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98b74b0ee5
usb_submit_urb() may take quite long to execute. For example, a single sg list may have 30 or more entries, possibly leading to that many calls to DMA-map pages. This can cause interrupt latency of several hundred micro-seconds. Avoid the problem by releasing the io->lock spinlock and re-enabling interrupts before calling usb_submit_urb(). This opens races with usb_sg_cancel() and sg_complete(). Handle those races by using usb_block_urb() to stop URBs from being submitted after usb_sg_cancel() or sg_complete() with error. Note that usb_unlink_urb() is guaranteed to return -ENODEV if !io->urbs[i]->dev and since the -ENODEV case is already handled, we don't have to check for !io->urbs[i]->dev explicitly. Before this change, reading 512MB from an ext3 filesystem on a USB memory stick showed a throughput of 12 MB/s with about 500 missed deadlines. With this change, reading the same file gave the same throughput but only one or two missed deadlines. Signed-off-by: David Mosberger <davidm@egauge.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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| .. | ||
| buffer.c | ||
| config.c | ||
| devices.c | ||
| devio.c | ||
| driver.c | ||
| endpoint.c | ||
| file.c | ||
| generic.c | ||
| hcd-pci.c | ||
| hcd.c | ||
| hub.c | ||
| hub.h | ||
| Kconfig | ||
| Makefile | ||
| message.c | ||
| notify.c | ||
| of.c | ||
| otg_whitelist.h | ||
| port.c | ||
| quirks.c | ||
| sysfs.c | ||
| urb.c | ||
| usb-acpi.c | ||
| usb.c | ||
| usb.h | ||