Imported linux-2.6.27.39 suse/xen patches.

[ipfire-2.x.git] / src / patches / suse-2.6.27.39 / patches.trace / tracepoints-documentation-fix-teardown.patch

From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Subject: Tracepoints : documentation fix teardown

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.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: Rusty Russell <rusty@rustcorp.com.au>
CC: "Frank Ch. Eigler" <fche@redhat.com>
CC: Ingo Molnar <mingo@elte.hu>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Jan Blunck <jblunck@suse.de>
---
 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	2008-07-31 09:22:56.000000000 -0400
+++ linux-2.6-lttng/Documentation/tracepoints.txt	2008-07-31 09:24:54.000000000 -0400
@@ -68,10 +68,12 @@ 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