On Thu, Mar 6, 2014 at 10:04 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Wed, 5 Mar 2014, Dave Jones wrote: > >> WARNING: CPU: 3 PID: 25477 at lib/dma-debug.c:593 debug_dma_assert_idle+0x1ba/0x223() >> uhci_hcd 0000:00:1d.2: DMA-API: cpu touching an active dma mapped cacheline [cln=0x0000000002355f80] >> Modules linked in: fuse tun l2tp_ppp l2tp_netlink l2tp_core can_raw can_bcm scsi_transport_iscsi nfc caif_socket caif af_802154 phonet af_rxrpc hidp bluetooth 6lowpan_iphc can pppoe pppox ppp_generic slhc irda crc_ccitt rds rose x25 atm netrom appletalk ipx p8023 p8022 psnap llc ax25 cfg80211 rfkill nouveau video backlight mxm_wmi wmi i2c_algo_bit ttm drm_kms_helper drm tg3 i2c_core ptp pps_core libphy kvm_intel kvm lpc_ich microcode pcspkr mfd_core parport_pc serio_raw parport shpchp rtc_cmos xfs libcrc32c raid0 floppy >> CPU: 3 PID: 25477 Comm: cc Not tainted 3.14.0-rc5+ #2 >> Hardware name: Dell Inc. Precision WorkStation 490 /0DT031, BIOS A08 04/25/2008 >> 00000000 2e7036e5 00000000 db851dbc c15f76ee db851dfc db851dec c1043733 >> c17ce4b0 db851e1c 00006385 c17ccc7a 00000251 c130a152 c130a152 eef3f650 >> efb53480 00000000 db851e08 c1043788 00000009 db851dfc c17ce4b0 db851e1c >> Call Trace: >> [<c15f76ee>] dump_stack+0x4b/0x75 >> [<c1043733>] warn_slowpath_common+0x7e/0x95 >> [<c130a152>] ? debug_dma_assert_idle+0x1ba/0x223 >> [<c130a152>] ? debug_dma_assert_idle+0x1ba/0x223 >> [<c1043788>] warn_slowpath_fmt+0x3e/0x51 >> [<c130a152>] debug_dma_assert_idle+0x1ba/0x223 >> [<c1159704>] do_wp_page+0x108/0x8a1 >> [<c115b790>] ? handle_mm_fault+0x1ba/0xd54 >> [<c15ff7ea>] ? _raw_spin_lock+0x6b/0x72 >> [<c115bae2>] handle_mm_fault+0x50c/0xd54 >> [<c160357c>] ? __do_page_fault+0xee/0x55c >> [<c16035da>] __do_page_fault+0x14c/0x55c >> [<c16039ea>] ? __do_page_fault+0x55c/0x55c >> [<c16039f7>] do_page_fault+0xd/0xf >> [<c1600dfc>] error_code+0x6c/0x74 >> ------------[ cut here ]------------ >> WARNING: CPU: 3 PID: 25490 at lib/dma-debug.c:593 debug_dma_assert_idle+0x1ba/0x223() >> uhci_hcd 0000:00:1d.2: DMA-API: cpu touching an active dma mapped cacheline [cln=0x0000000002355f80] >> ---[ end trace 3ac75acf24cf0b9e ]--- >> Mapped at: >> [<c13081b5>] debug_dma_alloc_coherent+0x2b/0xc3 >> Modules linked in: fuse tun l2tp_ppp l2tp_netlink l2tp_core can_raw can_bcm scsi_transport_iscsi nfc caif_socket caif af_802154 phonet af_rxrpc hidp bluetooth 6lowpan_iphc can pppoe pppox ppp_generic slhc irda crc_ccitt rds rose x25 atm netrom appletalk ipx p8023 p8022 psnap llc ax25 cfg80211 rfkill nouveau video backlight mxm_wmi wmi i2c_algo_bit ttm drm_kms_helper drm tg3 i2c_core ptp pps_core libphy kvm_intel kvm lpc_ich microcode pcspkr mfd_core parport_pc serio_raw parport shpchp rtc_cmos xfs libcrc32c raid0 floppy >> >> [<c116fcee>] dma_pool_alloc+0x14f/0x2fd >> [<c1456eaa>] uhci_alloc_td.isra.35+0x24/0x60 >> [<c1457fa6>] uhci_start+0x272/0x56b >> [<c142d8fb>] usb_add_hcd+0x252/0x774 >> >> CPU: 3 PID: 25490 Comm: cc Tainted: G W 3.14.0-rc5+ #2 >> Hardware name: Dell Inc. Precision WorkStation 490 /0DT031, BIOS A08 04/25/2008 >> 00000000 bf79585b 00000000 db81bdbc c15f76ee db81bdfc db81bdec c1043733 >> c17ce4b0 db81be1c 00006392 c17ccc7a 00000251 c130a152 c130a152 eef3f650 >> efb53480 00000000 db81be08 c1043788 00000009 db81bdfc c17ce4b0 db81be1c >> Call Trace: >> [<c15f76ee>] dump_stack+0x4b/0x75 >> [<c1043733>] warn_slowpath_common+0x7e/0x95 >> [<c130a152>] ? debug_dma_assert_idle+0x1ba/0x223 >> [<c130a152>] ? debug_dma_assert_idle+0x1ba/0x223 >> [<c1043788>] warn_slowpath_fmt+0x3e/0x51 >> [<c130a152>] debug_dma_assert_idle+0x1ba/0x223 >> [<c1159704>] do_wp_page+0x108/0x8a1 >> [<c115b790>] ? handle_mm_fault+0x1ba/0xd54 >> [<c15ff7ea>] ? _raw_spin_lock+0x6b/0x72 >> [<c115bae2>] handle_mm_fault+0x50c/0xd54 >> [<c160357c>] ? __do_page_fault+0xee/0x55c >> [<c16035da>] __do_page_fault+0x14c/0x55c >> [<c1603683>] ? __do_page_fault+0x1f5/0x55c >> [<c160065b>] ? restore_all+0xf/0xf >> [<c12f0d89>] ? __put_user_4+0x11/0x18 >> [<c16039ea>] ? __do_page_fault+0x55c/0x55c >> [<c16039f7>] do_page_fault+0xd/0xf >> [<c1600dfc>] error_code+0x6c/0x74 >> ---[ end trace 3ac75acf24cf0b9f ]--- >> Mapped at: >> [<c13081b5>] debug_dma_alloc_coherent+0x2b/0xc3 >> [<c116fcee>] dma_pool_alloc+0x14f/0x2fd >> [<c1456eaa>] uhci_alloc_td.isra.35+0x24/0x60 >> [<c1457fa6>] uhci_start+0x272/0x56b >> [<c142d8fb>] usb_add_hcd+0x252/0x774 > > I don't get it. As the name indicates, debug_dma_alloc_coherent should > give us consistent memory -- meaning that the CPU is allowed to access > the memory while DMA is in progress, without worrying about caching > effects (see Documentation/DMA-API.txt). > > So why should we get a warning when the CPU accesses this memory? Is > this a regression in the DMA debug library? Yes, it seems so. alloc_coherent needs to be exempt from active mapping tracking. Fix coming up. -- Dan -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
