linux-kernel - Re: [PATCH] irqchip/gic-v4.1: Use GFP_ATOMIC flag in allocate_vpe_l1

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Date:   Mon, 27 Jul 2020 11:50:36 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     <linux-kernel@...r.kernel.org>, <maz@...nel.org>
CC:     <tglx@...utronix.de>, <jason@...edaemon.net>,
        <wanghaibin.wang@...wei.com>, <kuhn.chenqun@...wei.com>,
        <wangjingyi11@...wei.com>
Subject: Re: [PATCH] irqchip/gic-v4.1: Use GFP_ATOMIC flag in
 allocate_vpe_l1_table()

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@...wei.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