On Wed, Feb 01, 2017 at 04:05:15AM -0800, Paolo Bonzini wrote:
> This series pushes down aio_context_acquire/release to the point
> where we can actually reason on using different fine-grained mutexes.
>
> The main infrastructure is introduced in patch 2. The new API aio_co_wake
> starts a coroutine with aio_context_acquire/release protection, which
> requires tracking each coroutine's "home" AioContext. aio_co_schedule
> instead takes care of moving a sleeping coroutine to a different
> AioContext, also ensuring that it runs under aio_context_acquire/release.
> This is useful to implement bdrv_set_aio_context, as a simpler alternative
> to bottom halves. Even though one-shot BHs are already simpler than
> what we had before, after this patch aio_co_wake and aio_co_schedule
> save you from having to do aio_context_acquire/release explicitly.
>
> Ultimately, only a small number of aio_context_acquire/release pairs are
> added after the pushdown. These are mostly in drivers that use external
> libraries (and actually they could already be replaced by QemuMutex)
> and in device models that support multithreaded operation (aka iothread
> aka dataplane).
>
> Notably, coroutines need not care about aio_context_acquire/release.
> The device models ensure that the first creation of the coroutine has
> the AioContext, while aio_co_wake/aio_co_schedule do the same after
> they yield. Therefore, most of the files only need to use those two
> functions instead of, respectively, qemu_coroutine_enter and
> aio_bh_schedule_oneshot.
>
> However, this is only an intermediate step which is needed because the
> block layer and qemu-coroutine locks are thread-unsafe. So the next
> part will add separate locking, independent of AioContext, to block.c and
> mostly block/io.c---this includes making CoMutex thread-safe. Patch 17
> therefore already documents the current locking policies block.h to
> prepare for the next series.
>
> v2->v3:
> moved patch 4 ("block: move AioContext and QEMUTimer to libqemuutil")
> earlier due to rebase
> add coroutine_fn annotation in test-aio-multithread.c [Stefan]
> don't remove yield_until_fd_readable, will resubmit to trivial [Stefan]
> add comments about wake/yield sequence [Stefan]
> new patch 9 to fix an incorrect (in the future) use of aio_co_schedule
>
> v1->v2:
> new patch (4) removing block-obj-y -> io-obj-y dependency
> removed QIOChannelRestart from
> "io: add methods to set I/O handlers on AioContext"
> improved qio_channel_set_aio_context docs, renamed to
> qio_channel_attach_aio_context
> fixed pasto in "io: make qio_channel_yield aware of AioContexts"
> document restrictions in bdrv_aio_cancel due to qemu_aio_ref
> converted NBD server to qio_channel_yield too
> allow NULL s->read_reply_co
>
>
> Paolo Bonzini (18):
> block: move AioContext and QEMUTimer to libqemuutil
> aio: introduce aio_co_schedule and aio_co_wake
> block-backend: allow blk_prw from coroutine context
> test-thread-pool: use generic AioContext infrastructure
> io: add methods to set I/O handlers on AioContext
> io: make qio_channel_yield aware of AioContexts
> nbd: convert to use qio_channel_yield
> coroutine-lock: reschedule coroutine on the AioContext it was running
> on
> blkdebug: reschedule coroutine on the AioContext it is running on
> qed: introduce qed_aio_start_io and qed_aio_next_io_cb
> aio: push aio_context_acquire/release down to dispatching
> block: explicitly acquire aiocontext in timers that need it
> block: explicitly acquire aiocontext in callbacks that need it
> block: explicitly acquire aiocontext in bottom halves that need it
> block: explicitly acquire aiocontext in aio callbacks that need it
> aio-posix: partially inline aio_dispatch into aio_poll
> async: remove unnecessary inc/dec pairs
> block: document fields protected by AioContext lock
>
> Makefile.objs | 4 -
> block/blkdebug.c | 9 +-
> block/blkreplay.c | 2 +-
> block/block-backend.c | 13 ++-
> block/curl.c | 44 ++++++--
> block/gluster.c | 9 +-
> block/io.c | 38 ++-----
> block/iscsi.c | 15 ++-
> block/linux-aio.c | 10 +-
> block/mirror.c | 12 +-
> block/nbd-client.c | 117 +++++++++-----------
> block/nbd-client.h | 2 +-
> block/nfs.c | 9 +-
> block/qed-cluster.c | 2 +
> block/qed-table.c | 12 +-
> block/qed.c | 58 +++++++---
> block/qed.h | 3 +
> block/sheepdog.c | 29 ++---
> block/ssh.c | 29 ++---
> block/throttle-groups.c | 2 +
> block/win32-aio.c | 9 +-
> dma-helpers.c | 2 +
> hw/block/virtio-blk.c | 19 +++-
> hw/scsi/scsi-bus.c | 2 +
> hw/scsi/scsi-disk.c | 15 +++
> hw/scsi/scsi-generic.c | 20 +++-
> hw/scsi/virtio-scsi.c | 6 +
> include/block/aio.h | 38 ++++++-
> include/block/block_int.h | 64 ++++++-----
> include/io/channel.h | 72 +++++++++++-
> include/qemu/coroutine_int.h | 11 +-
> include/sysemu/block-backend.h | 14 ++-
> io/channel-command.c | 13 +++
> io/channel-file.c | 11 ++
> io/channel-socket.c | 16 ++-
> io/channel-tls.c | 12 ++
> io/channel-watch.c | 6 +
> io/channel.c | 97 ++++++++++++----
> nbd/client.c | 2 +-
> nbd/common.c | 9 +-
> nbd/server.c | 94 +++++-----------
> stubs/Makefile.objs | 1 +
> stubs/linux-aio.c | 32 ++++++
> stubs/set-fd-handler.c | 11 --
> tests/Makefile.include | 18 +--
> tests/iothread.c | 91 +++++++++++++++
> tests/iothread.h | 25 +++++
> tests/test-aio-multithread.c | 213 ++++++++++++++++++++++++++++++++++++
> tests/test-thread-pool.c | 12 +-
> trace-events | 4 +
> util/Makefile.objs | 6 +-
> aio-posix.c => util/aio-posix.c | 60 +++-------
> aio-win32.c => util/aio-win32.c | 30 ++---
> util/aiocb.c | 55 ++++++++++
> async.c => util/async.c | 84 ++++++++++++--
> iohandler.c => util/iohandler.c | 0
> main-loop.c => util/main-loop.c | 0
> util/qemu-coroutine-lock.c | 5 +-
> util/qemu-coroutine-sleep.c | 2 +-
> util/qemu-coroutine.c | 8 ++
> qemu-timer.c => util/qemu-timer.c | 0
> thread-pool.c => util/thread-pool.c | 6 +-
> util/trace-events | 1 -
> 63 files changed, 1166 insertions(+), 454 deletions(-)
> create mode 100644 stubs/linux-aio.c
> create mode 100644 tests/iothread.c
> create mode 100644 tests/iothread.h
> create mode 100644 tests/test-aio-multithread.c
> rename aio-posix.c => util/aio-posix.c (94%)
> rename aio-win32.c => util/aio-win32.c (95%)
> create mode 100644 util/aiocb.c
> rename async.c => util/async.c (82%)
> rename iohandler.c => util/iohandler.c (100%)
> rename main-loop.c => util/main-loop.c (100%)
> rename qemu-timer.c => util/qemu-timer.c (100%)
> rename thread-pool.c => util/thread-pool.c (98%)
Please rebase.
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>