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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1770823546; 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=AlvWkLh2q9kvkujtvhxT6wWaNJYREeGTNSINBGVu23LwgwA316cLQA1TY+YuSRw5D1UQ9r ogEC/9Dfo07iaR5hQd75LyMgGKEQdO6vg+73Tn/3KveZF+QVLk6GHclddNqyUZF8Mq8pPs hd/Ba8ZLDsEOrBkjq8OhlZOMMiCYD5Y= X-MC-Unique: uSHY1e4TMZiN01Zdm3jaxg-1 X-Mimecast-MFC-AGG-ID: uSHY1e4TMZiN01Zdm3jaxg_1770823539 From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: Manos Pitsidianakis , Stefan Weil , "Dr. David Alan Gilbert" , Pierrick Bouvier , devel@lists.libvirt.org, =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Hanna Reitz , Kevin Wolf , qemu-block@nongnu.org, qemu-rust@nongnu.org, Paolo Bonzini , Markus Armbruster , Gerd Hoffmann , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Christian Schoenebeck , Richard Henderson Subject: [PATCH v6 04/27] monitor: initialize global data from a constructor Date: Wed, 11 Feb 2026 15:24:45 +0000 Message-ID: <20260211152508.732487-5-berrange@redhat.com> In-Reply-To: <20260211152508.732487-1-berrange@redhat.com> References: <20260211152508.732487-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 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: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_H2=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_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: 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: 1770823656920154100 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