From: "Scott Preece" <sepreece@gmail.com>
To: "Mathieu Desnoyers" <mathieu.desnoyers@polymtl.ca>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
hch@infradead.org
Subject: Re: [patch 07/10] Linux Kernel Markers - Documentation
Date: Thu, 10 May 2007 10:51:46 -0500 [thread overview]
Message-ID: <7b69d1470705100851v26e22fedw2b2247c5cae2e783@mail.gmail.com> (raw)
In-Reply-To: <20070510020917.172554217@polymtl.ca>
Hi,
Here is a patch to marker.txt to make the English read a little
better. I didn't change the references to out-of-tree packages.
@@ -3,33 +3,30 @@
Mathieu Desnoyers
- This document introduces to markers and discusses its purpose. It
-shows some usage examples of the Linux Kernel Markers : how to insert markers
-within the kernel and how to connect probes to a marker. Finally, it has some
-probe module examples. This is what connects to a marker.
-
+This document introduces Linux Kernel Markers and their use. It provides
+examples of how to insert markers in the kernel and connect probe functions to
+them and provides some examples of probe functions.
* Purpose of markers
-A marker placed in your code provides a hook to a function (probe) that
+A marker placed in your code provides a hook to call a function (probe) that
you can provide at runtime. A marker can be "on" (a probe is connected to it)
-or "off" (no probe is attached). An "off" marker has no effect. When turned on,
-the function you provide is called each time the marker is executed in the
-execution context of the caller. When the function provided ends its execution,
-it returns to the caller (marker site).
+or "off" (no probe is attached). When a marker is "off" it has no
+effect. When a marker is "on", the function you provide is called each
+time the marker is executed, in the execution context of the
+caller. When the function provided ends its execution, it returns to the
+caller (continuing from the marker site).
-You can put markers at important locations in the code. They act as
+You can put markers at important locations in the code. Markers are
lightweight hooks that can pass an arbitrary number of parameters,
-described in a printk-like format string, to a function whenever the marker
-code is reached.
+described in a printk-like format string, to the attached probe function.
-They can be used for tracing (LTTng, LKET over SystemTAP), overall performance
-accounting (SystemTAP). They could also be used to implement
-efficient hooks for SELinux or any other subsystem that would have this
-kind of need.
+Markers can be used for tracing (LTTng, LKET over SystemTAP), overall
+performance accounting (SystemTAP), or to hook to monitoring
+subsystems (like SELinux) that need to observe kernel behavior.
-Using the markers for system audit (SELinux) would require to pass a
-variable by address that would be later checked by the marked routine.
+Using the markers for system audit (SELinux) would require passing a
+variable by address so that it could be checked by the marked routine.
* Usage
@@ -52,15 +49,15 @@ Where :
Connecting a function (probe) to a marker is done by providing a probe
(function to call) for the specific marker through marker_set_probe(). It will
automatically connect the function and enable the marker site. Removing a probe
-is done through marker_remove_probe(). Probe removal is preempt safe because
+is done through marker_remove_probe(). Probe removal is preempt-safe because
preemption is disabled around the probe call. See the "Probe example" section
below for a sample probe module.
-The marker mechanism supports multiple instances of the same marker.
-Markers can be put in inline functions, inlined static functions and
+The marker mechanism supports inserting multiple instances of the same marker.
+Markers can be put in inline functions, inlined static functions, and
unrolled loops.
-Note : It is safe to put markers within preempt-safe code : preempt_enable()
+Note: It is safe to put markers within preempt-safe code : preempt_enable()
will not call the scheduler due to the tests in preempt_schedule().
@@ -68,23 +65,23 @@ will not call the scheduler due to the t
You will find, in asm-*/marker.h, optimisations for given architectures
(currently i386 and powerpc). They use a load immediate instead of a data load,
-which saves a data cache hit, but also requires cross CPU code modification. In
-order to support embedded systems which use read-only memory for
their code, the
+which saves a data cache hit, but also requires cross-CPU code modification. In
+order to support embedded systems that use read-only memory for their code, the
optimization can be disabled through menu options.
The MF_* flags can be used to control the type of marker. See the
include/marker.h header for the list of flags. They can be specified as the
-first parameter of the _trace_mark() macro, such as the following example which
+first parameter of the _trace_mark() macro, as in the following example, which
is safe with respect to lockdep.c (useful for marking lockdep.c and printk
functions).
