Re: [PATCH] x86: Remove WARN_ON(in_nmi()) from vmalloc_fault

From: Steven Rostedt
Date: Wed Oct 16 2013 - 08:42:28 EST

On Wed, 16 Oct 2013 08:11:18 +0200
Ingo Molnar <mingo@xxxxxxxxxx> wrote:

>
> * Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> > Since the NMI iretq nesting has been fixed, there's no reason that
> > an NMI handler can not take a page fault for vmalloc'd code. No locks
> > are taken in that code path, and the software now handles nested NMIs
> > when the fault re-enables NMIs on iretq.
> >
> > Not only that, if the vmalloc_fault() WARN_ON_ONCE() is hit, and that
> > warn on triggers a vmalloc fault for some reason, then we can go into
> > an infinite loop (the WARN_ON_ONCE() does the WARN() before updating
> > the variable to make it happen "once").
> >
> > Reported-by: "Liu, Chuansheng" <chuansheng.liu@xxxxxxxxx>
> > Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
>
> Would be nice to see the warning quoted that triggered this.

Sure, want me to add this to the change log?

===============
[ 15.069144] BUG: unable to handle kernel [ 15.073635] paging request at 1649736d
[ 15.076379] IP: [<c200402a>] print_context_stack+0x4a/0xa0
[ 15.082529] *pde = 00000000
[ 15.085758] Thread overran stack, or stack corrupted
[ 15.091303] Oops: 0000 [#1] SMP
[ 15.094932] Modules linked in: atomisp_css2400b0_v2(+) lm3554 ov2722 imx1x5 atmel_mxt_ts vxd392 videobuf_vmalloc videobuf_core bcm_bt_lpm bcm43241 kct_daemon(O)
[ 15.111093] CPU: 2 PID: 2443 Comm: Compiler Tainted: G W O 3.10.1+ #1
[ 15.119075] task: f213f980 ti: f0c42000 task.ti: f0c42000
[ 15.125116] EIP: 0060:[<c200402a>] EFLAGS: 00210087 CPU: 2
[ 15.131255] EIP is at print_context_stack+0x4a/0xa0
[ 15.136712] EAX: 16497ffc EBX: 1649736d ECX: 986736d8 EDX: 1649736d
[ 15.143722] ESI: 00000000 EDI: ffffe000 EBP: f0c4220c ESP: f0c421ec
[ 15.150732] DS: 007b ES: 007b FS: 00d8 GS: 003b SS: 0068
[ 15.156771] CR0: 80050033 CR2: 1649736d CR3: 31245000 CR4: 001007d0
[ 15.163781] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
[ 15.170789] DR6: ffff0ff0 DR7: 00000400
[ 15.175076] Stack:
[ 15.177324] 16497ffc 16496000 986736d8 ffffe000 986736d8 1649736d c282c148 16496000
[ 15.186067] f0c4223c c20033b0 c282c148 c29ceecf 00000000 f0c4222c 986736d8 f0c4222c
[ 15.194810] 00000000 c29ceecf 00000000 00000000 f0c42260 c20041a7 f0c4229c c282c148
[ 15.203549] Call Trace:
[ 15.206295] [<c20033b0>] dump_trace+0x70/0xf0
[ 15.211274] [<c20041a7>] show_trace_log_lvl+0x47/0x60
[ 15.217028] [<c2003482>] show_stack_log_lvl+0x52/0xd0
[ 15.222782] [<c2004201>] show_stack+0x21/0x50
[ 15.227762] [<c281b38b>] dump_stack+0x16/0x18
[ 15.232742] [<c2037cff>] warn_slowpath_common+0x5f/0x80
[ 15.238693] [<c282553a>] ? vmalloc_fault+0x5a/0xcf
[ 15.244156] [<c282553a>] ? vmalloc_fault+0x5a/0xcf
[ 15.249621] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 15.255472] [<c2037d3d>] warn_slowpath_null+0x1d/0x20
[ 15.261228] [<c282553a>] vmalloc_fault+0x5a/0xcf
[ 15.266497] [<c282592f>] __do_page_fault+0x2cf/0x4a0
[ 15.272154] [<c25e13e0>] ? logger_aio_write+0x230/0x230
[ 15.278106] [<c2039c94>] ? console_unlock+0x314/0x440
... //
[ 16.885364] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 16.891217] [<c2825b08>] do_page_fault+0x8/0x10
[ 16.896387] [<c2823066>] error_code+0x5a/0x60
[ 16.901367] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 16.907219] [<c208d6a0>] ? print_modules+0x20/0x90
