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Date:   Mon, 27 Jul 2020 08:57:58 +0100
From:   Marc Zyngier <maz@kernel.org>
To:     Zenghui Yu <yuzenghui@huawei.com>
Cc:     linux-kernel@vger.kernel.org, tglx@linutronix.de,
        jason@lakedaemon.net, wanghaibin.wang@huawei.com,
        kuhn.chenqun@huawei.com, wangjingyi11@huawei.com
Subject: Re: [PATCH] irqchip/gic-v4.1: Use GFP_ATOMIC flag in
 allocate_vpe_l1_table()
In-Reply-To: <076a3e82-ba21-6e6a-c6cd-937abb063eb9@huawei.com>
References: <20200630133746.816-1-yuzenghui@huawei.com>
 <076a3e82-ba21-6e6a-c6cd-937abb063eb9@huawei.com>
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Hi Zenghui,

On 2020-07-27 04:50, Zenghui Yu wrote:
> 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?

Oops, I seem to have dropped this one on the floor.
I've picked it up now.

Thanks for the heads up,

         M.
-- 
Jazz is not dead. It just smells funny...