From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58088) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eGufL-0003ks-RP for qemu-devel@nongnu.org; Mon, 20 Nov 2017 17:35:49 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eGufK-0001Il-Mr for qemu-devel@nongnu.org; Mon, 20 Nov 2017 17:35:47 -0500 Date: Mon, 20 Nov 2017 17:35:36 -0500 From: Jeff Cody Message-ID: <20171120223536.GC32161@localhost.localdomain> References: <0c039d00e03331d863ee249810d9778313670803.1511145863.git.jcody@redhat.com> <06d8393e-8422-0576-ad68-f14e49eed1a6@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <06d8393e-8422-0576-ad68-f14e49eed1a6@redhat.com> Subject: Re: [Qemu-devel] [PATCH 3/5] coroutines: abort if we try to enter a still-sleeping coroutine List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, mreitz@redhat.com, stefanha@redhat.com, famz@redhat.com, kwolf@redhat.com On Mon, Nov 20, 2017 at 11:30:39PM +0100, Paolo Bonzini wrote: > On 20/11/2017 03:46, Jeff Cody wrote: > > Once a coroutine is "sleeping", the timer callback will either enter the > > coroutine, or schedule it for the next AioContext if using iothreads. > > > > It is illegal to enter that coroutine while waiting for this timer > > event and subsequent callback. This patch will catch such an attempt, > > and abort QEMU with an error. > > > > Like with the previous patch, we cannot rely solely on the co->caller > > check for recursive entry. The prematurely entered coroutine may exit > > with COROUTINE_TERMINATE before the timer expires, making co->caller no > > longer valid. > > > > We can clear co->sleeping in in co_sleep_cb(), because any doubly entry > > attempt after point should be caught by either the co->scheduled or > > co->caller checks. > > > > Signed-off-by: Jeff Cody > > --- > > include/qemu/coroutine_int.h | 2 ++ > > util/qemu-coroutine-sleep.c | 3 +++ > > util/qemu-coroutine.c | 5 +++++ > > 3 files changed, 10 insertions(+) > > > > diff --git a/include/qemu/coroutine_int.h b/include/qemu/coroutine_int.h > > index 931cdc9..b071217 100644 > > --- a/include/qemu/coroutine_int.h > > +++ b/include/qemu/coroutine_int.h > > @@ -56,6 +56,8 @@ struct Coroutine { > > > > int scheduled; > > > > + int sleeping; > > Is this a different "state" (in Stefan's parlance) than scheduled? In > practice both means that someone may call qemu_(aio_)coroutine_enter > concurrently, so you'd better not do it yourself. > It is slightly different; it is from sleeping with a timer via co_aio_sleep_ns and waking via co_sleep_cb. Whereas the 'co->scheduled' is specifically from being scheduled for a specific AioContext, via aio_co_schedule(). In practice, 'co->schedule' and 'co->sleeping' certainly rhyme, at the very least. But having them separate will put the abort closer to where the problem lies, so it should make debugging a bit easier if we hit it. > > > + > > QSIMPLEQ_ENTRY(Coroutine) co_queue_next; > > QSLIST_ENTRY(Coroutine) co_scheduled_next; > > }; > > diff --git a/util/qemu-coroutine-sleep.c b/util/qemu-coroutine-sleep.c > > index 9c56550..11ae95a 100644 > > --- a/util/qemu-coroutine-sleep.c > > +++ b/util/qemu-coroutine-sleep.c > > @@ -13,6 +13,7 @@ > > > > #include "qemu/osdep.h" > > #include "qemu/coroutine.h" > > +#include "qemu/coroutine_int.h" > > #include "qemu/timer.h" > > #include "block/aio.h" > > > > @@ -25,6 +26,7 @@ static void co_sleep_cb(void *opaque) > > { > > CoSleepCB *sleep_cb = opaque; > > > > + sleep_cb->co->sleeping = 0; > > aio_co_wake(sleep_cb->co); > > } > > > > @@ -34,6 +36,7 @@ void coroutine_fn co_aio_sleep_ns(AioContext *ctx, QEMUClockType type, > > CoSleepCB sleep_cb = { > > .co = qemu_coroutine_self(), > > }; > > + sleep_cb.co->sleeping = 1; > > 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(); > > diff --git a/util/qemu-coroutine.c b/util/qemu-coroutine.c > > index 2edab63..1d9f93d 100644 > > --- a/util/qemu-coroutine.c > > +++ b/util/qemu-coroutine.c > > @@ -118,6 +118,11 @@ void qemu_aio_coroutine_enter(AioContext *ctx, Coroutine *co) > > abort(); > > } > > > > + if (co->sleeping == 1) { > > + fprintf(stderr, "Cannot enter a co-routine that is still sleeping\n"); > > + abort(); > > + } > > + > > if (co->caller) { > > fprintf(stderr, "Co-routine re-entered recursively\n"); > > abort(); > > >