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authorMatti Linnanvuori <mattilinnanvuori@yahoo.com>2008-05-13 18:31:47 +0300
committerRusty Russell <rusty@rustcorp.com.au>2008-05-23 13:09:34 +1000
commit4d2e7d0d77e4e1e8a21cc990c607985fdba20e66 (patch)
tree4a5c3bd6c4e1f34d493146c1657d7fbeaa397cdc /Documentation/DocBook/kernel-locking.tmpl
parent34e4e2fef4c7a2f7699b3d25e48d871d3ac4c3e7 (diff)
downloadkernel-4d2e7d0d77e4e1e8a21cc990c607985fdba20e66.tar.gz
doc: add a chapter about trylock functions [Bug 9011]
Add a chapter about trylock functions. http://bugzilla.kernel.org/show_bug.cgi?id=9011 Signed-off-by: Matti Linnanvuori <mattilinnanvuori@yahoo.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (removed down_trylock)
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diff --git a/Documentation/DocBook/kernel-locking.tmpl b/Documentation/DocBook/kernel-locking.tmpl
index 77c42f40be5d..2510763295d0 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>