----- Ursprüngliche Mail -----
> Von: "anton ivanov" <anton.ivanov@xxxxxxxxxxxxxxxxxx>
> An: "Dan Carpenter" <dan.carpenter@xxxxxxxxxx>, "Wei Yongjun" <weiyongjun1@xxxxxxxxxx>
> CC: "Song Liu" <songliubraving@xxxxxx>, "Daniel Borkmann" <daniel@xxxxxxxxxxxxx>, "kernel-janitors"
> <kernel-janitors@xxxxxxxxxxxxxxx>, "richard" <richard@xxxxxx>, "Jeff Dike" <jdike@xxxxxxxxxxx>, "linux-um"
> <linux-um@xxxxxxxxxxxxxxxxxxx>, "Alexei Starovoitov" <ast@xxxxxxxxxx>, "netdev" <netdev@xxxxxxxxxxxxxxx>,
> bpf@xxxxxxxxxxxxxxx, "Martin KaFai Lau" <kafai@xxxxxx>
> Gesendet: Donnerstag, 28. November 2019 09:18:30
> Betreff: Re: [PATCH -next] um: vector: use GFP_ATOMIC under spin lock
> 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@xxxxxxxxxx>
>>> ---
>>> 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.
It works because of the nature of UML ->no SMP or PREEMPT.
But better request the firmware before taking the spinlock.
request_firmware() can block.
Same for the kmalloc(), just allocate the buffer before and then assign
the pointer under the lock. That way you don't need GFP_ATOMIC.
Thanks,
//richard
