Hello

> With 3.0.0 the PAPI "overflow_allcounters" test reliably locks up my 
> Nehalem system.

I finally managed to narrow this down to a small test, which is attached.

Basically measuring overflow on the perf::perf_count_sw_cpu_clock
event will potentially *lock up* your system from user-space.

This seems to be a long standing bug.  It will quickly lock solid
my Nehalem test box on 3.0, 2.6.39 and 2.6.38.

On a Core2 2.6.32 box the crash testing program will wedge and become 
unkillable, but it doesn't actually kill the machine.

As mentioned before, on the Nehalem machine the following warning happens
before the machine becomes unusable:

[  392.504845] ------------[ cut here ]------------
[  392.504962] WARNING: at kernel/smp.c:320 smp_call_function_single+0x6c/0xf2()
[  392.505074] Hardware name: Precision M4500
[  392.505181] Modules linked in: acpi_cpufreq cpufreq_conservative mperf cpufreq_powersave cpufreq_userspace cpufreq_stats uinput nouveau snd_hda_codec_hdmi ttm drm_kms_helper mxm_wmi snd_hda_codec_idt iwlagn mac80211 snd_hda_intel snd_hda_codec cfg80211 dell_laptop snd_hwdep video processor ehci_hcd dell_wmi sparse_keymap psmouse sdhci_pci rfkill snd_pcm sdhci thermal_sys pcspkr ac battery wmi serio_raw snd_timer snd_page_alloc evdev i2c_i801 dcdbas button
[  392.509709] Pid: 2310, comm: overflow_allcou Not tainted 3.0.0 #43
[  392.509819] Call Trace:
[  392.509925]  <IRQ>  [<ffffffff81041bb0>] ? warn_slowpath_common+0x78/0x8c
[  392.510144]  [<ffffffff810a4d19>] ? perf_exclude_event.part.23+0x31/0x31
[  392.510257]  [<ffffffff8106b7c5>] ? smp_call_function_single+0x6c/0xf2
[  392.510369]  [<ffffffff810a38aa>] ? task_function_call+0x42/0x4c
[  392.510476]  [<ffffffff810a50e4>] ? update_cgrp_time_from_event+0x2c/0x2c
[  392.510589]  [<ffffffff810a5a9d>] ? perf_event_disable+0x45/0x8c
[  392.510700]  [<ffffffff810a8e89>] ? __perf_event_overflow+0xf1/0x1a3
[  392.510812]  [<ffffffff8103c7bb>] ? select_task_rq_fair+0x349/0x574
[  392.510924]  [<ffffffff810a7f0a>] ? perf_ctx_adjust_freq+0x42/0xe6
[  392.511038]  [<ffffffff8105f152>] ? sched_clock_cpu+0xb/0xc3
[  392.511152]  [<ffffffff8100ded5>] ? paravirt_read_tsc+0x5/0x8
[  392.511262]  [<ffffffff8100e320>] ? native_sched_clock+0x27/0x2f
[  392.511366]  [<ffffffff810a9500>] ? perf_event_overflow+0x10/0x10
[  392.511476]  [<ffffffff810a959f>] ? perf_swevent_hrtimer+0x9f/0xda
[  392.511599]  [<ffffffff8105ca04>] ? run_posix_cpu_timers+0x23/0x346
[  392.511721]  [<ffffffff8131c2ef>] ? rb_insert_color+0xb1/0xd9
[  392.511841]  [<ffffffff8105d373>] ? __run_hrtimer+0xac/0x135
[  392.511960]  [<ffffffff8105daa3>] ? hrtimer_interrupt+0xdb/0x195
[  392.512083]  [<ffffffff8108d040>] ? check_for_new_grace_period.isra.32+0x99/0xa4
[  392.512220]  [<ffffffff8108d201>] ? __rcu_process_callbacks+0x72/0x2b7
[  392.512345]  [<ffffffff8102437c>] ? hpet_interrupt_handler+0x23/0x2b
[  392.512469]  [<ffffffff81089446>] ? handle_irq_event_percpu+0x50/0x180
[  392.512592]  [<ffffffff81046f76>] ? __do_softirq+0x13e/0x177
[  392.512713]  [<ffffffff810f680c>] ? send_sigio+0x95/0xab
[  392.512832]  [<ffffffff810895aa>] ? handle_irq_event+0x34/0x52
[  392.512952]  [<ffffffff8108b433>] ? handle_edge_irq+0x9f/0xc6
[  392.513072]  [<ffffffff8100a831>] ? handle_irq+0x1d/0x21
[  392.513192]  [<ffffffff8100a561>] ? do_IRQ+0x42/0x98
[  392.513314]  [<ffffffff81593053>] ? common_interrupt+0x13/0x13
[  392.513438]  <EOI> 
[  392.513542] ---[ end trace 12f3f913316a2866 ]---

Thanks,

Vince