From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f181.google.com (mail-pf1-f181.google.com [209.85.210.181]) (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 2C78414037F for ; Mon, 11 Nov 2024 05:51:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731304314; cv=none; b=BFdiRFR1gqZIYRnYL3ZN630Il47QDJxdvRNV7X7/mq9eTnTV5xsQmdSjpaCJM5hYeftugxcwxYpWHXuUrdgp2YK3XA8RxdeIz07Of7b3hrLJYZTfYYl4yMK0+c+/OOslBXdS6NNG04r4DFeRL9H9aADKhCSI/+Nh6iwiilzhRAo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731304314; c=relaxed/simple; bh=YEdfaM3Jd4KS472gYqcc4l9HPKkzSqmWnqgKk628khM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ix4YSoYt1w1aPwCZCKj4toCOO7QQVyNgbrJ4Wp+H9swqa30V/RFOuG9UcuqN6brSOhtrNSrz6ppJLA+ns+MD+rFs72u1zRYx26U+kC2jrxRjyXJklRmhN2f6pwjgCOVyV/rO1QpY5mpLJ0Od7XDbaQcDFwEWZw4D4fsH1eU/J80= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org; spf=pass smtp.mailfrom=chromium.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b=fvneTsgv; arc=none smtp.client-ip=209.85.210.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=chromium.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=chromium.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="fvneTsgv" Received: by mail-pf1-f181.google.com with SMTP id d2e1a72fcca58-71e49ad46b1so3503126b3a.1 for ; Sun, 10 Nov 2024 21:51:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1731304312; x=1731909112; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=Foh0UsYIXPUZmsrbDQnaRrOZh3M/3AkXvl3AtEjmLXE=; b=fvneTsgvZx2nYMaIPhM7Ncf3+q86NLvyXiDlLtEhYr9ih2KpBInRGvZY+NOnv9RcQE zsmNjn+jy/hMPD0VbHK6derUb8cxZlRNIEdwkjisqVQDgZXlM3H3Yz+sfymmlcjlCmhS xYHjuOgNaq0+D6dKUZRynhoiPIUSgpHdTAF9g= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1731304312; x=1731909112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Foh0UsYIXPUZmsrbDQnaRrOZh3M/3AkXvl3AtEjmLXE=; b=Y5xBn/vmjyf5A5bv1V0xWC3NKVPowqBGUjvcqjzrD0xB3cIcvDDQebhVzWzRJ8uQZC hcra4aEpfExSe+TOS8wBv1MqiMxSa+t4IBx1joeUfeKqUoJlfZ0jvYq/QRVOYH7CbDDS zAqLAD6hLaA7AVNfXE/6a1rFs8VpurLcJ2n/fkJp4NKIjyju4SycktZb6pmp9JvKU7p1 ZXoWzI+7DnNRy+gikmVkR54uiLZSvrFCCS8U0hONFfi3U62pEmbHbDRFxhuy1dgCi6GS cddLYyf39FcWH2Kw3LFXaSE+/7xib1iRUne4+TlFCq6CGYt3AfhOWiFZKVFW5hUrdBJy pW1w== X-Gm-Message-State: AOJu0YxCcdN6v7g2cXRJIsUq5sbx81w9wM7GB1AU/xSVOr/xbjDsGMTq J080k6xL3owVcthsdcyI6oNWnfBBb1LMkF1jq6WBKkRv3JrFj+9xFkGFUF2UAg== X-Google-Smtp-Source: AGHT+IF/+AvkwmPA2wuy0MVZEKqJsApzJ/i3RyTv4BlbJnKa2Sv5Pc2joVr+5WcVWSGIEu5T64xndw== X-Received: by 2002:a05:6a00:3a14:b0:71e:6a13:9bac with SMTP id d2e1a72fcca58-7241312915emr17467219b3a.0.1731304312323; Sun, 10 Nov 2024 21:51:52 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:a43c:b34:8b29:4f8]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-724079a4126sm8396292b3a.102.2024.11.10.21.51.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 10 Nov 2024 21:51:51 -0800 (PST) Date: Mon, 11 Nov 2024 14:51:46 +0900 From: Sergey Senozhatsky To: Andrii Nakryiko Cc: bpf@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, adobriyan@gmail.com, shakeel.butt@linux.dev, hannes@cmpxchg.org, ak@linux.intel.com, osandov@osandov.com, song@kernel.org, jannh@google.com, linux-fsdevel@vger.kernel.org, willy@infradead.org, Eduard Zingerman Subject: Re: [PATCH v7 bpf-next 09/10] bpf: wire up sleepable bpf_get_stack() and bpf_get_task_stack() helpers Message-ID: <20241111055146.GA1458936@google.com> References: <20240829174232.3133883-1-andrii@kernel.org> <20240829174232.3133883-10-andrii@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240829174232.3133883-10-andrii@kernel.org> Hi, On (24/08/29 10:42), Andrii Nakryiko wrote: > Now that build ID related internals in kernel/bpf/stackmap.c can be used > both in sleepable and non-sleepable contexts, we need to add additional > rcu_read_lock()/rcu_read_unlock() protection around fetching > perf_callchain_entry, but with the refactoring in previous commit it's > now pretty straightforward. We make sure to do rcu_read_unlock (in > sleepable mode only) right before stack_map_get_build_id_offset() call > which can sleep. By that time we don't have any more use of > perf_callchain_entry. Shouldn't this be backported to stable kernels? It seems that those still do suspicious-RCU deference: __bpf_get_stack() get_perf_callchain() perf_callchain_user() perf_get_guest_cbs()