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Code Issues Releases Wiki Activity

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: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Beau Belgrave 2023-06-14 09:33:36 -07:00 committed by Steven Rostedt (Google)
parent 61701242e8
commit 0113d4615d
1 changed files with 3 additions and 4 deletions
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7
Documentation/trace/user_events.rst
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@ -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