From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8AC37CAC5A0 for ; Sat, 20 Sep 2025 07:07:42 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uzrgP-0004gB-Eb; Sat, 20 Sep 2025 03:06:59 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uzrgL-0004e4-Uw for qemu-devel@nongnu.org; Sat, 20 Sep 2025 03:06:54 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uzrgJ-00060D-Ag for qemu-devel@nongnu.org; Sat, 20 Sep 2025 03:06:53 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758351993; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xVrGGFKgxQBTOyUnsWwqaaL0MGtg4Ks2UExTtILrpII=; b=VFoIhmk5CUgdabbhJQ7HWoFRbKMwH6QkTpIbaPLH3QxYxRrnO8YV96pvTimIr9157YE0O+ 5/sHDkSVrhbo6P8k615TbabFrAKpM+bXY7nDiu6YnPkUI03q8WO90V5fJ1tRm5XsHMA3sf qlhC7V1RNsI00mpiIxzzTUzQWIMUsh0= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-672-VzFDjx8VNI6ULCcNWs0ZMQ-1; Sat, 20 Sep 2025 03:06:29 -0400 X-MC-Unique: VzFDjx8VNI6ULCcNWs0ZMQ-1 X-Mimecast-MFC-AGG-ID: VzFDjx8VNI6ULCcNWs0ZMQ_1758351988 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 89E8F180057D; Sat, 20 Sep 2025 07:06:27 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.45.242.33]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id EADD31955F21; Sat, 20 Sep 2025 07:06:25 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 257DE21E6A27; Sat, 20 Sep 2025 09:06:23 +0200 (CEST) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, Hanna Reitz , Kevin Wolf , =?utf-8?Q?Marc-Andr?= =?utf-8?Q?=C3=A9?= Lureau , Christian Schoenebeck , Richard Henderson , Manos Pitsidianakis , Stefan Weil , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Gerd Hoffmann , Paolo Bonzini , "Dr. David Alan Gilbert" Subject: Re: [PATCH v3 12/20] monitor: introduce monitor_cur_hmp() function In-Reply-To: ("Daniel P. =?utf-8?Q?Berrang?= =?utf-8?Q?=C3=A9=22's?= message of "Fri, 19 Sep 2025 14:29:15 +0100") References: <20250910180357.320297-1-berrange@redhat.com> <20250910180357.320297-13-berrange@redhat.com> <87zfaqwr2a.fsf@pond.sub.org> Date: Sat, 20 Sep 2025 09:06:23 +0200 Message-ID: <87ldm9txg0.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.105, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Daniel P. Berrang=C3=A9 writes: > On Fri, Sep 19, 2025 at 02:43:41PM +0200, Markus Armbruster wrote: >> Daniel P. Berrang=C3=A9 writes: >>=20 >> > A number of callers use monitor_cur() followed by !monitor_cur_is_qmp(= ). >>=20 >> "A number of"? I can see just one: >>=20 >> int error_vprintf(const char *fmt, va_list ap) >> { >> Monitor *cur_mon =3D monitor_cur(); >>=20 >> if (cur_mon && !monitor_cur_is_qmp()) { >> return monitor_vprintf(cur_mon, fmt, ap); >> } >> return vfprintf(stderr, fmt, ap); >> } > > Opps, that'll be referring to the other use of monitor_cur() in my > patches that I then removed when I re-ordered the series. > >>=20 >> > This is undesirable because monitor_cur_is_qmp() will itself call >> > monitor_cur() again, and monitor_cur() must acquire locks and do >> > hash table lookups. Introducing a monitor_cur_hmp() helper will >> > combine the two operations into one reducing cost. I think the actual interface flaw is having monitor_cur_is_qmp(). In master, monitor_cur_is_qmp() is only used in monitor/monitor.c. Both call sites have the value of monitor_cur() available as @cur_mon. They'd be better off calling monitor_is_qmp(cur_mon). Note that in master nothing outside monitor/ cares whether a monitor is QMP or HMP. I like that. Your series doesn't preserve this property. You move the first call site error_vprintf() from monitor/monitor.c to util/error-report.c in PATCH 11. QMP vs. HMP is no longer encapsulated. Slighly irksome. PATCH 13 replaces monitor_cur_is_qmp() by monitor_cur_hmp() there, and PATCH 14 adds a second use. The second call site error_vprintf() gets