diff options
| -rw-r--r-- | util/ec3po/threadproc_shim.py | 41 |
1 files changed, 40 insertions, 1 deletions
diff --git a/util/ec3po/threadproc_shim.py b/util/ec3po/threadproc_shim.py index ab8ba7b897..5edbf0dd89 100644 --- a/util/ec3po/threadproc_shim.py +++ b/util/ec3po/threadproc_shim.py @@ -16,14 +16,53 @@ TODO(b/79684405): After both platform/ec/ and third_party/hdctools/ sides of ec3po have been updated to use this library, replace the multiprocessing implementations with threading-oriented equivalents. +TODO(b/79684405): Stop using multiprocessing.Pipe. The +multiprocessing.Connection objects it returns serialize and deserialize objects +(via Python pickling), which is necessary for sending them between processes, +but is unnecessary overhead between threads. This will not be a simple change, +because the ec3po Console and Interpreter classes use the underlying pipe/socket +pairs with select/poll/epoll alongside other file descriptors. A drop-in +replacement would be non-trivial and add undesirable complexity. The correct +solution will be to split off the polling of the pipes/queues from this module +into separate threads, so that they can be transitioned to another form of +cross-thread synchronization, e.g. directly waiting on Queue.Queue.get() or a +lower-level thread synchronization primitive. + TODO(b/79684405): After this library has been updated to contain threading-oriented equivalents to its original multiprocessing implementations, and some reasonable amount of time has elapsed for thread-based ec3po problems to be discovered, migrate both the platform/ec/ and third_party/hdctools/ sides -of ec3po off of this shim and then delete this file. +of ec3po off of this shim and then delete this file. IMPORTANT: This should +wait until after completing the TODO above to stop using multiprocessing.Pipe! """ +# Imports to bring objects into this namespace for users of this module. from multiprocessing import Pipe from multiprocessing import Process as ThreadOrProcess from multiprocessing import Queue from multiprocessing import Value + +# True if this module has ec3po using subprocesses, False if using threads. +# TODO(b/79684405): Change to False when switching to threading. +USING_SUBPROCS = True + + +def _DoNothing(): + """Do-nothing function for use as a callback with DoIf().""" + + +def DoIf(subprocs=_DoNothing, threads=_DoNothing): + """Return a callback or not based on ec3po use of subprocesses or threads. + + Args: + subprocs: callback that does not require any args - This will be returned + (not called!) if and only if ec3po is using subprocesses. This is + OPTIONAL, the default value is a do-nothing callback that returns None. + threads: callback that does not require any args - This will be returned + (not called!) if and only if ec3po is using threads. This is OPTIONAL, + the default value is a do-nothing callback that returns None. + + Returns: + Either the subprocs or threads argument will be returned. + """ + return subprocs if USING_SUBPROCS else threads |