Hello Sarah,
On Fri 11-10-13 15:13:15, Sarah Sharp wrote:
> I'm testing out some changes to the xHCI USB host controller driver
> (which uses a radix tree when a UAS device is attached to the host), and
> I noticed the following warning:
>
> Oct 11 14:42:08 xanatos kernel: [18165.819014] usb 2-2: new SuperSpeed USB
> device number 2 using xhci_hcd
> Oct 11 14:42:08 xanatos kernel: [18165.836264] usb 2-2: New USB device found,
> idVendor=174c, idProduct=55aa
> Oct 11 14:42:08 xanatos kernel: [18165.836271] usb 2-2: New USB device
> strings: Mfr=2, Product=3, SerialNumber=1
> Oct 11 14:42:08 xanatos kernel: [18165.836275] usb 2-2: Product: Plugable
> USB3-SATA-UASP1
> Oct 11 14:42:08 xanatos kernel: [18165.836279] usb 2-2: Manufacturer: ASM1053E
> Oct 11 14:42:08 xanatos kernel: [18165.836291] usb 2-2: SerialNumber:
> 123456789045
> Oct 11 14:42:08 xanatos kernel: [18165.847661] BUG: using smp_processor_id()
> in preemptible [00000000] code: modprobe/8759
> Oct 11 14:42:08 xanatos kernel: [18165.847667] caller is
> radix_tree_node_alloc+0x5c/0xa0
Well, this warning seems to come from the __get_cpu_var() function. I don't
see how my commit could have caused what you observe. It seems you are
calling radix_tree_insert() for a radix tree which has atomic gfp mask set
and you don't do radix_tree_preload() / radix_tree_preload_end() around
that? That was always problematic and could lead to the above warning.
I'm not sure in which contexts xhci_update_stream_ring() can be called. But
if you are guaranteed non-atomic context, then using radix_tree_preload()
with a more relaxed gfp mask is good (lowers pressure on atomic allocations).
If the context depends on the caller, things are more complex. Generally,
you can use radix_tree_maybe_preload() but you have to set gfp mask
argument according to the context. The function then figures out whether
it's worth it to do a preload or not (but it always does preempt_disable()
which will silence the warning).
Honza
> Oct 11 14:42:08 xanatos kernel: [18165.847670] CPU: 1 PID: 8759 Comm:
> modprobe Not tainted 3.12.0-rc4+ #94
> Oct 11 14:42:08 xanatos kernel: [18165.847671] Hardware name: LENOVO
> 2325AP7/2325AP7, BIOS G2ET82WW (2.02 ) 09/11/2012
> Oct 11 14:42:08 xanatos kernel: [18165.847673] ffff88010c1d3fd8
> ffff88010c1d38e8 ffffffff816081b9 0000000000000007
> Oct 11 14:42:08 xanatos kernel: [18165.847677] 0000000000000001
> ffff88010c1d3918 ffffffff812e3ffc ffff88010c26c988
> Oct 11 14:42:08 xanatos kernel: [18165.847679] 0000000000000020
> 00000000000240b1 0000000000000003 ffff88010c1d3938
> Oct 11 14:42:08 xanatos kernel: [18165.847682] Call Trace:
> Oct 11 14:42:08 xanatos kernel: [18165.847686] [<ffffffff816081b9>]
> dump_stack+0x4f/0x84
> Oct 11 14:42:08 xanatos kernel: [18165.847689] [<ffffffff812e3ffc>]
> debug_smp_processor_id+0xdc/0x100
> Oct 11 14:42:08 xanatos kernel: [18165.847692] [<ffffffff812d47fc>]
> radix_tree_node_alloc+0x5c/0xa0
> Oct 11 14:42:08 xanatos kernel: [18165.847695] [<ffffffff812d48d5>]
> radix_tree_insert+0x95/0x260
> Oct 11 14:42:08 xanatos kernel: [18165.847702] [<ffffffffa008446f>]
> xhci_update_stream_ring+0x8f/0xc0 [xhci_hcd]
> Oct 11 14:42:08 xanatos kernel: [18165.847708] [<ffffffffa00860f0>]
> xhci_alloc_stream_info+0x190/0x410 [xhci_hcd]
> Oct 11 14:42:08 xanatos kernel: [18165.847713] [<ffffffffa00802ef>]
> xhci_alloc_streams+0x36f/0x750 [xhci_hcd]
> Oct 11 14:42:08 xanatos kernel: [18165.847716] [<ffffffff8108678f>] ?
