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[Qemu-devel] [PULL v2 06/24] io: make qio_channel_yield aware of AioCont
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PULL v2 06/24] io: make qio_channel_yield aware of AioContexts |
Date: |
Tue, 21 Feb 2017 11:56:26 +0000 |
From: Paolo Bonzini <address@hidden>
Support separate coroutines for reading and writing, and place the
read/write handlers on the AioContext that the QIOChannel is registered
with.
Reviewed-by: Daniel P. Berrange <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
Reviewed-by: Fam Zheng <address@hidden>
Message-id: address@hidden
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
include/io/channel.h | 47 ++++++++++++++++++++++++++--
io/channel.c | 86 +++++++++++++++++++++++++++++++++++++++-------------
2 files changed, 109 insertions(+), 24 deletions(-)
diff --git a/include/io/channel.h b/include/io/channel.h
index 0bc7c3f..5d48906 100644
--- a/include/io/channel.h
+++ b/include/io/channel.h
@@ -23,6 +23,7 @@
#include "qemu-common.h"
#include "qom/object.h"
+#include "qemu/coroutine.h"
#include "block/aio.h"
#define TYPE_QIO_CHANNEL "qio-channel"
@@ -81,6 +82,9 @@ struct QIOChannel {
Object parent;
unsigned int features; /* bitmask of QIOChannelFeatures */
char *name;
+ AioContext *ctx;
+ Coroutine *read_coroutine;
+ Coroutine *write_coroutine;
#ifdef _WIN32
HANDLE event; /* For use with GSource on Win32 */
#endif
@@ -503,13 +507,50 @@ guint qio_channel_add_watch(QIOChannel *ioc,
/**
+ * qio_channel_attach_aio_context:
+ * @ioc: the channel object
+ * @ctx: the #AioContext to set the handlers on
+ *
+ * Request that qio_channel_yield() sets I/O handlers on
+ * the given #AioContext. If @ctx is %NULL, qio_channel_yield()
+ * uses QEMU's main thread event loop.
+ *
+ * You can move a #QIOChannel from one #AioContext to another even if
+ * I/O handlers are set for a coroutine. However, #QIOChannel provides
+ * no synchronization between the calls to qio_channel_yield() and
+ * qio_channel_attach_aio_context().
+ *
+ * Therefore you should first call qio_channel_detach_aio_context()
+ * to ensure that the coroutine is not entered concurrently. Then,
+ * while the coroutine has yielded, call qio_channel_attach_aio_context(),
+ * and then aio_co_schedule() to place the coroutine on the new
+ * #AioContext. The calls to qio_channel_detach_aio_context()
+ * and qio_channel_attach_aio_context() should be protected with
+ * aio_context_acquire() and aio_context_release().
+ */
+void qio_channel_attach_aio_context(QIOChannel *ioc,
+ AioContext *ctx);
+
+/**
+ * qio_channel_detach_aio_context:
+ * @ioc: the channel object
+ *
+ * Disable any I/O handlers set by qio_channel_yield(). With the
+ * help of aio_co_schedule(), this allows moving a coroutine that was
+ * paused by qio_channel_yield() to another context.
+ */
+void qio_channel_detach_aio_context(QIOChannel *ioc);
+
+/**
* qio_channel_yield:
* @ioc: the channel object
* @condition: the I/O condition to wait for
*
- * Yields execution from the current coroutine until
- * the condition indicated by @condition becomes
- * available.
+ * Yields execution from the current coroutine until the condition
+ * indicated by @condition becomes available. @condition must
+ * be either %G_IO_IN or %G_IO_OUT; it cannot contain both. In
+ * addition, no two coroutine can be waiting on the same condition
+ * and channel at the same time.
