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 1D37DCAC5A0 for ; Sat, 20 Sep 2025 11:55:48 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uzwBE-0002RE-Nr; Sat, 20 Sep 2025 07:55:05 -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 1uzwB4-0002Qn-AT; Sat, 20 Sep 2025 07:54:55 -0400 Received: from mx.treblig.org ([2a00:1098:5b::1]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uzwB1-0001Lq-W2; Sat, 20 Sep 2025 07:54:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=treblig.org ; s=bytemarkmx; h=Content-Type:MIME-Version:Message-ID:Subject:From:Date:From :Subject; bh=j8oX7mOlUQucL1r/ErQ+BdaybDE6MMjmvLB3+widkis=; b=H2jvEiZkeulkgcgU jNcgwy+3rSBjDO02ydkDgXLwQ/jNXd9bUGcio7O0W4HU7JJS0ZWevl1tb6hGFuS/maw+mGL4DQmeK 1jjh5R/0CVyTXgaTb4OWfC0Q8NnCxKvdcRQu4scYPxVt8G6E26ci1DW6LcWDHn6VllJXhdcy4xOD3 j7wG5lexY+QCJwouwuZnkq+HlQQivXN6ah5xQ1nplFfCGJuoSurYZUL8v7sgX+8HCEZNAhv+hbZlf jkbkYN/ARZQWc6DAuMzTKd9/8nnl5sxc072ZcmYdpuNfhaeWdz5hG9A2A5rkFGr/5Y4mL4uQ1iW6o mdbwo99TJhtMIqWfGA==; Received: from dg by mx.treblig.org with local (Exim 4.96) (envelope-from ) id 1uzwAx-00CHSs-2U; Sat, 20 Sep 2025 11:54:47 +0000 Date: Sat, 20 Sep 2025 11:54:47 +0000 From: "Dr. David Alan Gilbert" To: Markus Armbruster Cc: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , qemu-devel@nongnu.org, qemu-block@nongnu.org, Hanna Reitz , Kevin Wolf , =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , Christian Schoenebeck , Richard Henderson , Manos Pitsidianakis , Stefan Weil , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Gerd Hoffmann , Paolo Bonzini Subject: Re: [PATCH v3 12/20] monitor: introduce monitor_cur_hmp() function Message-ID: References: <20250910180357.320297-1-berrange@redhat.com> <20250910180357.320297-13-berrange@redhat.com> <87zfaqwr2a.fsf@pond.sub.org> <87ldm9txg0.fsf@pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87ldm9txg0.fsf@pond.sub.org> X-Chocolate: 70 percent or better cocoa solids preferably X-Operating-System: Linux/6.1.0-34-amd64 (x86_64) X-Uptime: 11:52:27 up 145 days, 20:06, 1 user, load average: 0.06, 0.02, 0.00 User-Agent: Mutt/2.2.12 (2023-09-09) Received-SPF: pass client-ip=2a00:1098:5b::1; envelope-from=dg@treblig.org; helo=mx.treblig.org X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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 * Markus Armbruster (armbru@redhat.com) wrote: > Daniel P. Berrangé writes: > > > On Fri, Sep 19, 2025 at 02:43:41PM +0200, Markus Armbruster wrote: > >> Daniel P. Berrangé writes: > >> > >> > A number of callers use monitor_cur() followed by !monitor_cur_is_qmp(). > >> > >> "A number of"? I can see just one: > >> > >> int error_vprintf(const char *fmt, va_list ap) > >> { > >> Monitor *cur_mon = monitor_cur(); > >> > >> 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. > > > >> > >> > 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. How about a slightly simpler approach, looking above we have: > >> if (cur_mon && !monitor_cur_is_qmp()) { > >> return monitor_vprintf(cur_mon, fmt, ap); > >> } > >> return vfprintf(stderr, fmt, ap); I think we could replace this with: ret = monitor_vprintf(cur_mon, fmt, ap); if (ret == -1) { ret = vfprintf(stderr, fmt, ap); } return ret; monitor_vprintf already -1 exits if !mon or monitor_is_qmp(mon) Keeps the encapsulation, and is now 'print via the monitor but if it can't do it, use printf' Dave > 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. > >> > >> > Signed-off-by: Daniel P. Berrangé > >> > --- > >> > 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; > >> > > >> > Monitor *monitor_cur(void); > >> > +Monitor *monitor_cur_hmp(void); > >> > Monitor *monitor_set_cur(Coroutine *co, Monitor *mon); > >> > bool monitor_cur_is_qmp(void); > >> > > >> > 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; > >> > } > >> > > >> > +Monitor *monitor_cur_hmp(void) > >> > +{ > >> > + Monitor *mon; > >> > + > >> > + qemu_mutex_lock(&monitor_lock); > >> > + mon = g_hash_table_lookup(coroutine_mon, qemu_coroutine_self()); > >> > + if (mon && monitor_is_qmp(mon)) { > >> > + mon = 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; > >> > } > >> > > >> > +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-sockets.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; } > >> > >> @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) { abort(); } > > > > > > With regards, > > Daniel > -- -----Open up your eyes, open up your mind, open up your code ------- / Dr. David Alan Gilbert | Running GNU/Linux | Happy \ \ dave @ treblig.org | | In Hex / \ _________________________|_____ http://www.treblig.org |_______/