tracepoints: format documentation

Impact: documentation update

Properly format Documentation/tracepoints.txt - it was full of
overlong lines and other typographical problems.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

Documentation/tracepoints.txt

@@ -3,28 +3,30 @@
 			    Mathieu Desnoyers
 
 
-This document introduces Linux Kernel Tracepoints and their use. It provides
+This document introduces Linux Kernel Tracepoints and their use. It
-examples of how to insert tracepoints in the kernel and connect probe functions
+provides examples of how to insert tracepoints in the kernel and
-to them and provides some examples of probe functions.
+connect probe functions to them and provides some examples of probe
+functions.
 
 
 * Purpose of tracepoints
 
-A tracepoint placed in code provides a hook to call a function (probe) that you
+A tracepoint placed in code provides a hook to call a function (probe)
-can provide at runtime. A tracepoint can be "on" (a probe is connected to it) or
+that you can provide at runtime. A tracepoint can be "on" (a probe is
-"off" (no probe is attached). When a tracepoint is "off" it has no effect,
+connected to it) or "off" (no probe is attached). When a tracepoint is
-except for adding a tiny time penalty (checking a condition for a branch) and
+"off" it has no effect, except for adding a tiny time penalty
-space penalty (adding a few bytes for the function call at the end of the
+(checking a condition for a branch) and space penalty (adding a few
-instrumented function and adds a data structure in a separate section).  When a
+bytes for the function call at the end of the instrumented function
-tracepoint is "on", the function you provide is called each time the tracepoint
+and adds a data structure in a separate section).  When a tracepoint
-is executed, in the execution context of the caller. When the function provided
+is "on", the function you provide is called each time the tracepoint
-ends its execution, it returns to the caller (continuing from the tracepoint
+is executed, in the execution context of the caller. When the function
-site).
+provided ends its execution, it returns to the caller (continuing from
+the tracepoint site).
 
 You can put tracepoints at important locations in the code. They are
 lightweight hooks that can pass an arbitrary number of parameters,
-which prototypes are described in a tracepoint declaration placed in a header
+which prototypes are described in a tracepoint declaration placed in a
-file.
+header file.
 
 They can be used for tracing and performance accounting.
 
@@ -63,36 +65,41 @@ Where :
 - subsys_eventname is an identifier unique to your event
     - subsys is the name of your subsystem.
     - eventname is the name of the event to trace.
-- TPPTOTO(int firstarg, struct task_struct *p) is the prototype of the function
-  called by this tracepoint.
-- TPARGS(firstarg, p) are the parameters names, same as found in the prototype.
 
-Connecting a function (probe) to a tracepoint is done by providing a probe
+- TPPTOTO(int firstarg, struct task_struct *p) is the prototype of the
-(function to call) for the specific tracepoint through
+  function called by this tracepoint.
+
+- TPARGS(firstarg, p) are the parameters names, same as found in the
+  prototype.
+
+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.
-tracepoint_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_synchronize_unregister() must be called before the end of
-tracepoint, but a single definition must be made of a given tracepoint name over
+the module exit function to make sure there is no caller left using
-all the kernel to make sure no type conflict will occur. Name mangling of the
+the probe. This, and the fact that preemption is disabled around the
-tracepoints is done using the prototypes to make sure typing is correct.
+probe call, make sure that probe removal and module unload are safe.
-Verification of probe type correctness is done at the registration site by the
+See the "Probe example" section below for a sample probe module.
-compiler. Tracepoints can be put in inline functions, inlined static functions,
-and unrolled loops as well as regular functions.
 
-The naming scheme "subsys_event" is suggested here as a convention intended
+The tracepoint mechanism supports inserting multiple instances of the
-to limit collisions. Tracepoint names are global to the kernel: they are
+same tracepoint, but a single definition must be made of a given
-considered as being the same whether they are in the core kernel image or in
+tracepoint name over all the kernel to make sure no type conflict will
-modules.
+occur. Name mangling of the tracepoints is done using the prototypes
+to make sure typing is correct. Verification of probe type correctness
+is done at the registration site by the compiler. Tracepoints can be
+put in inline functions, inlined static functions, and unrolled loops
+as well as regular functions.
+
+The naming scheme "subsys_event" is suggested here as a convention
+intended to limit collisions. Tracepoint names are global to the
+kernel: they are considered as being the same whether they are in the
+core kernel image or in modules.
 
 If the tracepoint has to be used in kernel modules, an
-EXPORT_TRACEPOINT_SYMBOL_GPL() or EXPORT_TRACEPOINT_SYMBOL() can be used to
+EXPORT_TRACEPOINT_SYMBOL_GPL() or EXPORT_TRACEPOINT_SYMBOL() can be
-export the defined tracepoints.
+used to export the defined tracepoints.
 
 * Probe / tracepoint example