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base repository: GlasgowEmbedded/glasgow
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head repository: GlasgowEmbedded/glasgow
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compare: a7d041f4ca58
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  • 2 commits
  • 2 files changed
  • 1 contributor

Commits on Jul 28, 2020

  1. access.direct.demultiplexer: fix a few typos in comments. NFC.

    @whitequark
    whitequark committed Jul 28, 2020
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    2917a10 View commit details

  2. support.task_queue: improve cancellation support. 

      * Propagate cancellation out of poll(), wait_one(), and wait_all().
  * Make cancel() an async function that waits until cancellation
    is finished.

Before this commit, cancelling a demultiplexer read (e.g. with ^C)
that was waiting on USB would cause it to fail an assert. After this
commit, the read is also cancelled.
    @whitequark
    whitequark committed Jul 28, 2020
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    a7d041f View commit details
Showing with 16 additions and 19 deletions.
  1. +7 −10 software/glasgow/access/direct/demultiplexer.py
  2. +9 −9 software/glasgow/support/task_queue.py
17 changes: 7 additions & 10 deletions software/glasgow/access/direct/demultiplexer.py
View file
Original file line number Diff line number Diff line change
@@ -23,10 +23,10 @@
# On the other hand, we would like to prevent programs from submitting a
# lot of small URBs and using up all the DMA-able kernel memory. [...]
#
# In other words, there is be a platform-specific limit for USB I/O size, which is not
# discoverable via libusb, and hitting which does not result in a sensible error returned
# from libusb (it returns LIBUSB_ERROR_IO even though USBDEVFS_SUBMITURB ioctl correctly
# returns -ENOMEM), so it is not even possible to be optimistic and back off after hitting it.
# In other words, there is a platform-specific limit for USB I/O size, which is not discoverable
# via libusb, and hitting which does not result in a sensible error returned from libusb
# (it returns LIBUSB_ERROR_IO even though USBDEVFS_SUBMITURB ioctl correctly returns -ENOMEM),
# so it is not even possible to be optimistic and back off after hitting it.
#
# To deal with this, use requests of at most 1024 EP buffer sizes (512 KiB with the FX2) as
# an arbitrary cutoff, and hope for the best.
@@ -54,7 +54,7 @@
# a single fixed value works.
_packets_per_xfer = 32

# Queue as many transfers as we can, but no more than 10, as the returns beyond that point
# Queue as many transfers as we can, but no more than 16, as the returns beyond that point
# are diminishing.
_xfers_per_queue = min(16, _max_packets_per_ep // _packets_per_xfer)

@@ -180,11 +180,8 @@ def __init__(self, device, applet, mux_interface,
async def cancel(self):
if self._in_tasks or self._out_tasks:
self.logger.trace("FIFO: cancelling operations")
self._in_tasks .cancel()
self._out_tasks.cancel()
# libusb cancellation is asynchronous, so wait until it's actually done.
await self._in_tasks .wait_all()
await self._out_tasks.wait_all()
await self._in_tasks .cancel()
await self._out_tasks.cancel()

async def reset(self):
await self.cancel()
18 changes: 9 additions & 9 deletions software/glasgow/support/task_queue.py
View file
Original file line number Diff line number Diff line change
@@ -21,8 +21,7 @@ def __init__(self):

def _callback(self, future):
self._live.remove(future)
if not future.cancelled():
self._done.append(future)
self._done.append(future)

def submit(self, coro):
"""
@@ -33,16 +32,18 @@ def submit(self, coro):
self._live.add(future)
future.add_done_callback(self._callback)

def cancel(self):
async def cancel(self):
"""
Cancel all tasks in the queue.
Cancel all tasks in the queue, and wait until cancellation is finished.
"""
for task in self._live:
task.cancel()
if self._live:
await asyncio.wait(self._live, return_when=asyncio.ALL_COMPLETED)

async def poll(self):
"""
Await all finished tasks that have been submitted to the queue. Return ``True`` if there
Await all finished tasks that have been submitted to the queue. Returns ``True`` if there
were any finished tasks, ``False`` otherwise.
This method needs to be called regularly to ensure that exceptions are propagated upwards
@@ -56,20 +57,19 @@ async def poll(self):
async def wait_one(self):
"""
Await at least one task in the queue. If there are no finished tasks, waits until the first
pending task finishes. Equivalent to :meth:`poll` otherwise.
pending task finishes.
"""
if not self._done:
await asyncio.wait(self._live, return_when=asyncio.FIRST_COMPLETED)
assert len(self._done) > 0
return await self.poll()
await self.poll()

async def wait_all(self):
"""
Await all tasks in the queue, if any.
"""
if self._live:
await asyncio.wait(self._live, return_when=asyncio.ALL_COMPLETED)
return await self.poll()
await self.poll()

def __bool__(self):
return bool(self._live)