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SubjectRe: [PATCH] HID: usbhid: Use GFP_KERNEL instead of GFP_ATOMIC when applicable
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Hi, (and sorry if you receive this email twice. I've used a web mail 
which sends HTML by default and it was rejected by ML)

Le 01/08/2019 à 12:06, walter harms a écrit :
>
>
> Am 01.08.2019 09:47, schrieb Christophe JAILLET:
>> There is no need to use GFP_ATOMIC when calling 'usb_alloc_coherent()'
>> here. These calls are done from probe functions and using GFP_KERNEL should
>> be safe.
>> The memory itself is used within some interrupts, but it is not a
>> problem, once it has been allocated.
>>
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
>> ---
>> drivers/hid/usbhid/usbkbd.c | 4 ++--
>> drivers/hid/usbhid/usbmouse.c | 2 +-
>> 2 files changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/hid/usbhid/usbkbd.c b/drivers/hid/usbhid/usbkbd.c
>> index d5b7a696a68c..63e8ef8beb45 100644
>> --- a/drivers/hid/usbhid/usbkbd.c
>> +++ b/drivers/hid/usbhid/usbkbd.c
>> @@ -239,11 +239,11 @@ static int usb_kbd_alloc_mem(struct usb_device *dev, struct usb_kbd *kbd)
>> return -1;
>> if (!(kbd->led = usb_alloc_urb(0, GFP_KERNEL)))
>> return -1;
>> - if (!(kbd->new = usb_alloc_coherent(dev, 8, GFP_ATOMIC, &kbd->new_dma)))
>> + if (!(kbd->new = usb_alloc_coherent(dev, 8, GFP_KERNEL, &kbd->new_dma)))
>> return -1;
>> if (!(kbd->cr = kmalloc(sizeof(struct usb_ctrlrequest), GFP_KERNEL)))
>> return -1;
>> - if (!(kbd->leds = usb_alloc_coherent(dev, 1, GFP_ATOMIC, &kbd->leds_dma)))
>> + if (!(kbd->leds = usb_alloc_coherent(dev, 1, GFP_KERNEL, &kbd->leds_dma)))
>> return -1;
>>
>
> the kernel style is usually:
> kbd->new = usb_alloc_coherent(dev, 8, GFP_ATOMIC, &kbd->new_dma);
> if (!kbd->new)
> return -1;
>

Searching with coccinelle with:
* x = usb_alloc_coherent(..., <+... GFP_KERNEL ...+>, ...);
finds 67 files,

whereas:
* x = usb_alloc_coherent(..., <+... GFP_ATOMIC ...+>, ...);
only finds 11 files.

>
> in usbmouse.c this is done, any reason for the change here ?
>

No real reason in fact, just to be consistent with surrounding code.

Unless some allocations are done within a spin_lock/spin_unlock, using
both GFP_KERNEL and GFP_ATOMIC in the same function looks spurious to me.
Either there is a bug (GFP_KERNEL should be GFP_ATOMIC), or a useless
constraint is given to the memory allocator.

CJ

> re,
> wh
>
>> return 0;
>> diff --git a/drivers/hid/usbhid/usbmouse.c b/drivers/hid/usbhid/usbmouse.c
>> index 073127e65ac1..c89332017d5d 100644
>> --- a/drivers/hid/usbhid/usbmouse.c
>> +++ b/drivers/hid/usbhid/usbmouse.c
>> @@ -130,7 +130,7 @@ static int usb_mouse_probe(struct usb_interface *intf, const struct usb_device_i
>> if (!mouse || !input_dev)
>> goto fail1;
>>
>> - mouse->data = usb_alloc_coherent(dev, 8, GFP_ATOMIC, &mouse->data_dma);
>> + mouse->data = usb_alloc_coherent(dev, 8, GFP_KERNEL, &mouse->data_dma);
>> if (!mouse->data)
>> goto fail1;
>>
>

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