From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj2-f13.google.com (mail-pj2-f13.google.com [74.125.227.141]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0E2D73A382B for ; Sat, 26 Sep 2026 08:29:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.227.141 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790411357; cv=none; b=YwxQt4NiZoQvJ6zafpjsIJVTGm6Vjvp0QNCE0IyMFt0ezDGXL4fr81IXUturfm8UXuiXLq9z8h6DIXV68yEt6bKiXuNEmfgYX95CCi+W+NUK/jP67J3X4CtNNiGMCjAQQJ74MTLpGkMYIvdwle/4CCRGpGmK5ojwkCvLTLo2mZs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790411357; c=relaxed/simple; bh=iXM6dXLVZyc4/2LLEhMvfVIyG+SHsbmujZvmS7fw1aA=; h=Content-Type:Date:Message-Id:From:To:Cc:Subject:In-Reply-To: References:MIME-Version; b=Imp5tjLc+w27YzvUUurFqeiQhVNxN8hnpMbJMaiRrnRn2ddABh9GlFk84aUpO45NoMUFbziI0pgnoY2jUu08KwT1k8E1M630K50cJErKqc+jUlvg6ko6Ar+Ciq8tRCu2qWLbt1ipe9zgFaHqVNULPFuMuejpDFuAnrPZob8pUv8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=L1tf1epb; arc=none smtp.client-ip=74.125.227.141 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="L1tf1epb" Received: by mail-pj2-f13.google.com with SMTP id 98e67ed59e1d1-396ccb652d7so1064201a91.0 for ; Sat, 26 Sep 2026 01:29:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1790411355; x=1791016155; darn=vger.kernel.org; h=mime-version:content-transfer-encoding:references:in-reply-to :subject:cc:to:from:message-id:date:content-type:from:to:cc:subject :date:message-id:reply-to:content-type; bh=vsTzuV1eSC7imODMsDAQHQQbWFGBD/RBt6ggI0+EwhA=; b=L1tf1epbkhLphZ2Julis/OkRu7jj8hETfwJ/ktaJBK1t/FnSaBM+B/Cvk8BtSprulN LiTnhae7M11zRQ6WNQLA4WD/vdDuj9nRTm6pOICKA34Y+2mvG7lEMPdf/57cRfUjmJX6 P2rasuRcLzwNc44BxJt5lq3cNRMHqcft+eB5yHVdTfE7PNWyZGhs+3HMjk3kIg6caRpT TGpyYMVH9ya+B8q+vDF7MM77tQM3OGKVyRiQA+4au42hbq6b0SM1/zlrAQ79jDv9k19r Vbp/FjUWRznjhLnpVPM25BQ9x8aTAA+8zE8wL6H5I/RceUNK4KJzisdkbOMQL49P0+7b o8tg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790411355; x=1791016155; h=mime-version:content-transfer-encoding:references:in-reply-to :subject:cc:to:from:message-id:date:content-type:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=vsTzuV1eSC7imODMsDAQHQQbWFGBD/RBt6ggI0+EwhA=; b=0bthOJvBn3UJM7A2IUzQ35muaF/DW7cGTVOVVR7RFY+BLtq5++4T/0nr2MAlNI8OLb 12Ay4wmt8kIBeWzuhllf13D7X6Km1dOw+/4KXjSOebjjaLAfdeT1fEK9QAhqWqlWE6qK fByVBlG5vLiAUCmNytP4IDDu+IX9JqdQGYjMhYu1mWYSUH/w1j43dgmIpmynu6FuYuX+ NMoD7mf5bhKvs0VrMESgsO0hsU3w238p0iu6BB6XUkj3nGhTtlSc+2zq6zSOATZp/rur FkqwdyX5ciQAKTPLAgEZ3cy9GLSjoGuEb5sR0VmzNggIOSs80E+nZiM+ifxL/TlQ1JMO IyAQ== X-Forwarded-Encrypted: i=1; AKwUvByrR/lA33T/avZqiazmBMRKlXUgA8Gm2GrufD56G9hix07HwlXEoapKjvXMReSXT+JAvT45bB+xtYAH15TU6Q==@vger.kernel.org X-Gm-Message-State: AFq9FYKDV7tEzVzTdMjru6qld/7a707HtHIyNnrWQIBoHGnbOvDc2DeB Lf30GWWZztI9Gf8dzAbAh90+aF5qhjZRL+q32Mrj/r/+Tu3WiPsAujwf X-Gm-Gg: