4.9-stable review patch. If anyone has any objections, please let me know.
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From: Marc Zyngier marc.zyngier@arm.com
commit b18c2b9487d8e797fc0a757e57ac3645348c5fba upstream.
Booting a DEBUG_PREEMPT enabled kernel on a CCN-based system results in the following splat:
[...] arm-ccn e8000000.ccn: No access to interrupts, using timer. BUG: using smp_processor_id() in preemptible [00000000] code: swapper/0/1 caller is debug_smp_processor_id+0x1c/0x28 CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.13.0 #6111 Hardware name: AMD Seattle/Seattle, BIOS 17:08:23 Jun 26 2017 Call trace: [<ffff000008089e78>] dump_backtrace+0x0/0x278 [<ffff00000808a22c>] show_stack+0x24/0x30 [<ffff000008bc3bc4>] dump_stack+0x8c/0xb0 [<ffff00000852b534>] check_preemption_disabled+0xfc/0x100 [<ffff00000852b554>] debug_smp_processor_id+0x1c/0x28 [<ffff000008551bd8>] arm_ccn_probe+0x358/0x4f0 [...]
as we use smp_processor_id() in the wrong context.
Turn this into a get_cpu()/put_cpu() that extends over the CPU hotplug registration, making sure that we don't race against a CPU down operation.
Signed-off-by: Marc Zyngier marc.zyngier@arm.com Acked-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Pawel Moll pawel.moll@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/bus/arm-ccn.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/drivers/bus/arm-ccn.c +++ b/drivers/bus/arm-ccn.c @@ -1301,7 +1301,7 @@ static int arm_ccn_pmu_init(struct arm_c }
/* Pick one CPU which we will use to collect data from CCN... */ - cpumask_set_cpu(smp_processor_id(), &ccn->dt.cpu); + cpumask_set_cpu(get_cpu(), &ccn->dt.cpu);
/* Also make sure that the overflow interrupt is handled by this CPU */ if (ccn->irq) { @@ -1318,10 +1318,12 @@ static int arm_ccn_pmu_init(struct arm_c
cpuhp_state_add_instance_nocalls(CPUHP_AP_PERF_ARM_CCN_ONLINE, &ccn->dt.node); + put_cpu(); return 0;
error_pmu_register: error_set_affinity: + put_cpu(); error_choose_name: ida_simple_remove(&arm_ccn_pmu_ida, ccn->dt.id); for (i = 0; i < ccn->num_xps; i++)