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Date: Tue, 27 Oct 2015 04:24:35 -0400
From: Dave Jones <davej@codemonkey.org.uk>
To: Linux Kernel <linux-kernel@vger.kernel.org>
Cc: vincent.weaver@maine.edu
Subject: perf oops/recursive fault using BTS
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I was experimenting with a variant of Vince's bts_kernel test
(https://github.com/deater/perf_event_tests/blob/master/tests/x86_intel/bts_kernel.c)
and hit this..

Oops: 0000 [#1] PREEMPT SMP 
CPU: 3 PID: 2471 Comm: a.out Not tainted 4.3.0-rc6-wopr+ #1 
task: ffff8805f0b3e400 ti: ffff8801f81d4000 task.ti: ffff8801f81d4000
RIP: 0010:[<ffffffff9d13e44c>]  [<ffffffff9d13e44c>] perf_mmap_close+0x3c/0x250
RSP: 0000:ffff8801f81d7b78  EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 000000000952ecf3 RSI: ffff88082fc78ea0 RDI: ffff8808026de800
RBP: ffff8801f81d7bc8 R08: 0000000000018ea0 R09: ffff88080c201000
R10: ffffea00151ae460 R11: 0000000000000000 R12: ffff8807071d2000
R13: ffff8808026de800 R14: ffff8807071d2678 R15: ffff8805f0b3e400
FS:  0000000000000000(0000) GS:ffff88082fc60000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000000c0 CR3: 000000001dc0b000 CR4: 00000000001406e0
Stack:
 ffff8801f81d7c00 ffff8805f0b3e9f8 ffff8807ed482de8 ffff8805f0b3e400
 00000000c88a8a46 ffff8807071d2678 ffff8807071d2000 ffff8805f0b3e9f8
 ffff8807ed482de8 ffff8805f0b3e400 ffff8801f81d7be8 ffffffff9d17852a
Call Trace:
 [<ffffffff9d17852a>] remove_vma+0x2a/0x60
 [<ffffffff9d17bdfd>] exit_mmap+0x12d/0x160
 [<ffffffff9d07040f>] mmput+0x4f/0xf0
 [<ffffffff9d07458e>] do_exit+0x31e/0xaa0
 [<ffffffff9d075b53>] do_group_exit+0x43/0xb0
 [<ffffffff9d080deb>] get_signal+0x23b/0x640
 [<ffffffff9d003b97>] do_signal+0x37/0x6b0
 [<ffffffff9d03e306>] ? force_sig_info_fault.constprop.23+0x76/0x90
 [<ffffffff9d090000>] ? kthread_bind+0x40/0x40
 [<ffffffff9d03e356>] ? is_prefetch.isra.18+0x36/0x260
 [<ffffffff9d090000>] ? kthread_bind+0x40/0x40
 [<ffffffff9d03eeb0>] ? mm_fault_error+0x110/0x130
 [<ffffffff9d03f30a>] ? __do_page_fault+0x43a/0x470
 [<ffffffff9d001b06>] prepare_exit_to_usermode+0xb6/0x110
 [<ffffffff9d6c76ea>] retint_user+0x8/0x1d
Code: 83 ec 28 65 48 8b 04 25 28 00 00 00 48 89 45 d0 31 c0 48 8b 87 a0 00 00 00 4c 8b a8 c8 00 00 00 4c 89 ef e8 57 ec ff ff 48 89 c3 <48> 8b 80 c0 00 00 00 48 89 45 c0 48 8b 83 b8 00 00 00 48 89 45 
RIP  [<ffffffff9d13e44c>] perf_mmap_close+0x3c/0x250
 RSP <ffff8801f81d7b78>
CR2: 00000000000000c0
---[ end trace 9362dce880c51b19 ]---
Fixing recursive fault but reboot is needed!