Commit 0113d461 authored by Beau Belgrave's avatar Beau Belgrave Committed by Steven Rostedt (Google)
Browse files

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.

Link: https://lkml.kernel.org/r/20230614163336.5797-7-beaub@linux.microsoft.com



Signed-off-by: default avatarBeau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 61701242

Documentation/trace/user_events.rst

+3 −4
Original line number Diff line number Diff line
@@ -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