> ttwu_stat+0xef/0x160
> Oct 11 14:42:08 xanatos kernel: [18165.847720] [<ffffffff810c8e93>] ?
> is_module_address+0x33/0x60
> Oct 11 14:42:08 xanatos kernel: [18165.847729] [<ffffffffa0036e35>]
> usb_alloc_streams+0x95/0xb0 [usbcore]
> Oct 11 14:42:08 xanatos kernel: [18165.847732] [<ffffffffa01eb874>]
> uas_configure_endpoints+0x154/0x210 [uas]
> Oct 11 14:42:08 xanatos kernel: [18165.847735] [<ffffffffa01ec367>]
> uas_probe+0x2d7/0x390 [uas]
> Oct 11 14:42:08 xanatos kernel: [18165.847743] [<ffffffffa0040053>]
> usb_probe_interface+0x1c3/0x2f0 [usbcore]
> Oct 11 14:42:08 xanatos kernel: [18165.847746] [<ffffffff813ba421>]
> driver_probe_device+0x91/0x3c0
> Oct 11 14:42:08 xanatos kernel: [18165.847749] [<ffffffff813ba7fb>]
> __driver_attach+0xab/0xb0
> Oct 11 14:42:08 xanatos kernel: [18165.847751] [<ffffffff813ba750>] ?
> driver_probe_device+0x3c0/0x3c0
> Oct 11 14:42:08 xanatos kernel: [18165.847753] [<ffffffff813b835e>]
> bus_for_each_dev+0x5e/0x90
> Oct 11 14:42:08 xanatos kernel: [18165.847756] [<ffffffff813b9e6e>]
> driver_attach+0x1e/0x20
> Oct 11 14:42:08 xanatos kernel: [18165.847758] [<ffffffff813b988f>]
> bus_add_driver+0x10f/0x2d0
> Oct 11 14:42:08 xanatos kernel: [18165.847760] [<ffffffff813baf24>]
> driver_register+0x64/0xf0
> Oct 11 14:42:08 xanatos kernel: [18165.847767] [<ffffffffa003ec34>]
> usb_register_driver+0xc4/0x180 [usbcore]
> Oct 11 14:42:08 xanatos kernel: [18165.847770] [<ffffffffa01f0000>] ?
> 0xffffffffa01effff
> Oct 11 14:42:08 xanatos kernel: [18165.847773] [<ffffffffa01f001e>]
> uas_driver_init+0x1e/0x20 [uas]
> Oct 11 14:42:08 xanatos kernel: [18165.847775] [<ffffffff8100210a>]
> do_one_initcall+0xda/0x180
> Oct 11 14:42:08 xanatos kernel: [18165.847778] [<ffffffff81080313>] ?
> __blocking_notifier_call_chain+0x63/0x80
> Oct 11 14:42:08 xanatos kernel: [18165.847782] [<ffffffff810c7e42>]
> load_module+0x14b2/0x1ad0
> Oct 11 14:42:08 xanatos kernel: [18165.847784] [<ffffffff810c4680>] ?
> show_initstate+0x50/0x50
> Oct 11 14:42:08 xanatos kernel: [18165.847788] [<ffffffff810c8532>]
> SyS_init_module+0xd2/0x120
> Oct 11 14:42:08 xanatos kernel: [18165.847791] [<ffffffff816183a9>]
> system_call_fastpath+0x16/0x1b
>
> This looks possibly related to commit
> 5e4c0d974139a98741b829b27cf38dc8f9284490 "lib/radix-tree.c: make
> radix_tree_node_alloc() work correctly within interrupt". I'll revert
> the commit, and see if the warning disappears. In the meantime, can you
> look into fixing this?
>
> Thanks,
> Sarah Sharp
--
Jan Kara <j...@suse.cz>
SUSE Labs, CR
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