On 4/11/19 12:27 PM, Vladimir Sementsov-Ogievskiy wrote: > Introduce a function to gracefully wake-up a coroutine, sleeping in > qemu_co_sleep_ns() sleep.
Maybe:
Introduce a function to gracefully short-circuit the remainder of the
delay for a coroutine sleeping in qemu_co_sleep_ns().
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
> ---
> include/qemu/coroutine.h | 6 ++++++
> util/qemu-coroutine-sleep.c | 20 ++++++++++++++++----
> 2 files changed, 22 insertions(+), 4 deletions(-)
>
> diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h
> index 9801e7f5a4..ec765c26f0 100644
> --- a/include/qemu/coroutine.h
> +++ b/include/qemu/coroutine.h
> @@ -278,6 +278,12 @@ void qemu_co_rwlock_unlock(CoRwlock *lock);
> */
> void coroutine_fn qemu_co_sleep_ns(QEMUClockType type, int64_t ns);
>
> +/*
> + * Wake a coroutine if it is sleeping by qemu_co_sleep_ns. Timer will be
> + * deleted.
Maybe:
Wake a coroutine if it is sleeping in qemu_co_sleep_ns, and delete the
timer.
> +++ b/util/qemu-coroutine-sleep.c
> @@ -17,13 +17,24 @@
> #include "qemu/timer.h"
> #include "block/aio.h"
>
> +const char *qemu_co_sleep_ns__scheduled = "qemu_co_sleep_ns";
> +
> +void qemu_co_sleep_wake(Coroutine *co)
> +{
> + /* Write of schedule protected by barrier write in aio_co_schedule */
> + const char *scheduled = atomic_cmpxchg(&co->scheduled,
> + qemu_co_sleep_ns__scheduled,
> NULL);
> +
> + if (scheduled == qemu_co_sleep_ns__scheduled) {
> + aio_co_wake(co);
> + }
> +}
> +
> static void co_sleep_cb(void *opaque)
> {
> Coroutine *co = opaque;
>
> - /* Write of schedule protected by barrier write in aio_co_schedule */
> - atomic_set(&co->scheduled, NULL);
> - aio_co_wake(co);
> + qemu_co_sleep_wake(co);
> }
>
> void coroutine_fn qemu_co_sleep_ns(QEMUClockType type, int64_t ns)
> @@ -32,7 +43,8 @@ void coroutine_fn qemu_co_sleep_ns(QEMUClockType type,
> int64_t ns)
> QEMUTimer *ts;
> Coroutine *co = qemu_coroutine_self();
>
> - const char *scheduled = atomic_cmpxchg(&co->scheduled, NULL, __func__);
> + const char *scheduled = atomic_cmpxchg(&co->scheduled, NULL,
> + qemu_co_sleep_ns__scheduled);
> if (scheduled) {
> fprintf(stderr,
> "%s: Co-routine was already scheduled in '%s'\n",
>
Here, I'd rather get an additional review from anyone more familiar with
coroutine sleeps. I'm guessing that your intent is to request a maximum
timeout for a given operation to complete in, but to leave the sleep
loop early if the operation completes earlier. I don't know if any
existing coroutine code can be used to express that same idea.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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