---

yaml
---
r: 97202
b: refs/heads/master
c: 4d2e7d0
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 34e4e2fef4c7a2f7699b3d25e48d871d3ac4c3e7
+refs/heads/master: 4d2e7d0d77e4e1e8a21cc990c607985fdba20e66

trunk/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>