In KvmTool, on a ThunderX2, when running a preemp_rt kernel based on
v5.19-rc3-rt4, the following happens:
[ 4.070739] [ BUG: Invalid wait context ]
[ 4.070740] 5.19.0-rc3-rt4-00001-g1a6597c0bdcf #153 Not tainted
[ 4.070742] -----------------------------
[ 4.070743] swapper/0/1 is trying to lock:
[ 4.070744] ffff0000ab7405d8 ((&c->lock)){+.+.}-{3:3}, at: ___slab_alloc (mm/slub.c:2954)
[ 4.070757] other info that might help us debug this:
[ 4.070758] context-{5:5}
[ 4.070759] 5 locks held by swapper/0/1:
[ 4.070760] #0: ffff0000811491e0 (&dev->mutex){....}-{4:4}, at: __device_driver_lock (drivers/base/dd.c:1055)
[ 4.070769] #1: ffff0000846c5670 (&desc->request_mutex){+.+.}-{4:4}, at: __setup_irq (kernel/irq/internals.h:147)
[ 4.070778] #2: ffff0000846c54c8 (&irq_desc_lock_class){....}-{2:2}, at: __setup_irq (kernel/irq/manage.c:1612)
[ 4.070784] #3: ffff80000b23ea78 (mask_lock){....}-{2:2}, at: irq_setup_affinity (./include/linux/irq.h:381)
[ 4.070791] #4: ffff80000b23ea38 (tmp_mask_lock){....}-{2:2}, at: irq_do_set_affinity (./include/linux/irq.h:381)
[ 4.070797] stack backtrace:
[ 4.070801] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 5.19.0-rc3-rt4-00001-g1a6597c0bdcf #153
[ 4.070805] Call trace:
[ 4.070806] dump_backtrace (arch/arm64/kernel/stacktrace.c:200)
[ 4.070811] show_stack (arch/arm64/kernel/stacktrace.c:207)
[ 4.070813] dump_stack_lvl (lib/dump_stack.c:107)
[ 4.070818] dump_stack (lib/dump_stack.c:114)
[ 4.070820] __lock_acquire (kernel/locking/lockdep.c:4707)
[ 4.070823] lock_acquire (kernel/locking/lockdep.c:466)
[ 4.070825] rt_spin_lock (./arch/arm64/include/asm/current.h:19 (discriminator 4))
[ 4.070830] ___slab_alloc (mm/slub.c:2954)
[ 4.070832] __slab_alloc.isra.0 (mm/slub.c:3116)
[ 4.070835] __kmalloc_node (mm/slub.c:3207)
[ 4.070837] alloc_cpumask_var_node (lib/cpumask.c:115)
[ 4.070843] alloc_cpumask_var (lib/cpumask.c:147)
[ 4.070846] its_select_cpu (drivers/irqchip/irq-gic-v3-its.c:1580)
[ 4.070850] its_set_affinity (drivers/irqchip/irq-gic-v3-its.c:1659)
[ 4.070853] msi_domain_set_affinity (kernel/irq/msi.c:501)
[ 4.070857] irq_do_set_affinity (kernel/irq/manage.c:276)
[ 4.070860] irq_setup_affinity (kernel/irq/manage.c:633)
[ 4.070863] irq_startup (kernel/irq/chip.c:280)
[ 4.070865] __setup_irq (kernel/irq/manage.c:1777)
[ 4.070869] request_threaded_irq (kernel/irq/manage.c:2206)
[ 4.070872] vp_find_vqs_msix (./include/linux/interrupt.h:168)
[ 4.070876] vp_find_vqs (drivers/virtio/virtio_pci_common.c:400)
[ 4.070878] vp_modern_find_vqs (drivers/virtio/virtio_pci_modern.c:259)
[ 4.070880] init_vq (./include/linux/virtio_config.h:213)
[ 4.070885] virtblk_probe (drivers/block/virtio_blk.c:936)
[ 4.070887] virtio_dev_probe (drivers/virtio/virtio.c:303)
[ 4.070892] really_probe (drivers/base/dd.c:555)
[ 4.070895] __driver_probe_device (drivers/base/dd.c:764)
[ 4.070897] driver_probe_device (drivers/base/dd.c:794)
[ 4.070899] __driver_attach (drivers/base/dd.c:1164)
[ 4.070901] bus_for_each_dev (drivers/base/bus.c:301)
[ 4.070904] driver_attach (drivers/base/dd.c:1181)
[ 4.070906] bus_add_driver (drivers/base/bus.c:618)
[ 4.070908] driver_register (drivers/base/driver.c:240)
[ 4.070910] register_virtio_driver (drivers/virtio/virtio.c:356 (discriminator 4))
[ 4.070913] virtio_blk_init (drivers/block/virtio_blk.c:1218)
[ 4.070918] do_one_initcall (init/main.c:1295)
[ 4.070921] kernel_init_freeable (init/main.c:1367)
[ 4.070924] kernel_init (init/main.c:1503)
[ 4.070927] ret_from_fork (arch/arm64/kernel/entry.S:868)
commit cba4235e6031e ("genirq: Remove mask argument from
setup_affinity()")
and
commit 11ea68f553e24 ("genirq, sched/isolation: Isolate from handling
managed interrupts")
overcome this issue by defining a static struct cpumask and protecting
it by a raw spinlock. The code in these commits is executed with IRQs
disabled.
