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authorRusty Russell <rusty@rustcorp.com.au>2008-12-13 21:55:51 +1030
committerRusty Russell <rusty@rustcorp.com.au>2008-12-13 21:55:51 +1030
commit968ea6d80e395cf11a51143cfa1b9a14ada676df (patch)
treedc2acec8c9bdced33afe1e273ee5e0b0b93d2703 /Documentation/markers.txt
parent7be7585393d311866653564fbcd10a3232773c0b (diff)
parent8299608f140ae321e4eb5d1306184265d2b9511e (diff)
Merge ../linux-2.6-x86
Conflicts: arch/x86/kernel/io_apic.c kernel/sched.c kernel/sched_stats.h
Diffstat (limited to 'Documentation/markers.txt')
-rw-r--r--Documentation/markers.txt29
1 files changed, 24 insertions, 5 deletions
diff --git a/Documentation/markers.txt b/Documentation/markers.txt
index 089f6138fcd..d2b3d0e91b2 100644
--- a/Documentation/markers.txt
+++ b/Documentation/markers.txt
@@ -51,11 +51,16 @@ to call) for the specific marker through marker_probe_register() and can be
activated by calling marker_arm(). Marker deactivation can be done by calling
marker_disarm() as many times as marker_arm() has been called. Removing a probe
is done through marker_probe_unregister(); it will disarm 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.
+
+marker_synchronize_unregister() must be called between probe unregistration and
+the first occurrence of
+- the end of module exit function,
+ to make sure there is no caller left using the probe;
+- the free of any resource used by the probes,
+ to make sure the probes wont be accessing invalid data.
+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 marker mechanism supports inserting multiple instances of the same marker.
Markers can be put in inline functions, inlined static functions, and
@@ -70,6 +75,20 @@ a printk warning which identifies the inconsistency:
"Format mismatch for probe probe_name (format), marker (format)"
+Another way to use markers is to simply define the marker without generating any
+function call to actually call into the marker. This is useful in combination
+with tracepoint probes in a scheme like this :
+
+void probe_tracepoint_name(unsigned int arg1, struct task_struct *tsk);
+
+DEFINE_MARKER_TP(marker_eventname, tracepoint_name, probe_tracepoint_name,
+ "arg1 %u pid %d");
+
+notrace void probe_tracepoint_name(unsigned int arg1, struct task_struct *tsk)
+{
+ struct marker *marker = &GET_MARKER(kernel_irq_entry);
+ /* write data to trace buffers ... */
+}
* Probe / marker example