Messages in this thread | | | Date | Tue, 24 Oct 2023 10:32:27 -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 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
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