coroutine-lock: make qemu_co_enter_next thread-safe

qemu_co_queue_next does not need to release and re-acquire the mutex,
because the queued coroutine does not run immediately.  However, this
does not hold for qemu_co_enter_next.  Now that qemu_co_queue_wait
can synchronize (via QemuLockable) with code that is not running in
coroutine context, it's important that code using qemu_co_enter_next
can easily use a standardized locking idiom.

First of all, qemu_co_enter_next must use aio_co_wake to restart the
coroutine.  Second, the function gains a second argument, a QemuLockable*,
and the comments of qemu_co_queue_next and qemu_co_queue_restart_all
are adjusted to clarify the difference.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20180203153935.8056-5-pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/fsdev/qemu-fsdev-throttle.c b/fsdev/qemu-fsdev-throttle.c
index 49eebb5412..1dc07fbc12 100644
--- a/fsdev/qemu-fsdev-throttle.c
+++ b/fsdev/qemu-fsdev-throttle.c
@@ -20,13 +20,13 @@
 static void fsdev_throttle_read_timer_cb(void *opaque)
 {
     FsThrottle *fst = opaque;
-    qemu_co_enter_next(&fst->throttled_reqs[false]);
+    qemu_co_enter_next(&fst->throttled_reqs[false], NULL);
 }
 
 static void fsdev_throttle_write_timer_cb(void *opaque)
 {
     FsThrottle *fst = opaque;
-    qemu_co_enter_next(&fst->throttled_reqs[true]);
+    qemu_co_enter_next(&fst->throttled_reqs[true], NULL);
 }
 
 void fsdev_throttle_parse_opts(QemuOpts *opts, FsThrottle *fst, Error **errp)