[patch 15/16] Tracepoints : documentation fix teardown

[Mathieu Desnoyers]

Need a tracepoint_synchronize_unregister() before the end of exit() to make sure
every probe callers have exited the non preemptible section and thus are not
executing the probe code anymore.

Impact: documentation update.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
CC: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
CC: "Frank Ch. Eigler" <fche@xxxxxxxxxx>
CC: Ingo Molnar <mingo@xxxxxxx>
CC: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 Documentation/tracepoints.txt |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

Index: linux-2.6-lttng/Documentation/tracepoints.txt
===================================================================
--- linux-2.6-lttng.orig/Documentation/tracepoints.txt	2008-11-14 17:18:59.000000000 -0500
+++ linux-2.6-lttng/Documentation/tracepoints.txt	2008-11-14 17:19:05.000000000 -0500
@@ -70,10 +70,12 @@ Where :
 Connecting a function (probe) to a tracepoint is done by providing a probe
 (function to call) for the specific tracepoint through
 register_trace_subsys_eventname().  Removing a probe is done through
-unregister_trace_subsys_eventname(); it will remove the probe sure there is no
-caller left using the probe when it returns. Probe removal is preempt-safe
-because preemption is disabled around the probe call. See the "Probe example"
-section below for a sample probe module.
+unregister_trace_subsys_eventname(); it will remove the probe.
+marker_synchronize_unregister() must be called before the end of the module exit
+function to make sure there is no caller left using the probe. This, and the
+fact that preemption is disabled around the probe call, make sure that probe
+removal and module unload are safe. See the "Probe example" section below for a
+sample probe module.
 
 The tracepoint mechanism supports inserting multiple instances of the same
 tracepoint, but a single definition must be made of a given tracepoint name over

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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