Re: [PATCH] HID: usbhid: Use GFP_KERNEL instead of GFP_ATOMIC when applicable

[Christophe JAILLET]

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.jail...@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;