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-rw-r--r--Documentation/DocBook/kernel-locking.tmpl25
-rw-r--r--Documentation/DocBook/kgdb.tmpl20
2 files changed, 31 insertions, 14 deletions
diff --git a/Documentation/DocBook/kernel-locking.tmpl b/Documentation/DocBook/kernel-locking.tmpl
index 77c42f40be5..2510763295d 100644
--- a/Documentation/DocBook/kernel-locking.tmpl
+++ b/Documentation/DocBook/kernel-locking.tmpl
@@ -703,6 +703,31 @@
</sect1>
</chapter>
+<chapter id="trylock-functions">
+ <title>The trylock Functions</title>
+ <para>
+ There are functions that try to acquire a lock only once and immediately
+ return a value telling about success or failure to acquire the lock.
+ They can be used if you need no access to the data protected with the lock
+ when some other thread is holding the lock. You should acquire the lock
+ later if you then need access to the data protected with the lock.
+ </para>
+
+ <para>
+ <function>spin_trylock()</function> does not spin but returns non-zero if
+ it acquires the spinlock on the first try or 0 if not. This function can
+ be used in all contexts like <function>spin_lock</function>: you must have
+ disabled the contexts that might interrupt you and acquire the spin lock.
+ </para>
+
+ <para>
+ <function>mutex_trylock()</function> does not suspend your task
+ but returns non-zero if it could lock the mutex on the first try
+ or 0 if not. This function cannot be safely used in hardware or software
+ interrupt contexts despite not sleeping.
+ </para>
+</chapter>
+
<chapter id="Examples">
<title>Common Examples</title>
<para>
diff --git a/Documentation/DocBook/kgdb.tmpl b/Documentation/DocBook/kgdb.tmpl
index 028a8444d95..e8acd1f0345 100644
--- a/Documentation/DocBook/kgdb.tmpl
+++ b/Documentation/DocBook/kgdb.tmpl
@@ -84,10 +84,9 @@
runs an instance of gdb against the vmlinux file which contains
the symbols (not boot image such as bzImage, zImage, uImage...).
In gdb the developer specifies the connection parameters and
- connects to kgdb. Depending on which kgdb I/O modules exist in
- the kernel for a given architecture, it may be possible to debug
- the test machine's kernel with the development machine using a
- rs232 or ethernet connection.
+ connects to kgdb. The type of connection a developer makes with
+ gdb depends on the availability of kgdb I/O modules compiled as
+ builtin's or kernel modules in the test machine's kernel.
</para>
</chapter>
<chapter id="CompilingAKernel">
@@ -223,7 +222,7 @@
</para>
<para>
IMPORTANT NOTE: Using this option with kgdb over the console
- (kgdboc) or kgdb over ethernet (kgdboe) is not supported.
+ (kgdboc) is not supported.
</para>
</sect1>
</chapter>
@@ -249,18 +248,11 @@
(gdb) target remote /dev/ttyS0
</programlisting>
<para>
- Example (kgdb to a terminal server):
+ Example (kgdb to a terminal server on tcp port 2012):
</para>
<programlisting>
% gdb ./vmlinux
- (gdb) target remote udp:192.168.2.2:6443
- </programlisting>
- <para>
- Example (kgdb over ethernet):
- </para>
- <programlisting>
- % gdb ./vmlinux
- (gdb) target remote udp:192.168.2.2:6443
+ (gdb) target remote 192.168.2.2:2012
</programlisting>
<para>
Once connected, you can debug a kernel the way you would debug an