Messages in this thread | | | Date | Tue, 24 Oct 2023 10:02:13 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 2/2] perf/x86/amd: Don't allow pre-emption in amd_pmu_lbr_reset() |
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* 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
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