linux-kernel - [PATCH v3 6/6] tracing/user_events: Document auto-cleanup and remove dyn

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Message-Id: <20230614163336.5797-7-beaub@linux.microsoft.com>
Date:   Wed, 14 Jun 2023 09:33:36 -0700
From:   Beau Belgrave <beaub@...ux.microsoft.com>
To:     rostedt@...dmis.org, mhiramat@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        ast@...nel.org, dcook@...ux.microsoft.com
Subject: [PATCH v3 6/6] tracing/user_events: Document auto-cleanup and remove dyn_event refs

Now user_events auto-cleanup upon the last reference by default. This
makes it not possible to use the dynamics event file via tracefs.

Document that auto-cleanup is enabled by default and remove the refernce
to /sys/kernel/tracing/dynamic_events file to make this clear.

Signed-off-by: Beau Belgrave <beaub@...ux.microsoft.com>
---
 Documentation/trace/user_events.rst | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/Documentation/trace/user_events.rst b/Documentation/trace/user_events.rst
index f79987e16cf4..e7b07313550a 100644
--- a/Documentation/trace/user_events.rst
+++ b/Documentation/trace/user_events.rst
@@ -14,10 +14,6 @@ Programs can view status of the events via
 /sys/kernel/tracing/user_events_status and can both register and write
 data out via /sys/kernel/tracing/user_events_data.
 
-Programs can also use /sys/kernel/tracing/dynamic_events to register and
-delete user based events via the u: prefix. The format of the command to
-dynamic_events is the same as the ioctl with the u: prefix applied.
-
 Typically programs will register a set of events that they wish to expose to
 tools that can read trace_events (such as ftrace and perf). The registration
 process tells the kernel which address and bit to reflect if any tool has
@@ -144,6 +140,9 @@ its name. Delete will only succeed if there are no references left to the
 event (in both user and kernel space). User programs should use a separate file
 to request deletes than the one used for registration due to this.
 
+**NOTE:** By default events will auto-delete when there are no references left
+to the event. Flags in the future may change this logic.
+
 Unregistering
 -------------
 If after registering an event it is no longer wanted to be updated then it can
-- 
2.25.1