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arm64: topology: Fix false warning in counters_read_on_cpu() for same-CPU reads

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The counters_read_on_cpu() function warns when called with IRQs
disabled to prevent deadlock in smp_call_function_single(). However,
this warning is spurious when reading counters on the current CPU,
since no IPI is needed for same CPU reads.

Commit 12eb8f4fff24 ("cpufreq: CPPC: Update FIE arch_freq_scale in
ticks for non-PCC regs") changed the CPPC Frequency Invariance Engine
to read AMU counters directly from the scheduler tick for non-PCC
register spaces (like FFH), instead of deferring to a kthread. This
means counters_read_on_cpu() is now called with IRQs disabled from the
tick handler, triggering the warning.

Fix this by restructuring the logic: when IRQs are disabled (tick
context), call the function directly for same-CPU reads. Otherwise
use smp_call_function_single().

Fixes: 997c021abc ("cpufreq: CPPC: Update FIE arch_freq_scale in ticks for non-PCC regs")
Suggested-by: Will Deacon <will@kernel.org>
Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Sumit Gupta 2026-02-26 17:29:11 +05:30 • committed by Will Deacon
parent e5cb94ba5f
commit df6e4ab654
1 changed files with 15 additions and 6 deletions
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21
arch/arm64/kernel/topology.c
View file

@ -400,16 +400,25 @@ static inline
int counters_read_on_cpu(int cpu, smp_call_func_t func, u64 *val)
{
/*
* Abort call on counterless CPU or when interrupts are
* disabled - can lead to deadlock in smp sync call.
* Abort call on counterless CPU.
*/
if (!cpu_has_amu_feat(cpu))
return -EOPNOTSUPP;
if (WARN_ON_ONCE(irqs_disabled()))
return -EPERM;
smp_call_function_single(cpu, func, val, 1);
if (irqs_disabled()) {
/*
* When IRQs are disabled (tick path: sched_tick ->
* topology_scale_freq_tick or cppc_scale_freq_tick), only local
* CPU counter reads are allowed. Remote CPU counter read would
* require smp_call_function_single() which is unsafe with IRQs
* disabled.
*/
if (WARN_ON_ONCE(cpu != smp_processor_id()))
return -EPERM;
func(val);
} else {
smp_call_function_single(cpu, func, val, 1);
}
return 0;
}