usb_allocate_stream_buffers() is never called in atomic context.
The call chains ending up at usb_allocate_stream_buffers() are:
[1] usb_allocate_stream_buffers() <- usb_bulk_urb_init() <- usb_urb_init()
<- dvb_usb_adapter_stream_init() <- dvb_usb_adapter_init
<- dvb_usb_init() <- dvb_usb_device_init() <- xxx_probe()
[2] usb_allocate_stream_buffers() <- usb_isoc_urb_init() <- usb_urb_init()
<- dvb_usb_adapter_stream_init() <- dvb_usb_adapter_init
<- dvb_usb_init() <- dvb_usb_device_init() <- xxx_probe()
xxx_probe including ttusb2_probe, vp7045_usb_probe, a800_probe, and so on.
These xxx_probe() functions are set as ".probe" in struct usb_driver.
And these functions are not called in atomic context.
Despite never getting called from atomic context,
usb_allocate_stream_buffers() calls usb_alloc_coherent() with GFP_ATOMIC,
which does not sleep for allocation.
GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
which can sleep and improve the possibility of sucessful allocation.
This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.
Signed-off-by: Jia-Ju Bai <baijiaju1...@gmail.com>
---
drivers/media/usb/dvb-usb/usb-urb.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/media/usb/dvb-usb/usb-urb.c
b/drivers/media/usb/dvb-usb/usb-urb.c
index 8917360..96be721 100644
--- a/drivers/media/usb/dvb-usb/usb-urb.c
+++ b/drivers/media/usb/dvb-usb/usb-urb.c
@@ -117,7 +117,7 @@ static int usb_allocate_stream_buffers(struct
usb_data_stream *stream, int num,
for (stream->buf_num = 0; stream->buf_num < num; stream->buf_num++) {
deb_mem("allocating buffer %d\n",stream->buf_num);
if (( stream->buf_list[stream->buf_num] =
- usb_alloc_coherent(stream->udev, size,
GFP_ATOMIC,
+ usb_alloc_coherent(stream->udev, size,
GFP_KERNEL,
&stream->dma_addr[stream->buf_num]) )
== NULL) {
deb_mem("not enough memory for urb-buffer
allocation.\n");
usb_free_stream_buffers(stream);
--
1.9.1
