Re: perf: fuzzer crashes immediately on AMD system

[Vince Weaver]

On Fri, 19 Aug 2016, Vince Weaver wrote:

> OK, this is weird.  I rebooted (didn't patch the kernel, just rebooted) 
> and I can't reproduce the original problem at all.

I rebooted three more times (after perf_fuzzer turned up a more boring 
probably known dump, shown at end) and now I am hitting the original bug 
again.   Weird.  Let me see if I can figure out what is going on.



and for the record, the bug the fuzzer kicks out when it doesn't hit the 
weird one:

note this is sprinkled among thousands of
[ 3782.364287] BAD LUCK: lost 7650 message(s) from NMI context!


[ 3780.821837] NMI watchdog: BUG: soft lockup - CPU#2 stuck for 23s! [perf_fuzzer:12074]
[ 3781.493831] CPU: 2 PID: 12074 Comm: perf_fuzzer Tainted: G             L  4.8.0-rc2+ #27
[ 3781.508478] Hardware name: Hewlett-Packard HP Compaq Pro 6305 SFF/1850, BIOS K06 v02.57 08/16/2013
[ 3781.524054] task: ffff8802232cf280 task.stack: ffff8802252c0000
[ 3781.542904] RIP: 0010:[<ffffffff810a1020>]  [<ffffffff810a1020>] smp_call_function_single+0xbb/0xca
[ 3781.558618] RSP: 0018:ffff8802252c3d78  EFLAGS: 00000202
[ 3781.570752] RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000
[ 3781.584757] RDX: 0000000000000001 RSI: 00000000000008fb RDI: 0000000000000300
[ 3781.598819] RBP: 0000000000000001 R08: 0000000000000003 R09: 00007f0c0ea07700
[ 3781.612930] R10: 00007f0c0ea079d0 R11: 0000000000000206 R12: ffffffff810e226b
[ 3781.627107] R13: ffff8802252c3dc8 R14: ffff8802252c3d78 R15: 0000000000000000
[ 3781.641335] FS:  00007f0c0ea07700(0000) GS:ffff88022ed00000(0000) knlGS:0000000000000000
[ 3781.656573] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 3781.669534] CR2: 00007f0c0e7d72c8 CR3: 00000002251d1000 CR4: 00000000000407e0
[ 3781.683929] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 3781.698410] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000010602
[ 3781.712845] Stack:
[ 3781.747577]  0000000000000000 ffffffff810e226b ffff8802252c3dc8 0000000000000003
[ 3781.787434]  ffffe8ffffc87190 ffff880223fb7800 ffffffff810e5676 0000000000000000
[ 3781.827415]  ffffffff810e18df ffffffff810e16cd 0000000000000000 ffffffff810e13d2
[ 3781.841792] Call Trace:
[ 3781.851292]  [<ffffffff810e226b>] ? perf_cgroup_attach+0x34/0x34
[ 3781.864355]  [<ffffffff810e5676>] ? group_sched_out+0x70/0x70
[ 3781.877219]  [<ffffffff810e18df>] ? event_function_call+0xa8/0xa8
[ 3781.890345]  [<ffffffff810e16cd>] ? cpu_function_call+0x32/0x3b
[ 3781.903284]  [<ffffffff810e13d2>] ? perf_ctx_lock+0x1e/0x1e
[ 3781.915864]  [<ffffffff810e1880>] ? event_function_call+0x49/0xa8
[ 3781.928952]  [<ffffffff810e5676>] ? group_sched_out+0x70/0x70
[ 3781.941675]  [<ffffffff810e18df>] ? event_function_call+0xa8/0xa8
[ 3781.954734]  [<ffffffff810e15a0>] ? perf_event_for_each_child+0x53/0x8a
[ 3781.968295]  [<ffffffff810e7bea>] ? perf_ioctl+0x41d/0x495
[ 3781.980725]  [<ffffffff811515f5>] ? vfs_ioctl+0x16/0x23
[ 3781.992893]  [<ffffffff81151ae3>] ? do_vfs_ioctl+0x46e/0x519
[ 3782.005532]  [<ffffffff81052aad>] ? do_sigaltstack+0xe1/0x1b0
[ 3782.018184]  [<ffffffff81151bdc>] ? SyS_ioctl+0x4e/0x71
[ 3782.030319]  [<ffffffff8145251f>] ? entry_SYSCALL_64_fastpath+0x17/0x93
[ 3782.433996] Code: e2 01 74 04 f3 90 eb f4 83 48 18 01 4c 89 e9 4c 89 e2 4c 89 f6 89 ef e8 94 fe ff ff 85 db 74 0d 41 8b 56 18 80 e2 01 74 04 f3 90 <eb> f3 48 83 c4 20 5b 5d 41 5c 41 5d 41 5e c3 41 56 41 55 41 89