[PATCH] bus: arm-ccn: Handle correctly no-more-cpus case
From: mark.rutland@arm.com (Mark Rutland)
Date: 2015-05-14 11:04:28
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kernel-janitors
On Thu, May 14, 2015 at 11:50:24AM +0100, Pawel Moll wrote:
When migrating events the driver picks another cpu using cpumask_any_but() function, which returns value >= nr_cpu_ids when there is none available, not a negative value as the code assumed. Fixed now.
The fix looks good to me: Acked-by: Mark Rutland <mark.rutland@arm.com> Does this need to be CC'd to stable? What does perf_pmu_migrate_context do when passed a target >= nr_cpus? The original bug seems to have been copied over from arm-cci.c, which will need the same fix. That appears to be my fault -- I'd mostly been following the x86 uncore PMU drivers, but they figure out the target CPU in a different way for which -1 is a sane error case. I'll spin a patch for arm-cci.c momentarily. Thanks, Mark.
quoted hunk ↗ jump to hunk
Reported-by: Dan Carpenter <redacted> Signed-off-by: Pawel Moll <redacted> --- Another day, another arm-ccn.c update... This time Dan's static checker spotted unsigned int target being expected to carry negative values. Fixed now. Interestingly enough, cpumask_any_but() implementation (and its normal prototype) returns int, but version for NR_CPUS == 1 case, inlined in linux/cpumask.h returns unsigned int... drivers/bus/arm-ccn.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/drivers/bus/arm-ccn.c b/drivers/bus/arm-ccn.c index 7d9879e..cc322fb 100644 --- a/drivers/bus/arm-ccn.c +++ b/drivers/bus/arm-ccn.c@@ -1184,7 +1184,7 @@ static int arm_ccn_pmu_cpu_notifier(struct notifier_block *nb, if (!cpumask_test_and_clear_cpu(cpu, &dt->cpu)) break; target = cpumask_any_but(cpu_online_mask, cpu); - if (target < 0) + if (target >= nr_cpu_ids) break; perf_pmu_migrate_context(&dt->pmu, cpu, target); cpumask_set_cpu(target, &dt->cpu);-- 2.1.0