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| author | David Mosberger <davidm@egauge.net> | 2016-03-08 14:42:48 -0700 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2020-06-11 19:05:39 +0100 |
| commit | 371262ec7bbf0ffc4b2a66c3f7c9230ee5e6a2c5 (patch) | |
| tree | ed1cbf54dceddaf20e5819a4090833abfe550145 | |
| parent | 9592b90cdc99f58e0674e64037c422ea7e9aa367 (diff) | |
| download | linux-stable-371262ec7bbf0ffc4b2a66c3f7c9230ee5e6a2c5.tar.gz linux-stable-371262ec7bbf0ffc4b2a66c3f7c9230ee5e6a2c5.tar.bz2 linux-stable-371262ec7bbf0ffc4b2a66c3f7c9230ee5e6a2c5.zip | |
drivers: usb: core: Don't disable irqs in usb_sg_wait() during URB submit.
commit 98b74b0ee57af1bcb6e8b2e76e707a71c5ef8ec9 upstream.
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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
| -rw-r--r-- | drivers/usb/core/message.c | 15 |
1 files changed, 7 insertions, 8 deletions
diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c index f7019c7e9bc5..a3abe56898a9 100644 --- a/drivers/usb/core/message.c +++ b/drivers/usb/core/message.c @@ -306,9 +306,10 @@ static void sg_complete(struct urb *urb) */ spin_unlock(&io->lock); for (i = 0, found = 0; i < io->entries; i++) { - if (!io->urbs[i] || !io->urbs[i]->dev) + if (!io->urbs[i]) continue; if (found) { + usb_block_urb(io->urbs[i]); retval = usb_unlink_urb(io->urbs[i]); if (retval != -EINPROGRESS && retval != -ENODEV && @@ -519,12 +520,10 @@ void usb_sg_wait(struct usb_sg_request *io) int retval; io->urbs[i]->dev = io->dev; - retval = usb_submit_urb(io->urbs[i], GFP_ATOMIC); - - /* after we submit, let completions or cancellations fire; - * we handshake using io->status. - */ spin_unlock_irq(&io->lock); + + retval = usb_submit_urb(io->urbs[i], GFP_NOIO); + switch (retval) { /* maybe we retrying will recover */ case -ENXIO: /* hc didn't queue this one */ @@ -594,8 +593,8 @@ void usb_sg_cancel(struct usb_sg_request *io) for (i = 0; i < io->entries; i++) { int retval; - if (!io->urbs[i]->dev) - continue; + usb_block_urb(io->urbs[i]); + retval = usb_unlink_urb(io->urbs[i]); if (retval != -EINPROGRESS && retval != -ENODEV |