its_select_cpu() can be executed with IRQs enabled or disabled. Thus
disabling IRQs is necesserary to avoid deadlocking.
This patch:
- makes tmpmask a 'static struct cpumask'. This prevents storing it on
the stack and having to dynamically allocate it
- protects tmpmask with a raw spinlock
- disables IRQs around the spinlock for the case its_select_cpu() is
called with IRQs enabled
Signed-off-by: Pierre Gondois <pierre.gondois@xxxxxxx>
---
drivers/irqchip/irq-gic-v3-its.c | 34 +++++++++++++++++---------------
1 file changed, 18 insertions(+), 16 deletions(-)
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 5ff09de6c48f..3cf89e59b036 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -1574,14 +1574,15 @@ static int its_select_cpu(struct irq_data *d,
const struct cpumask *aff_mask)
{
struct its_device *its_dev = irq_data_get_irq_chip_data(d);
- cpumask_var_t tmpmask;
+ static DEFINE_RAW_SPINLOCK(tmpmask_lock);
+ static struct cpumask tmpmask;
+ unsigned long flags;
int cpu, node;
-
- if (!alloc_cpumask_var(&tmpmask, GFP_ATOMIC))
- return -ENOMEM;
-
node = its_dev->its->numa_node;
+ local_irq_save(flags);
+ raw_spin_lock(&tmpmask_lock);
+
if (!irqd_affinity_is_managed(d)) {
/* First try the NUMA node */
if (node != NUMA_NO_NODE) {
@@ -1589,8 +1590,8 @@ static int its_select_cpu(struct irq_data *d,
* Try the intersection of the affinity mask and the
* node mask (and the online mask, just to be safe).
*/
- cpumask_and(tmpmask, cpumask_of_node(node), aff_mask);
- cpumask_and(tmpmask, tmpmask, cpu_online_mask);
+ cpumask_and(&tmpmask, cpumask_of_node(node), aff_mask);
+ cpumask_and(&tmpmask, &tmpmask, cpu_online_mask);
/*
* Ideally, we would check if the mask is empty, and
@@ -1604,7 +1605,7 @@ static int its_select_cpu(struct irq_data *d,
* Instead, just fallback on the online mask. This
* diverges from Thomas' suggestion above.
*/
- cpu = cpumask_pick_least_loaded(d, tmpmask);
+ cpu = cpumask_pick_least_loaded(d, &tmpmask);
if (cpu < nr_cpu_ids)
goto out;
@@ -1616,25 +1617,26 @@ static int its_select_cpu(struct irq_data *d,
}
/* Try the intersection of the affinity and online masks */
- cpumask_and(tmpmask, aff_mask, cpu_online_mask);
+ cpumask_and(&tmpmask, aff_mask, cpu_online_mask);
/* If that doesn't fly, the online mask is the last resort */
- if (cpumask_empty(tmpmask))
- cpumask_copy(tmpmask, cpu_online_mask);
+ if (cpumask_empty(&tmpmask))
+ cpumask_copy(&tmpmask, cpu_online_mask);
- cpu = cpumask_pick_least_loaded(d, tmpmask);
+ cpu = cpumask_pick_least_loaded(d, &tmpmask);
} else {
- cpumask_copy(tmpmask, aff_mask);
+ cpumask_copy(&tmpmask, aff_mask);
/* If we cannot cross sockets, limit the search to that node */
if ((its_dev->its->flags & ITS_FLAGS_WORKAROUND_CAVIUM_23144) &&
node != NUMA_NO_NODE)
- cpumask_and(tmpmask, tmpmask, cpumask_of_node(node));
+ cpumask_and(&tmpmask, &tmpmask, cpumask_of_node(node));
- cpu = cpumask_pick_least_loaded(d, tmpmask);
+ cpu = cpumask_pick_least_loaded(d, &tmpmask);
}
out:
- free_cpumask_var(tmpmask);
+ raw_spin_unlock(&tmpmask_lock);
+ local_irq_restore(flags);
pr_debug("IRQ%d -> %*pbl CPU%d\n", d->irq, cpumask_pr_args(aff_mask), cpu);
return cpu;
--
2.25.1
