lkml.org 
[lkml]   [2023]   [Oct]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH 2/2] perf/x86/amd: Don't allow pre-emption in amd_pmu_lbr_reset()
From
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.

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

\
 
 \ /
  Last update: 2023-10-24 17:33    [W:1.000 / U:0.340 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site