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 688B4C3ABB2 for ; Wed, 28 May 2025 08:14:53 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uKBvk-0007w7-EK; Wed, 28 May 2025 04:14:33 -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 1uKBvb-0007u2-Po for qemu-devel@nongnu.org; Wed, 28 May 2025 04:14:24 -0400 Received: from mail-wm1-x32c.google.com ([2a00:1450:4864:20::32c]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1uKBvY-0005Cw-OS for qemu-devel@nongnu.org; Wed, 28 May 2025 04:14:23 -0400 Received: by mail-wm1-x32c.google.com with SMTP id 5b1f17b1804b1-44b1f5b917fso25867515e9.3 for ; Wed, 28 May 2025 01:14:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1748420055; x=1749024855; darn=nongnu.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=azdm+UxBkdRxIzgKmwhwW+GH3cYuHoEtpkJtFbR5x4c=; b=eCDfRk0jEnnEzUB7olLHyzPhQw7xnrF6qgBuqWmx397UMcnMYVHLelgYnyqVBfpKAh bHiHCoA8kgUotg3MJY8LLQm2pY1iZ93BZfRCupjLTqh/BIp5n7B2N1yJKqVMaAqgzFe6 5igG37QxY6e5QxgcrIGYeTWXIIEG4Zym97xIavlPh3VFBp55+OMQCbnXE+wy8Z3n9tNw lROmHISvKVHQpBlajbCSSWBLqRflfJmw2/0J6DZUAJdO1N4GCPL3uYgEnzA+SJLqzNmR 8D9j0gwNxCgsbn8zOpijqGJsw+SShCBKY7I6mEPs8gYx64wU+yc/lFzV6pAf9Ob8TAyb DyaQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1748420055; x=1749024855; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=azdm+UxBkdRxIzgKmwhwW+GH3cYuHoEtpkJtFbR5x4c=; b=cs586kZNrNCi9O9NCUZUP62tZzxr4hCTBmk1spf4pv1r3GBnRU3nGvHOjehlw7luew BzgNxz1g2IgQUc+6njnAyk8RNuI/AxXqgHJrISJWRh+jXMakZga4VrjNiXevbdh+Ru9L L7BJIIrSMQBqNaiRLiR6dI6T19aiCa1jb50q2TnbdFLL8QHgIN99stL+1CFhDCU6rIid Rav7+8yQG/jWfzn7F2F8YP8YPW8JbNMvU+M0GAstK/Qh5ICNZe6o8Gyz7uX4+3xmTNKW V9cJPb+isBx8ocdwuNMiqKy0kqe8l6mrrchtvzxl4PswAaoJ7fwP5sIheoUedzqcUgj8 vYwg== X-Gm-Message-State: AOJu0Yx1JCv4hWRw1u2+K6b1eg+MHA7z3YUgs1zGJsqKJMYp1nkg6seg TK/OyNg/vIpJ5zlflMLteO4BH5Y/Rp2dnzfXhV+7fDwMXtRwdCjFSYHY1010go+TXhX12l0n04P +9awBgWdOAQ== X-Gm-Gg: ASbGnctvS5KU8FV7T3/kTPRgQOLUk8+XQddn0O1IkF23GJNbYRi4Fsmv6W7Jyw1LLef HviPMjKySd6pDYE+NvGUn+6M4xPd+ZaR05GHrQa3uC1KWJqn0wqE2vgN2KlD46R7Z22J7F3VNu9 nm9vD7U6Zl/bqNOjfaRghvbXRrMjgqHN1z0Oa0VxH+RDdqeUzfnRZOrlfnErLj1G3Cw/6xG2hpK WHWoNbI078lTBkeO6sS9r/FVjXq8naCeHengfhDUOSn+Rmzic/dID6aq7TKUAXhdRkqmhg9LKBg RykxTTs/vdoHny3RX9ZWcZDITyk1x5NE1/RRho4ggbSI884sEDXIjp34 X-Google-Smtp-Source: AGHT+IEitChxRskBOpckNlAeKZTGyH6lERsUE1B1sRmN0bJZFD/naYVMvVwy1aaSn5ZrBZHr38cAIw== X-Received: by 2002:a05:600c:6308:b0:43d:2313:7b4a with SMTP id 5b1f17b1804b1-44c9141ac4emr179687875e9.3.1748420055508; Wed, 28 May 2025 01:14:15 -0700 (PDT) Received: from stoup.. ([195.53.115.74]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4500e1d85b5sm13178645e9.32.2025.05.28.01.14.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 May 2025 01:14:14 -0700 (PDT) From: Richard Henderson To: qemu-devel@nongnu.org Cc: Pierrick Bouvier Subject: [PULL 02/28] system/main: comment lock rationale Date: Wed, 28 May 2025 09:13:44 +0100 Message-ID: <20250528081410.157251-3-richard.henderson@linaro.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250528081410.157251-1-richard.henderson@linaro.org> References: <20250528081410.157251-1-richard.henderson@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::32c; envelope-from=richard.henderson@linaro.org; helo=mail-wm1-x32c.google.com X-Spam_score_int: -1 X-Spam_score: -0.2 X-Spam_bar: / X-Spam_report: (-0.2 / 5.0 requ) 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=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 From: Pierrick Bouvier Signed-off-by: Pierrick Bouvier Reviewed-by: Richard Henderson Signed-off-by: Richard Henderson Message-ID: <20250515174641.4000309-1-pierrick.bouvier@linaro.org> --- system/main.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/system/main.c b/system/main.c index 1c02206734..b8f7157cc3 100644 --- a/system/main.c +++ b/system/main.c @@ -69,8 +69,21 @@ int (*qemu_main)(void) = 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 when + * 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 ownership, + * and the simplest way to do that is to release them, and reacquire them + * from qemu_default_main. + */ bql_unlock(); replay_mutex_unlock(); + if (qemu_main) { QemuThread main_loop_thread; qemu_thread_create(&main_loop_thread, "qemu_main", -- 2.43.0