inlined into ui/vnc.c by PATCH 10. QMP vs. HMP leaks into ui/. Again, only slighly irksome. We could instead preserve the status quo: error_vprintf() stays put in monitor.c, error_printf_unless_qmp() stays around. Independently, I feel we should drop monitor_cur_is_qmp() and not introduce monitor_cur_hmp(). Just use monitor_cur() and monitor_is_qmp(). Move monitor_is_qmp() from monitor-internal.h to monitor.h if it's needed outside the monitor. Have to make it not inline then. >> This made me expect the patch replaces the undesirable uses. It does >> not; the new function remains unused for now. >>=20 >> > Signed-off-by: Daniel P. Berrang=C3=A9 >> > --- >> > include/monitor/monitor.h | 1 + >> > monitor/monitor.c | 14 ++++++++++++++ >> > stubs/monitor-core.c | 5 +++++ >> > tests/unit/test-util-sockets.c | 1 + >> > 4 files changed, 21 insertions(+) >> > >> > diff --git a/include/monitor/monitor.h b/include/monitor/monitor.h >> > index 296690e1f1..c3b79b960a 100644 >> > --- a/include/monitor/monitor.h >> > +++ b/include/monitor/monitor.h >> > @@ -14,6 +14,7 @@ typedef struct MonitorOptions MonitorOptions; >> > extern QemuOptsList qemu_mon_opts; >> >=20=20 >> > Monitor *monitor_cur(void); >> > +Monitor *monitor_cur_hmp(void); >> > Monitor *monitor_set_cur(Coroutine *co, Monitor *mon); >> > bool monitor_cur_is_qmp(void); >> >=20=20 >> > diff --git a/monitor/monitor.c b/monitor/monitor.c >> > index e1e5dbfcbe..cff502c53e 100644 >> > --- a/monitor/monitor.c >> > +++ b/monitor/monitor.c >> > @@ -84,6 +84,20 @@ Monitor *monitor_cur(void) >> > return mon; >> > } >> >=20=20 >> > +Monitor *monitor_cur_hmp(void) >> > +{ >> > + Monitor *mon; >> > + >> > + qemu_mutex_lock(&monitor_lock); >> > + mon =3D g_hash_table_lookup(coroutine_mon, qemu_coroutine_self()); >> > + if (mon && monitor_is_qmp(mon)) { >> > + mon =3D NULL; >> > + } >> > + qemu_mutex_unlock(&monitor_lock); >> > + >> > + return mon; >> > +} >> > + >> > /** >> > * Sets a new current monitor and returns the old one. >> > * >> > diff --git a/stubs/monitor-core.c b/stubs/monitor-core.c >> > index b498a0f1af..1e0b11ec29 100644 >> > --- a/stubs/monitor-core.c >> > +++ b/stubs/monitor-core.c >> > @@ -7,6 +7,11 @@ Monitor *monitor_cur(void) >> > return NULL; >> > } >> >=20=20 >> > +Monitor *monitor_cur_hmp(void) >> > +{ >> > + return NULL; >> > +} >> > + >> > bool monitor_cur_is_qmp(void) >> > { >> > return false; >> > diff --git a/tests/unit/test-util-sockets.c b/tests/unit/test-util-soc= kets.c >> > index bd48731ea2..d40813c682 100644 >> > --- a/tests/unit/test-util-sockets.c >> > +++ b/tests/unit/test-util-sockets.c >> > @@ -72,6 +72,7 @@ int monitor_get_fd(Monitor *mon, const char *fdname,= Error **errp) >> > * otherwise we get duplicate syms at link time. >> > */ >> > Monitor *monitor_cur(void) { return cur_mon; } >> > +Monitor *monitor_cur_hmp(void) { return cur_mon; } >>=20 >> @cur_mon is a fake here. Why do you make this fake monitor HMP? If we >> somehow call error_vprintf(), it'll call monitor_vprintf(), which will >> dereference the fake monitor. Best possible outcome would be an >> immediate crash. > > Current code has 'monitor_cur' return 'cur_mon', and 'monitor_cur_is_qmp' > (below) return 'false'. IOW, the current behaviour of the stubs is that > 'cur_mon' is HMP, so I just maintained those semantics. monitor_cur_is_qmp() below is from your PATCH 11, though. > We've stubbed monitor_vprintf() too so it'll abort() no matter what, as > we don't expect that code path to be triggered from this test suite. Point! Nevermind :) >> > bool monitor_cur_is_qmp(void) { return false; } >> > Monitor *monitor_set_cur(Coroutine *co, Monitor *mon) { abort(); } >> > int monitor_vprintf(Monitor *mon, const char *fmt, va_list ap) { abor= t(); } > > > With regards, > Daniel