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tracing/user_events: Document auto-cleanup and remove dyn_event refs

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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 /sys/kernel/tracing/user_events_status and can both register and write
data out via /sys/kernel/tracing/user_events_data. 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 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 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 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 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. 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 Unregistering
------------- -------------
If after registering an event it is no longer wanted to be updated then it can If after registering an event it is no longer wanted to be updated then it can