Messages in this thread | | | Date | Tue, 24 Oct 2023 11:04:06 -0500 | Subject | Re: [PATCH 2/2] perf/x86/amd: Don't allow pre-emption in amd_pmu_lbr_reset() | From | Mario Limonciello <> |
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On 10/24/2023 10:59, Peter Zijlstra wrote: > On Tue, Oct 24, 2023 at 10:32:27AM -0500, Mario Limonciello wrote: >> On 10/24/2023 03:02, Ingo Molnar wrote: >>> >>> * Mario Limonciello <mario.limonciello@amd.com> wrote: >>> >>>> Fixes a BUG reported during suspend to ram testing. >>>> >>>> ``` >>>> [ 478.274752] BUG: using smp_processor_id() in preemptible [00000000] code: rtcwake/2948 >>>> [ 478.274754] caller is amd_pmu_lbr_reset+0x19/0xc0 >>>> ``` >>>> >>>> Cc: stable@vger.kernel.org # 6.1+ >>>> Fixes: ca5b7c0d9621 ("perf/x86/amd/lbr: Add LbrExtV2 branch record support") >>>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> >>>> --- >>>> arch/x86/events/amd/lbr.c | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/arch/x86/events/amd/lbr.c b/arch/x86/events/amd/lbr.c >>>> index eb31f850841a..5b98e8c7d8b7 100644 >>>> --- a/arch/x86/events/amd/lbr.c >>>> +++ b/arch/x86/events/amd/lbr.c >>>> @@ -321,7 +321,7 @@ int amd_pmu_lbr_hw_config(struct perf_event *event) >>>> void amd_pmu_lbr_reset(void) >>>> { >>>> - struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); >>>> + struct cpu_hw_events *cpuc = get_cpu_ptr(&cpu_hw_events); >>>> int i; >>>> if (!x86_pmu.lbr_nr) >>>> @@ -335,6 +335,7 @@ void amd_pmu_lbr_reset(void) >>>> cpuc->last_task_ctx = NULL; >>>> cpuc->last_log_id = 0; >>>> + put_cpu_ptr(&cpu_hw_events); >>>> wrmsrl(MSR_AMD64_LBR_SELECT, 0); >>>> } >>> >>> Weird, amd_pmu_lbr_reset() is called from these places: >>> >>> - amd_pmu_lbr_sched_task(): during task sched-in during >>> context-switching, this should already have preemption disabled. >>> >>> - amd_pmu_lbr_add(): this gets indirectly called by amd_pmu::add >>> (amd_pmu_add_event()), called by event_sched_in(), which too should have >>> preemption disabled. >>> >>> I clearly must have missed some additional place it gets called in. >>> >>> Could you please cite the full log of the amd_pmu_lbr_reset() call that >>> caused the critical section warning? >>> >>> Thanks, >>> >>> Ingo >> >> Below is the call trace in case you think it's better to disable preemption >> by the caller instead. If you think it's better to keep it in >> amd_pmu_lbr_reset() I'll add this trace to the commit message. > > You cut too much; what task is running this? > > IIRC this is the hotplug thread running a teardown function on that CPU > itself. It being a strict per-cpu thread should not trip > smp_processor_id() wanrs. >
BUG: using smp_processor_id() in preemptible [00000000] code: rtcwake/2960 caller is amd_pmu_lbr_reset+0x19/0xc0 CPU: 104 PID: 2960 Comm: rtcwake Not tainted 6.6.0-rc6-00002-g3e2c7f3ac51f #1025 Call Trace: <TASK> dump_stack_lvl+0x44/0x60 check_preemption_disabled+0xce/0xf0 ? __pfx_x86_pmu_dead_cpu+0x10/0x10 amd_pmu_lbr_reset+0x19/0xc0 ? __pfx_x86_pmu_dead_cpu+0x10/0x10 amd_pmu_cpu_reset.constprop.0+0x51/0x60 amd_pmu_cpu_dead+0x3e/0x90 x86_pmu_dead_cpu+0x13/0x20 cpuhp_invoke_callback+0x169/0x4b0 ? __pfx_virtnet_cpu_dead+0x10/0x10 __cpuhp_invoke_callback_range+0x76/0xe0 _cpu_down+0x112/0x270 freeze_secondary_cpus+0x8e/0x280 suspend_devices_and_enter+0x342/0x900 pm_suspend+0x2fd/0x690 state_store+0x71/0xd0 kernfs_fop_write_iter+0x128/0x1c0 vfs_write+0x2db/0x400 ksys_write+0x5f/0xe0 do_syscall_64+0x59/0x90 ? srso_alias_return_thunk+0x5/0x7f ? count_memcg_events.constprop.0+0x1a/0x30 ? srso_alias_return_thunk+0x5/0x7f ? handle_mm_fault+0x1e9/0x340 ? srso_alias_return_thunk+0x5/0x7f ? preempt_count_add+0x4d/0xa0 ? srso_alias_return_thunk+0x5/0x7f ? up_read+0x38/0x70 ? srso_alias_return_thunk+0x5/0x7f ? do_user_addr_fault+0x343/0x6b0 ? srso_alias_return_thunk+0x5/0x7f ? exc_page_fault+0x74/0x170 entry_SYSCALL_64_after_hwframe+0x6e/0xd8 RIP: 0033:0x7f32f8d14a77 Code: 10 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24 RSP: 002b:00007ffdc648de18 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007f32f8d14a77 RDX: 0000000000000004 RSI: 000055b2fc2a5670 RDI: 0000000000000004 RBP: 000055b2fc2a5670 R08: 0000000000000000 R09: 000055b2fc2a5670 R10: 00007f32f8e1a2f0 R11: 0000000000000246 R12: 0000000000000004 R13: 000055b2fc2a2480 R14: 00007f32f8e16600 R15: 00007f32f8e15a00 </TASK>
>> >> Call Trace: >> <TASK> >> dump_stack_lvl+0x44/0x60 >> check_preemption_disabled+0xce/0xf0 >> ? __pfx_x86_pmu_dead_cpu+0x10/0x10 >> amd_pmu_lbr_reset+0x19/0xc0 >> ? __pfx_x86_pmu_dead_cpu+0x10/0x10 >> amd_pmu_cpu_reset.constprop.0+0x51/0x60 >> amd_pmu_cpu_dead+0x3e/0x90 >> x86_pmu_dead_cpu+0x13/0x20 >> cpuhp_invoke_callback+0x169/0x4b0 >> ? __pfx_virtnet_cpu_dead+0x10/0x10 >> __cpuhp_invoke_callback_range+0x76/0xe0 >> _cpu_down+0x112/0x270 >> freeze_secondary_cpus+0x8e/0x280 >> suspend_devices_and_enter+0x342/0x900 >> pm_suspend+0x2fd/0x690 >> state_store+0x71/0xd0 >> kernfs_fop_write_iter+0x128/0x1c0 >> vfs_write+0x2db/0x400 >> ksys_write+0x5f/0xe0 >> do_syscall_64+0x59/0x90 >>
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