netdev - Re: [PATCH -next] um: vector: use GFP_ATOMIC under spin lock

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Date:   Thu, 28 Nov 2019 09:22:59 +0000
From:   Anton Ivanov <anton.ivanov@...bridgegreys.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Song Liu <songliubraving@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Richard Weinberger <richard@....at>,
        Jeff Dike <jdike@...toit.com>, kernel-janitors@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        linux-um@...ts.infradead.org, Wei Yongjun <weiyongjun1@...wei.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        Martin KaFai Lau <kafai@...com>
Subject: Re: [PATCH -next] um: vector: use GFP_ATOMIC under spin lock

On 28/11/2019 08:37, Dan Carpenter wrote:
> On Thu, Nov 28, 2019 at 08:18:30AM +0000, Anton Ivanov wrote:
>>
>>
>> On 28/11/2019 08:06, Dan Carpenter wrote:
>>> On Thu, Nov 28, 2019 at 02:01:47AM +0000, Wei Yongjun wrote:
>>>> A spin lock is taken here so we should use GFP_ATOMIC.
>>>>
>>>> Fixes: 9807019a62dc ("um: Loadable BPF "Firmware" for vector drivers")
>>>> Signed-off-by: Wei Yongjun <weiyongjun1@...wei.com>
>>>> ---
>>>>    arch/um/drivers/vector_kern.c | 4 ++--
>>>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/arch/um/drivers/vector_kern.c b/arch/um/drivers/vector_kern.c
>>>> index 92617e16829e..6ff0065a271d 100644
>>>> --- a/arch/um/drivers/vector_kern.c
>>>> +++ b/arch/um/drivers/vector_kern.c
>>>> @@ -1402,7 +1402,7 @@ static int vector_net_load_bpf_flash(struct net_device *dev,
>>>>    		kfree(vp->bpf->filter);
>>>>    		vp->bpf->filter = NULL;
>>>>    	} else {
>>>> -		vp->bpf = kmalloc(sizeof(struct sock_fprog), GFP_KERNEL);
>>>> +		vp->bpf = kmalloc(sizeof(struct sock_fprog), GFP_ATOMIC);
>>>>    		if (vp->bpf == NULL) {
>>>>    			netdev_err(dev, "failed to allocate memory for firmware\n");
>>>>    			goto flash_fail;
>>>> @@ -1414,7 +1414,7 @@ static int vector_net_load_bpf_flash(struct net_device *dev,
>>>>    	if (request_firmware(&fw, efl->data, &vdevice->pdev.dev))
>>>               ^^^^^^^^^^^^^^^^
>>>
>>> Is it really possible to call request_firmware() while holding a
>>> spin_lock?  I was so sure that read from the disk.
>>
>> Works, I tested the patch quite a few times.
>>
> 
> Do you have CONFIG_DEBUG_ATOMIC_SLEEP enabled?  The GFP_KERNEL calls
> should have triggered a warning if so.

I do not think we can use that in um.

config DEBUG_ATOMIC_SLEEP
         bool "Sleep inside atomic section checking"
         select PREEMPT_COUNT
         depends on DEBUG_KERNEL
         depends on !ARCH_NO_PREEMPT

In arch/um/Kconfig

         select ARCH_NO_PREEMPT

Brgds,

> 
> regards,
> dan carpenter
> 
> 
> _______________________________________________
> linux-um mailing list
> linux-um@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-um
> 

-- 
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/

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