From 727653d6ce7103b245eb8041f55dd5885f4c3289 Mon Sep 17 00:00:00 2001 From: James Morse Date: Mon, 19 Sep 2016 18:29:15 +0100 Subject: [PATCH] irqchip/gicv3: Silence noisy DEBUG_PER_CPU_MAPS warning gic_raise_softirq() walks the list of cpus using for_each_cpu(), it calls gic_compute_target_list() which advances the iterator by the number of CPUs in the cluster. If gic_compute_target_list() reaches the last CPU it leaves the iterator pointing at the last CPU. This means the next time round the for_each_cpu() loop cpumask_next() will be called with an invalid CPU. This triggers a warning when built with CONFIG_DEBUG_PER_CPU_MAPS: [ 3.077738] GICv3: CPU1: found redistributor 1 region 0:0x000000002f120000 [ 3.077943] CPU1: Booted secondary processor [410fd0f0] [ 3.078542] ------------[ cut here ]------------ [ 3.078746] WARNING: CPU: 1 PID: 0 at ../include/linux/cpumask.h:121 gic_raise_softirq+0x12c/0x170 [ 3.078812] Modules linked in: [ 3.078869] [ 3.078930] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.8.0-rc5+ #5188 [ 3.078994] Hardware name: Foundation-v8A (DT) [ 3.079059] task: ffff80087a1a0080 task.stack: ffff80087a19c000 [ 3.079145] PC is at gic_raise_softirq+0x12c/0x170 [ 3.079226] LR is at gic_raise_softirq+0xa4/0x170 [ 3.079296] pc : [] lr : [] pstate: 200001c9 [ 3.081139] Call trace: [ 3.081202] Exception stack(0xffff80087a19fbe0 to 0xffff80087a19fd10) [ 3.082269] [] gic_raise_softirq+0x12c/0x170 [ 3.082354] [] smp_send_reschedule+0x34/0x40 [ 3.082433] [] resched_curr+0x50/0x88 [ 3.082512] [] check_preempt_curr+0x60/0xd0 [ 3.082593] [] ttwu_do_wakeup+0x20/0xe8 [ 3.082672] [] ttwu_do_activate+0x90/0xc0 [ 3.082753] [] try_to_wake_up+0x224/0x370 [ 3.082836] [] default_wake_function+0x10/0x18 [ 3.082920] [] __wake_up_common+0x5c/0xa0 [ 3.083003] [] __wake_up_locked+0x14/0x20 [ 3.083086] [] complete+0x40/0x60 [ 3.083168] [] secondary_start_kernel+0x15c/0x1d0 [ 3.083240] [<00000000808911a4>] 0x808911a4 [ 3.113401] Detected PIPT I-cache on CPU2 Avoid updating the iterator if the next call to cpumask_next() would cause the for_each_cpu() loop to exit. There is no change to gic_raise_softirq()'s behaviour, (cpumask_next()s eventual call to _find_next_bit() will return early as start >= nbits), this patch just silences the warning. Fixes: 021f653791ad ("irqchip: gic-v3: Initial support for GICv3") Signed-off-by: James Morse Acked-by: Marc Zyngier Cc: linux-arm-kernel@lists.infradead.org Cc: Jason Cooper Link: http://lkml.kernel.org/r/1474306155-3303-1-git-send-email-james.morse@arm.com Signed-off-by: Thomas Gleixner --- drivers/irqchip/irq-gic-v3.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c index ede5672ab34d..da6c0ba61d4f 100644 --- a/drivers/irqchip/irq-gic-v3.c +++ b/drivers/irqchip/irq-gic-v3.c @@ -548,7 +548,7 @@ static int gic_starting_cpu(unsigned int cpu) static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask, unsigned long cluster_id) { - int cpu = *base_cpu; + int next_cpu, cpu = *base_cpu; unsigned long mpidr = cpu_logical_map(cpu); u16 tlist = 0; @@ -562,9 +562,10 @@ static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask, tlist |= 1 << (mpidr & 0xf); - cpu = cpumask_next(cpu, mask); - if (cpu >= nr_cpu_ids) + next_cpu = cpumask_next(cpu, mask); + if (next_cpu >= nr_cpu_ids) goto out; + cpu = next_cpu; mpidr = cpu_logical_map(cpu);