From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50566) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eGmLh-0001ug-GK for qemu-devel@nongnu.org; Mon, 20 Nov 2017 08:42:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eGmLg-00050D-Kw for qemu-devel@nongnu.org; Mon, 20 Nov 2017 08:42:57 -0500 Date: Mon, 20 Nov 2017 08:42:40 -0500 From: Jeff Cody Message-ID: <20171120134240.GH5399@localhost.localdomain> References: <5bec37564f83e39e216d2ebcf7a380b0c7704e0e.1511145863.git.jcody@redhat.com> <20171120112826.GC4516@stefanha-x1.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171120112826.GC4516@stefanha-x1.localdomain> Subject: Re: [Qemu-devel] [Qemu-block] [PATCH 2/5] coroutine: abort if we try to enter coroutine scheduled for another ctx List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, kwolf@redhat.com, famz@redhat.com, qemu-block@nongnu.org, mreitz@redhat.com, stefanha@redhat.com, pbonzini@redhat.com On Mon, Nov 20, 2017 at 11:28:26AM +0000, Stefan Hajnoczi wrote: > On Sun, Nov 19, 2017 at 09:46:43PM -0500, Jeff Cody wrote: > > diff --git a/include/qemu/coroutine_int.h b/include/qemu/coroutine_int.h > > index cb98892..931cdc9 100644 > > --- a/include/qemu/coroutine_int.h > > +++ b/include/qemu/coroutine_int.h > > @@ -53,6 +53,9 @@ struct Coroutine { > > > > /* Only used when the coroutine has yielded. */ > > AioContext *ctx; > > + > > + int scheduled; > > s/int/bool/ > OK. > > diff --git a/util/qemu-coroutine.c b/util/qemu-coroutine.c > > index d6095c1..2edab63 100644 > > --- a/util/qemu-coroutine.c > > +++ b/util/qemu-coroutine.c > > @@ -109,6 +109,15 @@ void qemu_aio_coroutine_enter(AioContext *ctx, Coroutine *co) > > > > trace_qemu_aio_coroutine_enter(ctx, self, co, co->entry_arg); > > > > + /* if the Coroutine has already been scheduled, entering it again will > > + * cause us to enter it twice, potentially even after the coroutine has > > + * been deleted */ > > + if (co->scheduled == 1) { > > + fprintf(stderr, "Cannot enter a co-routine that has already " > > + "been scheduled to run in a different AioContext\n"); > > This error message is too specific, the AioContext doesn't have to be > different from the current one: > > block/blkdebug.c: aio_co_schedule(qemu_get_current_aio_context(), qemu_coroutine_self()); > > If something calls qemu_aio_coroutine_enter() on the coroutine it might > be from the same AioContext - but still an error condition worth failing > loudly on. > Good point. > I suggest simplifying the error message: > > fprintf(stderr, "Cannot enter a co-routine that has already " > "been scheduled\n"); OK. I'll also change the wording here to what you have above, as well: void aio_co_schedule(AioContext *ctx, Coroutine *co) { trace_aio_co_schedule(ctx, co); + if (co->scheduled == 1) { + fprintf(stderr, + "Cannot schedule a co-routine that is already scheduled\n"); + abort(); + } + co->scheduled = 1; QSLIST_INSERT_HEAD_ATOMIC(&ctx->scheduled_coroutines, co, co_scheduled_next); Jeff