Recent 4.8 kernels have been oopsing when running under VMWare:
[ 2.270203] BUG: unable to handle kernel NULL pointer dereference at
0000000000000408
[ 2.270325] IP: [<ffffffff81012bb9>] rapl_cpu_online+0x59/0x70
[ 2.270448] PGD 0
[ 2.270570] Oops: 0002 [#1] SMP
[ 2.270693] Modules linked in:
[ 2.270815] CPU: 2 PID: 21 Comm: cpuhp/2 Not tainted 4.8.2-1-amd64-vyatta #1
[ 2.270938] Hardware name: VMware, Inc. VMware Virtual Platform/440BX
Desktop Reference Platform, BIOS 6.00 04/14/2014
[ 2.271060] task: ffff8802361fc2c0 task.stack: ffff880236208000
[ 2.271183] RIP: 0010:[<ffffffff81012bb9>] [<ffffffff81012bb9>]
rapl_cpu_online+0x59/0x70
[ 2.271306] RSP: 0000:ffff88023620be68 EFLAGS: 00010246
[ 2.271428] RAX: 0000000000000004 RBX: ffff88023fd0d940 RCX: 0000000000000000
[ 2.271551] RDX: 0000000000000040 RSI: 0000000000000004 RDI: 0000000000000004
[ 2.271673] RBP: 0000000000000002 R08: fffffffffffffffc R09: 0000000000000000
[ 2.271796] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000400
[ 2.271918] R13: ffff8802361fc2c0 R14: ffff8802361fc2c0 R15: ffff8802361fc2c0
[ 2.272041] FS: 0000000000000000(0000) GS:ffff88023fd00000(0000)
knlGS:0000000000000000
[ 2.272163] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 2.272286] CR2: 0000000000000408 CR3: 0000000001a06000 CR4: 00000000000406e0
[ 2.272408] Stack:
[ 2.272531] ffff88023fd0d940 0000000000000002 ffffffff81a38240
ffffffff81061231
[ 2.272654] ffff8802361fc2c0 ffff880237002180 ffffffff8107ddcf
0000000000000000
[ 2.272776] ffff8802361a5a80 ffff880237002180 ffffffff8107dcb0
ffffffff81a6a380
[ 2.272899] Call Trace:
[ 2.273021] [<ffffffff81061231>] ? cpuhp_thread_fun+0x31/0x100
[ 2.273144] [<ffffffff8107ddcf>] ? smpboot_thread_fn+0x11f/0x180
[ 2.273266] [<ffffffff8107dcb0>] ? sort_range+0x20/0x20
[ 2.273389] [<ffffffff8107b05a>] ? kthread+0xca/0xe0
[ 2.273511] [<ffffffff8157677f>] ? ret_from_fork+0x1f/0x40
[ 2.273634] [<ffffffff8107af90>] ? kthread_park+0x50/0x50
[ 2.273757] Code: 00 00 48 83 c0 22 4c 8b 24 c1 48 c7 c0 30 a1 00 00 48 8b
14 10 e8 a8 61 26 00 3b 05 b6 56 ae 00 7c 0e f0 48 0f a
[ 2.279445] RIP [<ffffffff81012bb9>] rapl_cpu_online+0x59/0x70
[ 2.279568] RSP <ffff88023620be68>
[ 2.279690] CR2: 0000000000000408
[ 2.279813] ---[ end trace c95da920748eb432 ]---
gdb tells me:
(gdb) info line *(rapl_cpu_online+0x59)
Line 595 of "arch/x86/events/intel/rapl.c" starts at address 0xffffffff81012bb9
<rapl_cpu_online+89>
and ends at 0xffffffff81012bbe <rapl_cpu_online+94>.
Which is:
target = cpumask_any_and(&rapl_cpu_mask, topology_core_cpumask(cpu));
if (target < nr_cpu_ids)
return 0;
cpumask_set_cpu(cpu, &rapl_cpu_mask);
pmu->cpu = cpu; <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
return 0;
This code was recently changed by commit 8b5b773d6245138c
"perf/x86/intel/rapl: Convert to hotplug state machine" and it
appears that the setup is done as a callback:
/*
* Install callbacks. Core will call them for each online cpu.
*/
ret = cpuhp_setup_state(CPUHP_PERF_X86_RAPL_PREP, "PERF_X86_RAPL_PREP",
rapl_cpu_prepare, NULL);
if (ret)
goto out;
ret = cpuhp_setup_state(CPUHP_AP_PERF_X86_RAPL_ONLINE,
"AP_PERF_X86_RAPL_ONLINE",
rapl_cpu_online, rapl_cpu_offline);
Is there a particular order guaranteed by the callbacks? Will
rapl_cpu_prepare() always happen before online/offline? Additionally,
rapl_cpu_prepare() can fail to allocate pmu,
static int rapl_cpu_prepare(unsigned int cpu)
{
struct rapl_pmu *pmu = cpu_to_rapl_pmu(cpu);
if (pmu)
return 0;
pmu = kzalloc_node(sizeof(*pmu), GFP_KERNEL, cpu_to_node(cpu));
if (!pmu)
return -ENOMEM;
But rapl_cpu_online() would have no idea about this. What should be
done in this case?
