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Message-ID: <47518940-2803-4a6b-88fd-8cfc872b4219@amd.com>
Date: Tue, 24 Oct 2023 11:04:06 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
Thomas Gleixner <tglx@...utronix.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Sandipan Das <sandipan.das@....com>,
"H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
x86@...nel.org, linux-pm@...r.kernel.org, rafael@...nel.org,
pavel@....cz, linux-perf-users@...r.kernel.org,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH 2/2] perf/x86/amd: Don't allow pre-emption in
amd_pmu_lbr_reset()
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@....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@...r.kernel.org # 6.1+
>>>> Fixes: ca5b7c0d9621 ("perf/x86/amd/lbr: Add LbrExtV2 branch record support")
>>>> Signed-off-by: Mario Limonciello <mario.limonciello@....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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