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Date: Tue, 27 May 2008 13:49:44 +0800
From: "Luming Yu" <luming.yu@gmail.com>
To: "Roland McGrath" <roland@redhat.com>
Subject: Re: [RFC PATCH] set TASK_TRACED before arch_ptrace code to fix a race
Cc: "Petr Tesarik" <ptesarik@suse.cz>, LKML <linux-kernel@vger.kernel.org>,
       linux-ia64@vger.kernel.org
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>
>> It does happen!!
>
> Um.  Really?  What does happen exactly?

I revised patch a bit, and managed to get this:

Call Trace:
 [<a000000100011bd0>] show_stack+0x50/0xa0
                                sp=e000000141c9fbb0 bsp=e000000141c90ea8
 [<a000000100011c50>] dump_stack+0x30/0x60
                                sp=e000000141c9fd80 bsp=e000000141c90e90
 [<a000000100097a20>] get_signal_to_deliver+0xa0/0x720
                                sp=e000000141c9fd80 bsp=e000000141c90e28
 [<a0000001000343d0>] ia64_do_signal+0xb0/0xd00
                                sp=e000000141c9fd80 bsp=e000000141c90d78
 [<a000000100012650>] do_notify_resume_user+0xf0/0x140
                                sp=e000000141c9fe20 bsp=e000000141c90d48
 [<a00000010000aac0>] notify_resume_user+0x40/0x60
                                sp=e000000141c9fe20 bsp=e000000141c90cf8
 [<a00000010000a9f0>] skip_rbs_switch+0xe0/0x110
                                sp=e000000141c9fe30 bsp=e000000141c90cf8
 [<a000000000010740>] __kernel_syscall_via_break+0x0/0x20
                                sp=e000000141ca0000 bsp=e000000141c90cf8
 [<a0000001000971c0>] ptrace_stop+0xa0/0x3e0
                                sp=e00000014716fdb0 bsp=e000000147160ca8
 [<a000000100097650>] ptrace_notify+0x150/0x1c0
                                sp=e00000014716fdb0 bsp=e000000147160c88
 [<a00000010002adb0>] syscall_trace+0x30/0xc0
                                sp=e00000014716fe30 bsp=e000000147160c70
 [<a00000010002aea0>] syscall_trace_enter+0x60/0xa0
                                sp=e00000014716fe30 bsp=e000000147160c18
 [<a00000010000a300>] ia64_trace_syscall+0x40/0x110
                                sp=e00000014716fe30 bsp=e000000147160c18
 [<a000000000010740>] __kernel_syscall_via_break+0x0/0x20
                                sp=e000000147170000 bsp=e000000147160c18