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Wed, 18 Mar 2020 15:36:15 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-112-130.ams2.redhat.com [10.36.112.130]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E082860BEC; Wed, 18 Mar 2020 15:36:14 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id DD1AA1138404; Wed, 18 Mar 2020 16:36:12 +0100 (CET) From: Markus Armbruster To: Kevin Wolf Subject: Re: [PATCH v5 3/4] qmp: Move dispatcher to a coroutine References: <20200218154036.28562-1-kwolf@redhat.com> <20200218154036.28562-4-kwolf@redhat.com> Date: Wed, 18 Mar 2020 16:36:12 +0100 In-Reply-To: <20200218154036.28562-4-kwolf@redhat.com> (Kevin Wolf's message of "Tue, 18 Feb 2020 16:40:35 +0100") Message-ID: <87d09965g3.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 216.205.24.74 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: marcandre.lureau@gmail.com, qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Kevin Wolf writes: > This moves the QMP dispatcher to a coroutine and runs all QMP command > handlers that declare 'coroutine': true in coroutine context so they > can avoid blocking the main loop while doing I/O or waiting for other > events. > > For commands that are not declared safe to run in a coroutine, the > dispatcher drops out of coroutine context by calling the QMP command > handler from a bottom half. > > Signed-off-by: Kevin Wolf Uh, what about @cur_mon? @cur_mon points to the current monitor while a command executes. Initial value is null. It is set in three places (not counting unit tests), and all three save, set, do something that may use @cur_mon, restore: * monitor_qmp_dispatch(), for use within qmp_dispatch() * monitor_read(), for use within handle_hmp_command() * qmp_human_monitor_command(), also for use within handle_hmp_command() Therefore, @cur_mon is null unless we're running within qmp_dispatch() or handle_hmp_command(). Example of use: error_report() & friends print "to current monitor if we have one, else to stderr." Makes sharing code between HMP and CLI easier. Uses @cur_mon under the hood. @cur_mon is thread-local. I'm afraid we have to save, clear and restore @cur_mon around a yield.