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SubjectRe: [PATCH] irqchip/gic-v4.1: Use GFP_ATOMIC flag in allocate_vpe_l1_table()
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Hi Marc,

On 2020/6/30 21:37, Zenghui Yu wrote:
> Booting the latest kernel with DEBUG_ATOMIC_SLEEP=y on a GICv4.1 enabled
> box, I get the following kernel splat:
>
> [ 0.053766] BUG: sleeping function called from invalid context at mm/slab.h:567
> [ 0.053767] in_atomic(): 1, irqs_disabled(): 128, non_block: 0, pid: 0, name: swapper/1
> [ 0.053769] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.8.0-rc3+ #23
> [ 0.053770] Call trace:
> [ 0.053774] dump_backtrace+0x0/0x218
> [ 0.053775] show_stack+0x2c/0x38
> [ 0.053777] dump_stack+0xc4/0x10c
> [ 0.053779] ___might_sleep+0xfc/0x140
> [ 0.053780] __might_sleep+0x58/0x90
> [ 0.053782] slab_pre_alloc_hook+0x7c/0x90
> [ 0.053783] kmem_cache_alloc_trace+0x60/0x2f0
> [ 0.053785] its_cpu_init+0x6f4/0xe40
> [ 0.053786] gic_starting_cpu+0x24/0x38
> [ 0.053788] cpuhp_invoke_callback+0xa0/0x710
> [ 0.053789] notify_cpu_starting+0xcc/0xd8
> [ 0.053790] secondary_start_kernel+0x148/0x200
>
> # ./scripts/faddr2line vmlinux its_cpu_init+0x6f4/0xe40
> its_cpu_init+0x6f4/0xe40:
> allocate_vpe_l1_table at drivers/irqchip/irq-gic-v3-its.c:2818
> (inlined by) its_cpu_init_lpis at drivers/irqchip/irq-gic-v3-its.c:3138
> (inlined by) its_cpu_init at drivers/irqchip/irq-gic-v3-its.c:5166
>
> It turned out that we're allocating memory using GFP_KERNEL (may sleep)
> within the CPU hotplug notifier, which is indeed an atomic context. Bad
> thing may happen if we're playing on a system with more than a single
> CommonLPIAff group. Avoid it by turning this into an atomic allocation.
>
> Fixes: 5e5168461c22 ("irqchip/gic-v4.1: VPE table (aka GICR_VPROPBASER) allocation")
> Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
> ---
> drivers/irqchip/irq-gic-v3-its.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 6a5a87fc4601..b66eeca442c4 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -2814,7 +2814,7 @@ static int allocate_vpe_l1_table(void)
> if (val & GICR_VPROPBASER_4_1_VALID)
> goto out;
>
> - gic_data_rdist()->vpe_table_mask = kzalloc(sizeof(cpumask_t), GFP_KERNEL);
> + gic_data_rdist()->vpe_table_mask = kzalloc(sizeof(cpumask_t), GFP_ATOMIC);
> if (!gic_data_rdist()->vpe_table_mask)
> return -ENOMEM;
>
> @@ -2881,7 +2881,7 @@ static int allocate_vpe_l1_table(void)
>
> pr_debug("np = %d, npg = %lld, psz = %d, epp = %d, esz = %d\n",
> np, npg, psz, epp, esz);
> - page = alloc_pages(GFP_KERNEL | __GFP_ZERO, get_order(np * PAGE_SIZE));
> + page = alloc_pages(GFP_ATOMIC | __GFP_ZERO, get_order(np * PAGE_SIZE));
> if (!page)
> return -ENOMEM;
>

Do you mind taking this patch into v5.9? Or please let me know if you
still have any concerns on it?


Thanks,
Zenghui

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