AYBFou0e44s5MrDONAkN61zpyDH37xCV1+i3iB8WnasR05wsbLBOY+VYW8r1R/rWGXn 457KwFiTbNAtqjelhLTq9OzLTmPEd1rjjQRD6aIX4sUksJL1E2NGlk0xdMLs+K0wffZ6RKAv84Y TJSaXRN6kj3yXwJ+zmy7dNWMLLzv8Gg3RU/8/0s63YvKViw+LDwpFGIV2fi710OIfVnsfp8HZBG Za0ZrLPHxS3x3ztJiRu2vE4mpoer0qqkpAIdr40FGLLo1XKooaKck6LWJA0hmvLSImPPHmACLJQ 2zOSopGnoRYQ7mMOgFI2bU6ZdjPpykm/44XXVUwjZL0YSQnPfXYV82CK8M3fX88g65Anmr7cDgK tB8OhgYmT+4MJ1KXusH0RgcRd7cpxK12GNROuba+cEel5HMeWsMdfNIznGy/LgQRw4oOjgYWL/x JswSnwDejRa7DxPhjfNqFMz//wHA2u5HgqD0S8UhweHuNVM8idwSOKUQTVoE0RWuKlGj8olvdzg iJZbtkdAe5gVcUKkdH8PkvaiRFEO5+CDGcgRk9Gh3diV4xHRylGwtqaM03cXtHfsce/Ygj9CSrU RBHS X-Received: by 2002:a17:90b:51c1:b0:39e:1692:34bc with SMTP id 98e67ed59e1d1-3a098ad4cd1mr6277315a91.1.1790411355026; Sat, 26 Sep 2026 01:29:15 -0700 (PDT) Received: from localhost ([153.61.198.251]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a0b99e5220sm8692077a91.16.2026.09.26.01.29.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 26 Sep 2026 01:29:13 -0700 (PDT) Content-Type: text/plain; charset=UTF-8 Date: Sat, 26 Sep 2026 08:29:12 +0000 Message-Id: From: "Alexei Starovoitov" To: "Jay Wang" , , "Daniel Borkmann" , "Andrii Nakryiko" , "Eduard Zingerman" , "Kumar Kartikeya Dwivedi" Cc: "Alan Maguire" , "Martin KaFai Lau" , "Yonghong Song" , "Jiri Olsa" , "Nathan Chancellor" , "Nicolas Schier" , , "Luis Chamberlain" , "Petr Pavlu" , "Sami Tolvanen" , , "Miguel Ojeda" , , "Arnd Bergmann" , , "Hazem Mohamed Abuelfotoh" , "Bjoern Doebel" , "Martin Pohlack" , Subject: Re: [PATCH bpf-next v3 4/9] bpf: take the vmlinux BTF from the btf_vmlinux module In-Reply-To: <20260925224229.1850-5-wanjay@amazon.com> References: <20260925224229.1850-1-wanjay@amazon.com> <20260925224229.1850-5-wanjay@amazon.com> X-Mailer: mkdraft (claude review draft; edit before sending) Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, Sep 25, 2026 at 10:42 PM Jay Wang wrote: > + if (!data && load) { > + /* > + * The module notifier installs the BTF before init_module() > + * returns, so it is either there after this or the module is > + * not available (yet). Not cached: a later call retries, > + * e.g. once the module becomes reachable on the root fs. > + */ > + request_module("btf_vmlinux"); This will deadlock. event_btf_ids_read() calls btf_get_module_btf(NULL) with event_mutex held. With =m and BTF not loaded yet cat /sys/kernel/tracing/events/sched/sched_switch/btf_ids gets here and waits for modprobe. modprobe gets to trace_module_notify() which takes event_mutex. lockdep doesn't see it. print_function_args() gets here for every line of the trace, from ftrace_dump() with irqs off too. When the module is not installed that is one modprobe per line. Every caller of bpf_get_btf_vmlinux() and bpf_find_btf_id() was written for a function that doesn't wait for user space. pw-bot: cr