| Message ID | 20210518093118.505110632@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | genirq, perf: Cleanup the abuse of irq_set_affinity_hint() | expand |
On 18/05/2021 10:17, Thomas Gleixner wrote: > > @@ -769,7 +769,6 @@ static int dsu_pmu_device_probe(struct p > if (rc) { nit: I think that someone will send a patch to remove these {} later... > cpuhp_state_remove_instance(dsu_pmu_cpuhp_state, > &dsu_pmu->cpuhp_node); > - irq_set_affinity_hint(dsu_pmu->irq, NULL); > } Thanks, John
On Tue, May 18 2021 at 12:31, John Garry wrote: > On 18/05/2021 10:17, Thomas Gleixner wrote: >> >> @@ -769,7 +769,6 @@ static int dsu_pmu_device_probe(struct p >> if (rc) { > > nit: I think that someone will send a patch to remove these {} later... > >> cpuhp_state_remove_instance(dsu_pmu_cpuhp_state, >> &dsu_pmu->cpuhp_node); >> - irq_set_affinity_hint(dsu_pmu->irq, NULL); >> } which should be rejected because cpuhp_state_remove_instance(dsu_pmu_cpuhp_state, &dsu_pmu->cpuhp_node); is _NOT_ a one line statement. if (foo) cpuhp_state_remove_instance(state, &node); is fine, but if (foo) cpuhp_state_remove_instance(dsu_pmu_cpuhp_state, &dsu_pmu->cpuhp_node); breaks the expectation of a single line following the condition which confuses my brain based OCR. :) So I left the brackets there on purpose. Thanks, tglx
--- a/drivers/perf/arm_dsu_pmu.c +++ b/drivers/perf/arm_dsu_pmu.c @@ -687,7 +687,7 @@ static void dsu_pmu_probe_pmu(struct dsu static void dsu_pmu_set_active_cpu(int cpu, struct dsu_pmu *dsu_pmu) { cpumask_set_cpu(cpu, &dsu_pmu->active_cpu); - if (irq_set_affinity_hint(dsu_pmu->irq, &dsu_pmu->active_cpu)) + if (irq_set_affinity(dsu_pmu->irq, &dsu_pmu->active_cpu)) pr_warn("Failed to set irq affinity to %d\n", cpu); } @@ -769,7 +769,6 @@ static int dsu_pmu_device_probe(struct p if (rc) { cpuhp_state_remove_instance(dsu_pmu_cpuhp_state, &dsu_pmu->cpuhp_node); - irq_set_affinity_hint(dsu_pmu->irq, NULL); } return rc; @@ -781,7 +780,6 @@ static int dsu_pmu_device_remove(struct perf_pmu_unregister(&dsu_pmu->pmu); cpuhp_state_remove_instance(dsu_pmu_cpuhp_state, &dsu_pmu->cpuhp_node); - irq_set_affinity_hint(dsu_pmu->irq, NULL); return 0; } @@ -840,10 +838,8 @@ static int dsu_pmu_cpu_teardown(unsigned dst = dsu_pmu_get_online_cpu_any_but(dsu_pmu, cpu); /* If there are no active CPUs in the DSU, leave IRQ disabled */ - if (dst >= nr_cpu_ids) { - irq_set_affinity_hint(dsu_pmu->irq, NULL); + if (dst >= nr_cpu_ids) return 0; - } perf_pmu_migrate_context(&dsu_pmu->pmu, cpu, dst); dsu_pmu_set_active_cpu(dst, dsu_pmu);
The driver uses irq_set_affinity_hint() to set the affinity for the PMU interrupts, which relies on the undocumented side effect that this function actually sets the affinity under the hood. Setting an hint is clearly not a guarantee and for these PMU interrupts an affinity hint, which is supposed to guide userspace for setting affinity, is beyond pointless, because the affinity of these interrupts cannot be modified from user space. Aside of that the error checks are bogus because the only error which is returned from irq_set_affinity_hint() is when there is no irq descriptor for the interrupt number, but not when the affinity set fails. That's on purpose because the hint can point to an offline CPU. Replace the mindless abuse with irq_set_affinity(). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Will Deacon <will@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: linux-arm-kernel@lists.infradead.org --- drivers/perf/arm_dsu_pmu.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)