From patchwork Wed Feb 14 17:50:46 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Beau Belgrave X-Patchwork-Id: 13556875 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id C25C086644; Wed, 14 Feb 2024 17:50:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707933059; cv=none; b=iEtBrxkauEcGE4/aBoeuZJoDgnXKE5bjOxGHtKvXwWI6bhr3/Z+j47FGHC3iTsxewTKx738ton7zsNQmUPVwGli6/epmdRD/AZaorHtG2EWMaCxz2rj/WJKd1m2pAxsToxy3P8L2I3kwYGOJtcu77w3kPAg8kScqlF/lLlWwfe0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707933059; c=relaxed/simple; bh=1n+POexB4IxIKN4NogGOvLi6IfL+92Wk9tP/cRbJstg=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=tjjRrzwr7f8WjTxKaxv0IEGH6UErVg2QLfZVuY5NoyR4jY+2Eyd18DkEU8mcxyyZa/6M6gBviZP0vJH1YIe+7IlSB0rjLDEeiEft7GqX/NzAOMdEosmYYOnLKTWCVtF39DATXBYo5g2l7N9kROWz+LQtJaFkMZF5l+dP97btDD8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=tGzDrNLn; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="tGzDrNLn" Received: from localhost.localdomain (unknown [4.155.48.117]) by linux.microsoft.com (Postfix) with ESMTPSA id 59AB320B2004; Wed, 14 Feb 2024 09:50:56 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 59AB320B2004 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1707933056; bh=9VOCGDdI8wf7ppg3CttBYebJqIACHcsfFVDg2ERPXoo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tGzDrNLnvdm7wkDwXHHGty2XSx7A6lxBHg7yWMvzCC0UqI+U8U4e2wbJGTtOg3XB/ RyKh3ul3asNW9w2nYqGIo8RnajGdnLV/4H3desJ8oatH+EB4pm/PlXaOW8DHN5EOkq e6pXtt2g9uuDLxBsAmBTsGpD4kImHeeEYObSBQVc= From: Beau Belgrave To: rostedt@goodmis.org, mhiramat@kernel.org Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com Subject: [PATCH v3 4/4] tracing/user_events: Document multi-format flag Date: Wed, 14 Feb 2024 17:50:46 +0000 Message-Id: <20240214175046.240-5-beaub@linux.microsoft.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240214175046.240-1-beaub@linux.microsoft.com> References: <20240214175046.240-1-beaub@linux.microsoft.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User programs can now ask user_events to handle the synchronization of multiple different formats for an event with the same name via the new USER_EVENT_REG_MULTI_FORMAT flag. Add a section for USER_EVENT_REG_MULTI_FORMAT that explains the intended purpose and caveats of using it. Explain how deletion works in these cases and how to use /sys/kernel/tracing/dynamic_events for per-version deletion. Signed-off-by: Beau Belgrave --- Documentation/trace/user_events.rst | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) diff --git a/Documentation/trace/user_events.rst b/Documentation/trace/user_events.rst index d8f12442aaa6..1d5a7626e6a6 100644 --- a/Documentation/trace/user_events.rst +++ b/Documentation/trace/user_events.rst @@ -92,6 +92,24 @@ The following flags are currently supported. process closes or unregisters the event. Requires CAP_PERFMON otherwise -EPERM is returned. ++ USER_EVENT_REG_MULTI_FORMAT: The event can contain multiple formats. This + allows programs to prevent themselves from being blocked when their event + format changes and they wish to use the same name. When this flag is used the + tracepoint name will be in the new format of "name.unique_id" vs the older + format of "name". A tracepoint will be created for each unique pair of name + and format. This means if several processes use the same name and format, + they will use the same tracepoint. If yet another process uses the same name, + but a different format than the other processes, it will use a different + tracepoint with a new unique id. Recording programs need to scan tracefs for + the various different formats of the event name they are interested in + recording. The system name of the tracepoint will also use "user_events_multi" + instead of "user_events". This prevents single-format event names conflicting + with any multi-format event names within tracefs. The unique_id is output as + a hex string. Recording programs should ensure the tracepoint name starts with + the event name they registered and has a suffix that starts with . and only + has hex characters. For example to find all versions of the event "test" you + can use the regex "^test\.[0-9a-fA-F]+$". + Upon successful registration the following is set. + write_index: The index to use for this file descriptor that represents this @@ -106,6 +124,9 @@ or perf record -e user_events:[name] when attaching/recording. **NOTE:** The event subsystem name by default is "user_events". Callers should not assume it will always be "user_events". Operators reserve the right in the future to change the subsystem name per-process to accommodate event isolation. +In addition if the USER_EVENT_REG_MULTI_FORMAT flag is used the tracepoint name +will have a unique id appended to it and the system name will be +"user_events_multi" as described above. Command Format ^^^^^^^^^^^^^^ @@ -156,7 +177,11 @@ to request deletes than the one used for registration due to this. to the event. If programs do not want auto-delete, they must use the USER_EVENT_REG_PERSIST flag when registering the event. Once that flag is used the event exists until DIAG_IOCSDEL is invoked. Both register and delete of an -event that persists requires CAP_PERFMON, otherwise -EPERM is returned. +event that persists requires CAP_PERFMON, otherwise -EPERM is returned. When +there are multiple formats of the same event name, all events with the same +name will be attempted to be deleted. If only a specific version is wanted to +be deleted then the /sys/kernel/tracing/dynamic_events file should be used for +that specific format of the event. Unregistering -------------