*
* This must only be called from coroutine context
*/
diff --git a/io/channel.c b/io/channel.c
index ce470d7..cdf7454 100644
--- a/io/channel.c
+++ b/io/channel.c
@@ -21,7 +21,7 @@
#include "qemu/osdep.h"
#include "io/channel.h"
#include "qapi/error.h"
-#include "qemu/coroutine.h"
+#include "qemu/main-loop.h"
bool qio_channel_has_feature(QIOChannel *ioc,
QIOChannelFeature feature)
@@ -238,36 +238,80 @@ off_t qio_channel_io_seek(QIOChannel *ioc,
}
-typedef struct QIOChannelYieldData QIOChannelYieldData;
-struct QIOChannelYieldData {
- QIOChannel *ioc;
- Coroutine *co;
-};
+static void qio_channel_set_aio_fd_handlers(QIOChannel *ioc);
+static void qio_channel_restart_read(void *opaque)
+{
+ QIOChannel *ioc = opaque;
+ Coroutine *co = ioc->read_coroutine;
+
+ ioc->read_coroutine = NULL;
+ qio_channel_set_aio_fd_handlers(ioc);
+ aio_co_wake(co);
+}
-static gboolean qio_channel_yield_enter(QIOChannel *ioc,
- GIOCondition condition,
- gpointer opaque)
+static void qio_channel_restart_write(void *opaque)
{
- QIOChannelYieldData *data = opaque;
- qemu_coroutine_enter(data->co);
- return FALSE;
+ QIOChannel *ioc = opaque;
+ Coroutine *co = ioc->write_coroutine;
+
+ ioc->write_coroutine = NULL;
+ qio_channel_set_aio_fd_handlers(ioc);
+ aio_co_wake(co);
}
+static void qio_channel_set_aio_fd_handlers(QIOChannel *ioc)
+{
+ IOHandler *rd_handler = NULL, *wr_handler = NULL;
+ AioContext *ctx;
+
+ if (ioc->read_coroutine) {
+ rd_handler = qio_channel_restart_read;
+ }
+ if (ioc->write_coroutine) {
+ wr_handler = qio_channel_restart_write;
+ }
+
+ ctx = ioc->ctx ? ioc->ctx : iohandler_get_aio_context();
+ qio_channel_set_aio_fd_handler(ioc, ctx, rd_handler, wr_handler, ioc);
+}
+
+void qio_channel_attach_aio_context(QIOChannel *ioc,
+ AioContext *ctx)
+{
+ AioContext *old_ctx;
+ if (ioc->ctx == ctx) {
+ return;
+ }
+
+ old_ctx = ioc->ctx ? ioc->ctx : iohandler_get_aio_context();
+ qio_channel_set_aio_fd_handler(ioc, old_ctx, NULL, NULL, NULL);
+ ioc->ctx = ctx;
+ qio_channel_set_aio_fd_handlers(ioc);
+}
+
+void qio_channel_detach_aio_context(QIOChannel *ioc)
+{
+ ioc->read_coroutine = NULL;
+ ioc->write_coroutine = NULL;
+ qio_channel_set_aio_fd_handlers(ioc);
+ ioc->ctx = NULL;
+}
void coroutine_fn qio_channel_yield(QIOChannel *ioc,
GIOCondition condition)
{
- QIOChannelYieldData data;
-
assert(qemu_in_coroutine());
- data.ioc = ioc;
- data.co = qemu_coroutine_self();
- qio_channel_add_watch(ioc,
- condition,
- qio_channel_yield_enter,
- &data,
- NULL);
+ if (condition == G_IO_IN) {
+ assert(!ioc->read_coroutine);
+ ioc->read_coroutine = qemu_coroutine_self();
+ } else if (condition == G_IO_OUT) {
+ assert(!ioc->write_coroutine);
+ ioc->write_coroutine = qemu_coroutine_self();
+ } else {
+ abort();
+ }
+ qio_channel_set_aio_fd_handlers(ioc);
qemu_coroutine_yield();
}
--
2.9.3
- [Qemu-devel] [PULL v2 00/24] Block patches, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 01/24] block: move AioContext, QEMUTimer, main-loop to libqemuutil, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 03/24] block-backend: allow blk_prw from coroutine context, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 02/24] aio: introduce aio_co_schedule and aio_co_wake, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 04/24] test-thread-pool: use generic AioContext infrastructure, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 05/24] io: add methods to set I/O handlers on AioContext, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 06/24] io: make qio_channel_yield aware of AioContexts,
Stefan Hajnoczi <=
- [Qemu-devel] [PULL v2 09/24] blkdebug: reschedule coroutine on the AioContext it is running on, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 08/24] coroutine-lock: reschedule coroutine on the AioContext it was running on, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 10/24] qed: introduce qed_aio_start_io and qed_aio_next_io_cb, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 11/24] aio: push aio_context_acquire/release down to dispatching, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 07/24] nbd: convert to use qio_channel_yield, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 12/24] block: explicitly acquire aiocontext in timers that need it, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 13/24] block: explicitly acquire aiocontext in callbacks that need it, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 14/24] block: explicitly acquire aiocontext in bottom halves that need it, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 15/24] block: explicitly acquire aiocontext in aio callbacks that need it, Stefan Hajnoczi, 2017/02/21
- [Qemu-devel] [PULL v2 17/24] async: remove unnecessary inc/dec pairs, Stefan Hajnoczi, 2017/02/21