Some QMP command handlers can block the main loop for a relatively long
time, for example because they perform some I/O. This is quite nasty.
Allowing such handlers to run in a coroutine where they can yield (and
therefore release the BQL) while waiting for an event such as I/O
completion solves the problem.
This series adds the infrastructure to allow this and switches
block_resize to run in a coroutine as a first example.
This is an alternative solution to Marc-André's "monitor: add
asynchronous command type" series.
v4:
- Forbid 'oob': true, 'coroutine': true [Markus]
- Removed Python type hints [Markus]
- Introduced separate bool qmp_dispatcher_co_shutdown to make it clearer
how a shutdown request is signalled to the dispatcher [Markus]
- Allow using aio_poll() with iohandler_ctx and use that instead of
aio_bh_poll() [Markus]
- Removed coroutine_fn from qmp_block_resize() again because at least
one caller (HMP) calls it outside of coroutine context [Markus]
- Tried to make the synchronisation between dispatcher and the monitor
thread clearer, and fixed a race condition
- Improved documentation and comments
v3:
- Fix race between monitor thread and dispatcher that could schedule the
dispatcher coroutine twice if a second requests comes in before the
dispatcher can wake up [Patchew]
v2:
- Fix typo in a commit message [Eric]
- Use hyphen instead of underscore for the test command [Eric]
- Mark qmp_block_resize() as coroutine_fn [Stefan]
Kevin Wolf (4):
qapi: Add a 'coroutine' flag for commands
vl: Initialise main loop earlier
qmp: Move dispatcher to a coroutine
block: Mark 'block_resize' as coroutine
qapi/block-core.json| 3 +-
docs/devel/qapi-code-gen.txt| 10 +++
include/qapi/qmp/dispatch.h | 2 +
monitor/monitor-internal.h | 6 +-
monitor/monitor.c | 33 +--
monitor/qmp.c | 110 +---
qapi/qmp-dispatch.c | 44 +-
qapi/qmp-registry.c | 3 +
tests/test-qmp-cmds.c | 4 +
util/aio-posix.c| 7 +-
vl.c| 10 +--
scripts/qapi/commands.py| 10 ++-
scripts/qapi/doc.py | 2 +-
scripts/qapi/expr.py| 7 +-
scripts/qapi/introspect.py | 2 +-
scripts/qapi/schema.py | 9 +-
tests/qapi-schema/test-qapi.py | 7 +-
tests/Makefile.include | 1 +
tests/qapi-schema/oob-coroutine.err | 2 +
tests/qapi-schema/oob-coroutine.json| 2 +
tests/qapi-schema/oob-coroutine.out | 0
tests/qapi-schema/qapi-schema-test.json | 1 +
tests/qapi-schema/qapi-schema-test.out | 2 +
23 files changed, 216 insertions(+), 61 deletions(-)
create mode 100644 tests/qapi-schema/oob-coroutine.err
create mode 100644 tests/qapi-schema/oob-coroutine.json
create mode 100644 tests/qapi-schema/oob-coroutine.out
--
2.20.1
