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Re: [Qemu-trivial] [Qemu-devel] [PATCH] coroutine: Fix documentation of
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-trivial] [Qemu-devel] [PATCH] coroutine: Fix documentation of co_aio_sleep_ns() |
Date: |
Wed, 8 Nov 2017 17:36:21 +0000 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Wed, Nov 08, 2017 at 09:57:47AM -0600, Eric Blake wrote:
> On 11/08/2017 09:47 AM, Paolo Bonzini wrote:
> > On 08/11/2017 16:42, Stefan Hajnoczi wrote:
> >>> In any case, co_aio_sleep_ns()
> >>> + * does not affect the #AioContext where the current coroutine is
> >>> running,
> >>> + * as the coroutine will restart on the same #AioContext that it is
> >>> + * running on.
> >> I cannot parse the second sentence. What does "affecting" an AioContext
> >> mean? Does "where the current coroutine is running" simply mean "the
> >> caller"?
> >>
> >> What is it trying to say? My guess is: the caller will be resumed in
> >> the current AioContext, not the timer's AioContext.
> >
> > Yes, that is the intended meaning. Perhaps just s/current//.
>
> How about:
>
> This function uses timers and hence needs to know the event loop
> (#AioContext) to place the timer on. After the time elapses, the
> current coroutine will restart with the same #AioContext it is currently
> running in, even if that is different than the timer context passed to
> co_aio_sleep_ns().
These complicated semantics are a clue that the API should be
simplified. QEMU has changed since this function was first introduced.
Now we can do the following:
void coroutine_fn qemu_co_sleep_ns(QEMUClockType type, int64_t ns)
{
AioContext *ctx = qemu_get_current_aio_context();
CoSleepCB sleep_cb = {
.co = qemu_coroutine_self(),
};
sleep_cb.ts = aio_timer_new(ctx, type, SCALE_NS, co_sleep_cb, &sleep_cb);
timer_mod(sleep_cb.ts, qemu_clock_get_ns(type) + ns);
qemu_coroutine_yield();
timer_del(sleep_cb.ts);
timer_free(sleep_cb.ts);
}
I don't see a reason for the caller to pass in an AioContext.
Any objections? Will send a patch if this is okay.
Stefan
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