[ 16.912685] [<c2037cfa>] warn_slowpath_common+0x5a/0x80
[ 16.918634] [<c282553a>] ? vmalloc_fault+0x5a/0xcf
[ 16.924097] [<c282553a>] ? vmalloc_fault+0x5a/0xcf
[ 16.929562] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 16.935415] [<c2037d3d>] warn_slowpath_null+0x1d/0x20
[ 16.941169] [<c282553a>] vmalloc_fault+0x5a/0xcf
[ 16.946437] [<c282592f>] __do_page_fault+0x2cf/0x4a0
[ 16.952095] [<c25e13e0>] ? logger_aio_write+0x230/0x230
[ 16.958046] [<c2039c94>] ? console_unlock+0x314/0x440
[ 16.963800] [<c2003e62>] ? sys_modify_ldt+0x2/0x160
[ 16.969362] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 16.975215] [<c2825b08>] do_page_fault+0x8/0x10
[ 16.980386] [<c2823066>] error_code+0x5a/0x60
[ 16.985366] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 16.991215] [<c208d6a0>] ? print_modules+0x20/0x90
[ 16.996673] [<c2037cfa>] warn_slowpath_common+0x5a/0x80
[ 17.002622] [<c282553a>] ? vmalloc_fault+0x5a/0xcf
[ 17.008086] [<c282553a>] ? vmalloc_fault+0x5a/0xcf
[ 17.013550] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 17.019403] [<c2037d3d>] warn_slowpath_null+0x1d/0x20
[ 17.025159] [<c282553a>] vmalloc_fault+0x5a/0xcf
[ 17.030428] [<c282592f>] __do_page_fault+0x2cf/0x4a0
[ 17.036085] [<c25e13e0>] ? logger_aio_write+0x230/0x230
[ 17.042037] [<c2039c94>] ? console_unlock+0x314/0x440
[ 17.047790] [<c2003e62>] ? sys_modify_ldt+0x2/0x160
[ 17.053352] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 17.059205] [<c2825b08>] do_page_fault+0x8/0x10
[ 17.064375] [<c2823066>] error_code+0x5a/0x60
[ 17.069354] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 17.075204] [<c208d6a0>] ? print_modules+0x20/0x90
[ 17.080669] [<c2037cfa>] warn_slowpath_common+0x5a/0x80
[ 17.086619] [<c282553a>] ? vmalloc_fault+0x5a/0xcf
[ 17.092082] [<c282553a>] ? vmalloc_fault+0x5a/0xcf
[ 17.097546] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 17.103399] [<c2037d3d>] warn_slowpath_null+0x1d/0x20
[ 17.109154] [<c282553a>] vmalloc_fault+0x5a/0xcf
[ 17.114422] [<c282592f>] __do_page_fault+0x2cf/0x4a0
[ 17.120080] [<c206b93d>] ? update_group_power+0x1fd/0x240
[ 17.126224] [<c227827b>] ? number.isra.2+0x32b/0x330
[ 17.131880] [<c20679bc>] ? update_curr+0xac/0x190
[ 17.137247] [<c227827b>] ? number.isra.2+0x32b/0x330
[ 17.142905] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 17.148755] [<c2825b08>] do_page_fault+0x8/0x10
[ 17.153926] [<c2823066>] error_code+0x5a/0x60
[ 17.158905] [<c2825b00>] ? __do_page_fault+0x4a0/0x4a0
[ 17.164760] [<c208d1a9>] ? module_address_lookup+0x29/0xb0
[ 17.170999] [<c208dddb>] kallsyms_lookup+0x9b/0xb0
[ 17.176462] [<c208de1d>] __sprint_symbol+0x2d/0xd0
[ 17.181926] [<c22790cc>] ? sprintf+0x1c/0x20
[ 17.186804] [<c208def4>] sprint_symbol+0x14/0x20
[ 17.192063] [<c208df1e>] __print_symbol+0x1e/0x40
[ 17.197430] [<c25e00d7>] ? ashmem_shrink+0x77/0xf0
[ 17.202895] [<c25e13e0>] ? logger_aio_write+0x230/0x230
[ 17.208845] [<c205bdf5>] ? up+0x25/0x40
[ 17.213242] [<c2039cb7>] ? console_unlock+0x337/0x440
[ 17.218998] [<c2818236>] ? printk+0x38/0x3a
[ 17.223782] [<c20006d0>] __show_regs+0x70/0x190
[ 17.228954] [<c200353a>] show_regs+0x3a/0x1b0
[ 17.233931] [<c2818236>] ? printk+0x38/0x3a
[ 17.238717] [<c2824182>] arch_trigger_all_cpu_backtrace_handler+0x62/0x80
[ 17.246413] [<c2823919>] nmi_handle.isra.0+0x39/0x60
[ 17.252071] [<c2823a29>] do_nmi+0xe9/0x3f0

-- Steve
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