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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1772732921; 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=kAnXty8ojb0QvYCAJwvtMMolNwPYeQ0lJZK1O5DK5TM=; b=if8GqEtCi1IDHNKTJxhV4tR3ZyKeXaawpg+3f8Os0n1VvNXYF1ytQF1UzjSWrPwQOLkCMk 6Q9SBBZHhFYniRO9Ib68en9RuXx6U61hD6nFt6ljVKnQ1Lsc168KsaCMilfmNelDQGXkTH yGgDuCAobwDRcmOuKlvkzffr+Ue0cIg= X-MC-Unique: V4wl-JcLOeGaH4fxp9c7fw-1 X-Mimecast-MFC-AGG-ID: V4wl-JcLOeGaH4fxp9c7fw_1772732916 From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: Markus Armbruster , Richard Henderson , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , devel@lists.libvirt.org, qemu-rust@nongnu.org, "Dr. David Alan Gilbert" , Gerd Hoffmann , Christian Schoenebeck , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Manos Pitsidianakis , Eduardo Habkost , Pierrick Bouvier , Paolo Bonzini , Stefan Weil Subject: [PULL 08/27] monitor: initialize global data from a constructor Date: Thu, 5 Mar 2026 17:47:24 +0000 Message-ID: <20260305174743.3084606-9-berrange@redhat.com> In-Reply-To: <20260305174743.3084606-1-berrange@redhat.com> References: <20260305174743.3084606-1-berrange@redhat.com> 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 (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -5 X-Spam_score: -0.6 X-Spam_bar: / X-Spam_report: (-0.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_RPBL_BLOCKED=0.892, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.622, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1772732971718158500 Some monitor functions, most notably, monitor_cur() rely on global data being initialized by 'monitor_init_globals()'. The latter is called relatively late in startup. If code triggers error_report() before monitor_init_globals() is called, QEMU will abort when accessing the uninitialized monitor mutex. The critical monitor global data must be initialized from a constructor function, to improve the guarantee that it is done before any possible calls to monitor_cur(). Not only that, but the constructor must be marked to run before the default constructor in case any of them trigger error reporting. Note in particular that the RCU constructor will spawn a background thread so we might even have non-constructor QEMU code running concurrently with other constructors. As a general note, constructors should be extrememly careful about what QEMU code they invoke, as it cannot be guaranteed that the process is fully initialized and so not all normal QEMU API rules apply. Reviewed-by: Richard Henderson Reviewed-by: Dr. David Alan Gilbert Reviewed-by: Markus Armbruster Fixes: e69ee454b5f9 (monitor: Make current monitor a per-coroutine property) Signed-off-by: Daniel P. Berrang=C3=A9 --- monitor/monitor.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/monitor/monitor.c b/monitor/monitor.c index 1273eb7260..dd2c45ded0 100644 --- a/monitor/monitor.c +++ b/monitor/monitor.c @@ -708,18 +708,22 @@ void monitor_cleanup(void) } } =20 -static void monitor_qapi_event_init(void) +/* + * Initialize static vars that have no deps on external + * module initialization, and are required for external + * functions to call things like monitor_cur() + */ +static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY))) +monitor_init_static(void) { + qemu_mutex_init(&monitor_lock); + coroutine_mon =3D g_hash_table_new(NULL, NULL); monitor_qapi_event_state =3D g_hash_table_new(qapi_event_throttle_hash, qapi_event_throttle_equal); } =20 void monitor_init_globals(void) { - monitor_qapi_event_init(); - qemu_mutex_init(&monitor_lock); - coroutine_mon =3D g_hash_table_new(NULL, NULL); - /* * The dispatcher BH must run in the main loop thread, since we * have commands assuming that context. It would be nice to get --=20 2.53.0