are seeing may be due to the fact that the > buffer triggering the error is being reused. I was able to reproduce > this issue occasionally with pktgen if I cloned the skb. What may be > happening is that the buffer is being mapped in the transmit path on one > CPU while on another CPU the buffer is being cleaned. Since the output > of each mapping is the physical address there is nothing to make each > mapping unique and I suspect this is resulting in false hits. > > You should be able to verify this if you were to check the skb->users > count as well as the dataref value in the skb_shared_info. I suspect > either the users count of the dataref will be greater than 1. Both, users and dataref, are equal to 1. Before the call to dev_kfree_skb_any and after dma_unmap_single fails. > You might also try testing the patch below to see if it has any effect. > All it does is reorder the free and the unmap so that the buffer is not > freed for reuse until after we have checked it in the unmap path. I tested your patch, and it fixes my issue. Feel free to add a "Tested-by" to the official patch. Cheers, Christoph > --- > drivers/net/ethernet/intel/igb/igb_main.c | 6 +++--- > 1 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/ethernet/intel/igb/igb_main.c > b/drivers/net/ethernet/intel/igb/igb_main.c > index 4dbd629..0f9c324 100644 > --- a/drivers/net/ethernet/intel/igb/igb_main.c > +++ b/drivers/net/ethernet/intel/igb/igb_main.c > @@ -5959,15 +5959,15 @@ static bool igb_clean_tx_irq(struct igb_q_vector > *q_vector) > total_bytes += tx_buffer->bytecount; > total_packets += tx_buffer->gso_segs; > > - /* free the skb */ > - dev_kfree_skb_any(tx_buffer->skb); > - > /* unmap skb header data */ > dma_unmap_single(tx_ring->dev, > dma_unmap_addr(tx_buffer, dma), > dma_unmap_len(tx_buffer, len), > DMA_TO_DEVICE); > > + /* free the skb */ > + dev_kfree_skb_any(tx_buffer->skb); > + > /* clear tx_buffer data */ > tx_buffer->skb = NULL; > dma_unmap_len_set(tx_buffer, len, 0); -- IP Networking Lab --- http://inl.info.ucl.ac.be MultiPath TCP in the Linux Kernel --- http://multipath-tcp.org UCLouvain -- -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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