[PATCH v2] mm: dmapool: use provided gfp flags for all dma_alloc_coherent() calls
From: arnd@arndb.de (Arnd Bergmann)
Date: 2013-01-22 18:15:05
Also in:
linux-mm, lkml
Subsystem:
em28xx video4linux driver, media input infrastructure (v4l/dvb), the rest · Maintainers:
Mauro Carvalho Chehab, Linus Torvalds
On Monday 21 January 2013, Greg KH wrote:
quoted
I don't know a lot about USB, but I always assumed that this was not a normal condition and that there are only a couple of URBs per endpoint used at a time. Maybe Greg or someone else with a USB background can shed some light on this.There's no restriction on how many URBs a driver can have outstanding at once, and if you have a system with a lot of USB devices running at the same time, there could be lots of URBs in flight depending on the number of host controllers and devices and drivers being used.
Ok, thanks for clarifying that. I read some more of the em28xx driver, and while it does have a bunch of URBs in flight, there are only five audio and five video URBs that I see simultaneously being submitted, and then resubmitted from their completion handlers. I think this means that there should be 10 URBs active at any given time in this driver, which does not explain why we get 256 allocations. I also noticed that the initial submissions are all atomic but don't need to, so it may be worth trying the patch below, which should also help in low-memory situations. We could also try moving the resubmission into a workqueue in order to let those be GFP_KERNEL, but I don't think that will help. Arnd
diff --git a/drivers/media/usb/em28xx/em28xx-audio.c b/drivers/media/usb/em28xx/em28xx-audio.c
index 2fdb66e..8b789f4 100644
--- a/drivers/media/usb/em28xx/em28xx-audio.c
+++ b/drivers/media/usb/em28xx/em28xx-audio.c@@ -177,12 +177,12 @@ static int em28xx_init_audio_isoc(struct em28xx *dev) struct urb *urb; int j, k; - dev->adev.transfer_buffer[i] = kmalloc(sb_size, GFP_ATOMIC); + dev->adev.transfer_buffer[i] = kmalloc(sb_size, GFP_KERNEL); if (!dev->adev.transfer_buffer[i]) return -ENOMEM; memset(dev->adev.transfer_buffer[i], 0x80, sb_size); - urb = usb_alloc_urb(EM28XX_NUM_AUDIO_PACKETS, GFP_ATOMIC); + urb = usb_alloc_urb(EM28XX_NUM_AUDIO_PACKETS, GFP_KERNEL); if (!urb) { em28xx_errdev("usb_alloc_urb failed!\n"); for (j = 0; j < i; j++) {
@@ -212,7 +212,7 @@ static int em28xx_init_audio_isoc(struct em28xx *dev) } for (i = 0; i < EM28XX_AUDIO_BUFS; i++) { - errCode = usb_submit_urb(dev->adev.urb[i], GFP_ATOMIC); + errCode = usb_submit_urb(dev->adev.urb[i], GFP_KERNEL); if (errCode) { em28xx_errdev("submit of audio urb failed\n"); em28xx_deinit_isoc_audio(dev);
diff --git a/drivers/media/usb/em28xx/em28xx-core.c b/drivers/media/usb/em28xx/em28xx-core.c
index bed07a6..c5a2c4b 100644
--- a/drivers/media/usb/em28xx/em28xx-core.c
+++ b/drivers/media/usb/em28xx/em28xx-core.c@@ -1166,7 +1166,7 @@ int em28xx_init_isoc(struct em28xx *dev, enum em28xx_mode mode, /* submit urbs and enables IRQ */ for (i = 0; i < isoc_bufs->num_bufs; i++) { - rc = usb_submit_urb(isoc_bufs->urb[i], GFP_ATOMIC); + rc = usb_submit_urb(isoc_bufs->urb[i], GFP_KERNEL); if (rc) { em28xx_err("submit of urb %i failed (error=%i)\n", i, rc);