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([38.41.223.211]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b26eaf8e05fsm172370a12.39.2025.05.15.10.46.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 May 2025 10:46:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1747331207; x=1747936007; darn=nongnu.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=rVsacexuhDTK9h99dudm/8TY6NWVjrdnKMHqsB0i42Y=; b=i+7WG0pPC744b8+dGfj4xN+sRj18wcHeTFCmHXnTvZ+HZIqr4Uz4UFOCywiISldzZJ +08SS6yBK+kGgcIfF8w/TIm06cwYCB017Vms1HdeCoktLHDtDMH/owVaBc8+LS3hEv1N oP8Y5foLU3cN/bFZlzYoH+oSHLMJb5V6/CHwSFylImzovcd3SfVtjcQrLGd86jt0T1Ja BsBSay5Pw1Qe88rFZd3zDyk0Lb+herXRa6XRgDI9f8qqeTvbBGVdUB7PDB2gDleUmwct gx3VjtsKm8qfK0zyhc7uCNmDrrgcT7aRSYmhA0iJzYnfCzDjB5qA60AcDnkg6i8bEVRY idSw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747331207; x=1747936007; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=rVsacexuhDTK9h99dudm/8TY6NWVjrdnKMHqsB0i42Y=; b=kvU0/iuaKGEzjaHvIMQAgLd93HbbMKKGhYQwBjcjOrmkTdNwIHMvABkUWStX9HkfQj Vp9fZebzBdt7N8rzAJlHvcjw0GhoCrHnKappU6Exs23HZ8L6DHFSPqrDVTmiGQBNsbAB lZzB+coCBhGCdeyTg/RNtnaJdPTAWcBMR5iFeuIGvcPritzua+fHn+1bVdAbJG3Kovii XaLp1g6kGOE61Mfy45Cj3ujtP++GrXuVM6KnFeTgnK8xLUh3to280JBs0TAyEAcsfkNn ulrpbEm9KNp1BGQQNZQ+qEyxsMBqAOQJKSNYGJOo1UazgOnXsNtJJFsbse7lEhNksCFK jFSQ== X-Gm-Message-State: AOJu0Yx4v2+3hgsNrdU7LYZBFrjs9xMSYGVRxYK2dhQk5bbvfWTsJHTQ 1D39pcLoB6ol91m34Kwem96wI5CyaI9uMk4orytohc8qqflpCERA+B0miOpu7TgOVYmkDE8nqXk H0g6v X-Gm-Gg: ASbGncufhjlnfWaHbLXEKMNOWIf2rkEaBUqbk3HTIIFANdwcKR6/3cwFXbA8EFaYNGJ ippkhHvLV8kFZautO2b4YrSKWlwceBBWoBR/W3notZdFUhHi1hOokakqqYIkKCQy5RetVmEOYBp G3qM0OBQT1gSuPYjpRWVJv8AAvwv2QT1rj58Exn/J6vCZqUP4IVr0tBtIGWbhxwlvf3n0rYe55A 2MOvIR+QDQG7exdjsfGR5d8a8dsX7cDa2XY4lb2I044eXOrWJbfW7GsBczYFoakNLjEkJvcS2pP /L5pBJgh+m9aGCvzBEBEFE+LQRkU15D+z1mLOpDruB2hBrDYLY8= X-Google-Smtp-Source: AGHT+IEAYa2bH9UaWLLfI4vADebdaLPcMS2f4ELCGRWN3SnZr75CjPCYFWxaR9waE0NhVC1Ftu6C0g== X-Received: by 2002:a05:6a00:856:b0:73f:ff25:90b3 with SMTP id d2e1a72fcca58-742a98b7f48mr367356b3a.24.1747331206980; Thu, 15 May 2025 10:46:46 -0700 (PDT) From: Pierrick Bouvier To: qemu-devel@nongnu.org Cc: qemu-trivial@nongnu.org, npiggin@gmail.com, Paolo Bonzini , Pierrick Bouvier Subject: [PATCH] system/main: comment lock rationale Date: Thu, 15 May 2025 10:46:41 -0700 Message-ID: <20250515174641.4000309-1-pierrick.bouvier@linaro.org> X-Mailer: git-send-email 2.47.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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=2607:f8b0:4864:20::42b; envelope-from=pierrick.bouvier@linaro.org; helo=mail-pf1-x42b.google.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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @linaro.org) X-ZM-MESSAGEID: 1747331279310116600 Content-Type: text/plain; charset="utf-8" Signed-off-by: Pierrick Bouvier Reviewed-by: Richard Henderson --- system/main.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/system/main.c b/system/main.c index 1c022067349..b8f7157cc34 100644 --- a/system/main.c +++ b/system/main.c @@ -69,8 +69,21 @@ int (*qemu_main)(void) =3D os_darwin_cfrunloop_main; int main(int argc, char **argv) { qemu_init(argc, argv); + + /* + * qemu_init acquires the BQL and replay mutex lock. BQL is acquired w= hen + * initializing cpus, to block associated threads until initialization= is + * complete. Replay_mutex lock is acquired on initialization, because = it + * must be held when configuring icount_mode. + * + * On MacOS, qemu main event loop runs in a background thread, as main + * thread must be reserved for UI. Thus, we need to transfer lock owne= rship, + * and the simplest way to do that is to release them, and reacquire t= hem + * from qemu_default_main. + */ bql_unlock(); replay_mutex_unlock(); + if (qemu_main) { QemuThread main_loop_thread; qemu_thread_create(&main_loop_thread, "qemu_main", --=20 2.47.2