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authorKevin Wolf <kwolf@redhat.com>2023-05-17 17:28:33 +0200
committerKevin Wolf <kwolf@redhat.com>2023-05-19 19:16:53 +0200
commit7c1f51bf38de8cea4ed5030467646c37b46edeb7 (patch)
tree0a1fb3424e3310217287f102b397d50ee2617f4b /io
parent80fc5d260002432628710f8b0c7cfc7d9b97bb9d (diff)
nbd/server: Fix drained_poll to wake coroutine in right AioContext
nbd_drained_poll() generally runs in the main thread, not whatever iothread the NBD server coroutine is meant to run in, so it can't directly reenter the coroutines to wake them up. The code seems to have the right intention, it specifies the correct AioContext when it calls qemu_aio_coroutine_enter(). However, this functions doesn't schedule the coroutine to run in that AioContext, but it assumes it is already called in the home thread of the AioContext. To fix this, add a new thread-safe qio_channel_wake_read() that can be called in the main thread to wake up the coroutine in its AioContext, and use this in nbd_drained_poll(). Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-Id: <20230517152834.277483-3-kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'io')
-rw-r--r--io/channel.c33
1 files changed, 27 insertions, 6 deletions
diff --git a/io/channel.c b/io/channel.c
index 375a130a39..72f0066af5 100644
--- a/io/channel.c
+++ b/io/channel.c
@@ -19,6 +19,7 @@
*/
#include "qemu/osdep.h"
+#include "block/aio-wait.h"
#include "io/channel.h"
#include "qapi/error.h"
#include "qemu/main-loop.h"
@@ -514,7 +515,11 @@ int qio_channel_flush(QIOChannel *ioc,
static void qio_channel_restart_read(void *opaque)
{
QIOChannel *ioc = opaque;
- Coroutine *co = ioc->read_coroutine;
+ Coroutine *co = qatomic_xchg(&ioc->read_coroutine, NULL);
+
+ if (!co) {
+ return;
+ }
/* Assert that aio_co_wake() reenters the coroutine directly */
assert(qemu_get_current_aio_context() ==
@@ -525,7 +530,11 @@ static void qio_channel_restart_read(void *opaque)
static void qio_channel_restart_write(void *opaque)
{
QIOChannel *ioc = opaque;
- Coroutine *co = ioc->write_coroutine;
+ Coroutine *co = qatomic_xchg(&ioc->write_coroutine, NULL);
+
+ if (!co) {
+ return;
+ }
/* Assert that aio_co_wake() reenters the coroutine directly */
assert(qemu_get_current_aio_context() ==
@@ -568,7 +577,11 @@ void qio_channel_detach_aio_context(QIOChannel *ioc)
void coroutine_fn qio_channel_yield(QIOChannel *ioc,
GIOCondition condition)
{
+ AioContext *ioc_ctx = ioc->ctx ?: qemu_get_aio_context();
+
assert(qemu_in_coroutine());
+ assert(in_aio_context_home_thread(ioc_ctx));
+
if (condition == G_IO_IN) {
assert(!ioc->read_coroutine);
ioc->read_coroutine = qemu_coroutine_self();
@@ -580,18 +593,26 @@ void coroutine_fn qio_channel_yield(QIOChannel *ioc,
}
qio_channel_set_aio_fd_handlers(ioc);
qemu_coroutine_yield();
+ assert(in_aio_context_home_thread(ioc_ctx));
/* Allow interrupting the operation by reentering the coroutine other than
* through the aio_fd_handlers. */
- if (condition == G_IO_IN && ioc->read_coroutine) {
- ioc->read_coroutine = NULL;
+ if (condition == G_IO_IN) {
+ assert(ioc->read_coroutine == NULL);
qio_channel_set_aio_fd_handlers(ioc);
- } else if (condition == G_IO_OUT && ioc->write_coroutine) {
- ioc->write_coroutine = NULL;
+ } else if (condition == G_IO_OUT) {
+ assert(ioc->write_coroutine == NULL);
qio_channel_set_aio_fd_handlers(ioc);
}
}
+void qio_channel_wake_read(QIOChannel *ioc)
+{
+ Coroutine *co = qatomic_xchg(&ioc->read_coroutine, NULL);
+ if (co) {
+ aio_co_wake(co);
+ }
+}
static gboolean qio_channel_wait_complete(QIOChannel *ioc,
GIOCondition condition,