_trace_mark(MF_DEFAULT | ~MF_LOCKDEP, subsystem_eventb, MARK_NOARGS);
-Another example is to specify that a specific marker must never call printk :
+Another example is to specify that a specific marker must never call printk:
_trace_mark(MF_DEFAULT | ~MF_PRINTK, subsystem_eventc,
"%d %s", someint, somestring,);
-Flag compatibility is checked before connecting the probe to the marker : the
+Flag compatibility is checked before connecting the probe to the marker: the
right flags must be given to _marker_set_enable().
next prev parent reply other threads:[~2007-05-10 15:51 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-10 1:55 [patch 00/10] Linux Kernel Markers for 2.6.21-mm2 Mathieu Desnoyers
2007-05-10 1:55 ` [patch 01/10] Linux Kernel Markers - Add kconfig menus for the marker code Mathieu Desnoyers
2007-05-10 6:57 ` Christoph Hellwig
2007-05-10 1:55 ` [patch 02/10] Linux Kernel Markers, architecture independent code Mathieu Desnoyers
2007-05-10 5:10 ` Alexey Dobriyan
2007-05-10 12:58 ` Mathieu Desnoyers
2007-05-10 13:12 ` Mathieu Desnoyers
2007-05-10 19:00 ` Alexey Dobriyan
2007-05-10 19:46 ` Mathieu Desnoyers
2007-05-10 1:55 ` [patch 03/10] Allow userspace applications to use marker.h to parse the markers section in the kernel binary Mathieu Desnoyers
2007-05-10 6:51 ` Christoph Hellwig
2007-05-10 22:14 ` David Smith
2007-06-23 8:09 ` Christoph Hellwig
2007-06-23 9:25 ` Alan Cox
2007-06-23 9:32 ` Christoph Hellwig
2007-06-23 9:49 ` Alan Cox
2007-06-23 10:06 ` Christoph Hellwig
2007-06-23 14:55 ` Alan Cox
2007-05-10 1:55 ` [patch 04/10] Linux Kernel Markers - PowerPC optimized version Mathieu Desnoyers
2007-05-10 6:57 ` Christoph Hellwig
2007-05-10 1:56 ` [patch 05/10] Linux Kernel Markers - i386 " Mathieu Desnoyers
2007-05-10 9:06 ` Andi Kleen
2007-05-10 15:55 ` Mathieu Desnoyers
2007-05-10 16:28 ` Alan Cox
2007-05-10 16:59 ` Mathieu Desnoyers
2007-05-11 4:57 ` Ananth N Mavinakayanahalli
2007-05-11 18:55 ` Mathieu Desnoyers
2007-05-12 5:29 ` Suparna Bhattacharya
2007-05-11 6:04 ` Andi Kleen
2007-05-11 18:02 ` Mathieu Desnoyers
2007-05-11 21:56 ` Alan Cox
2007-05-13 15:20 ` Mathieu Desnoyers
2007-05-10 1:56 ` [patch 06/10] Linux Kernel Markers - Non optimized architectures Mathieu Desnoyers
2007-05-10 5:13 ` Alexey Dobriyan
2007-05-10 6:56 ` Christoph Hellwig
2007-05-10 13:11 ` Mathieu Desnoyers
2007-05-10 13:40 ` Alan Cox
2007-05-10 14:25 ` Mathieu Desnoyers
2007-05-10 15:33 ` Nicholas Berry
2007-05-10 16:09 ` Alan Cox
2007-05-10 1:56 ` [patch 07/10] Linux Kernel Markers - Documentation Mathieu Desnoyers
2007-05-10 6:58 ` Christoph Hellwig
2007-05-10 11:41 ` Alan Cox
2007-05-10 11:41 ` Christoph Hellwig
2007-05-10 12:48 ` Alan Cox
2007-05-10 12:52 ` Pekka Enberg
2007-05-10 13:04 ` Alan Cox
2007-05-10 13:16 ` Pekka J Enberg
2007-05-10 13:43 ` Alan Cox
2007-05-10 14:04 ` Pekka J Enberg
2007-05-10 14:12 ` Mathieu Desnoyers
2007-05-10 14:14 ` Mathieu Desnoyers
2007-05-11 15:05 ` Valdis.Kletnieks
2007-05-10 12:00 ` Christoph Hellwig
2007-05-10 15:51 ` Scott Preece [this message]
2007-05-10 1:56 ` [patch 08/10] Defines the linker macro EXTRA_RWDATA for the marker data section Mathieu Desnoyers
2007-05-10 1:56 ` [patch 09/10] Linux Kernel Markers - Use EXTRA_RWDATA in architectures Mathieu Desnoyers
2007-05-10 1:56 ` [patch 10/10] Port of blktrace to the Linux Kernel Markers Mathieu Desnoyers
2007-05-10 6:53 ` Christoph Hellwig
2007-05-10 9:20 ` Jens Axboe
2007-05-10 2:30 ` [patch 00/10] Linux Kernel Markers for 2.6.21-mm2 Andrew Morton
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