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
