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authorMatti Linnanvuori <mattilinnanvuori@yahoo.com>2008-05-13 11:31:47 -0400
committerRusty Russell <rusty@rustcorp.com.au>2008-05-22 23:09:34 -0400
commit4d2e7d0d77e4e1e8a21cc990c607985fdba20e66 (patch)
tree4a5c3bd6c4e1f34d493146c1657d7fbeaa397cdc /Documentation/DocBook
parent34e4e2fef4c7a2f7699b3d25e48d871d3ac4c3e7 (diff)
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)
Diffstat (limited to 'Documentation/DocBook')
-rw-r--r--Documentation/DocBook/kernel-locking.tmpl25
1 files changed, 25 insertions, 0 deletions
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 @@
703</sect1> 703</sect1>
704</chapter> 704</chapter>
705 705
706<chapter id="trylock-functions">
707 <title>The trylock Functions</title>
708 <para>
709 There are functions that try to acquire a lock only once and immediately
710 return a value telling about success or failure to acquire the lock.
711 They can be used if you need no access to the data protected with the lock
712 when some other thread is holding the lock. You should acquire the lock
713 later if you then need access to the data protected with the lock.
714 </para>
715
716 <para>
717 <function>spin_trylock()</function> does not spin but returns non-zero if
718 it acquires the spinlock on the first try or 0 if not. This function can
719 be used in all contexts like <function>spin_lock</function>: you must have
720 disabled the contexts that might interrupt you and acquire the spin lock.
721 </para>
722
723 <para>
724 <function>mutex_trylock()</function> does not suspend your task
725 but returns non-zero if it could lock the mutex on the first try
726 or 0 if not. This function cannot be safely used in hardware or software
727 interrupt contexts despite not sleeping.
728 </para>
729</chapter>
730
706 <chapter id="Examples"> 731 <chapter id="Examples">
707 <title>Common Examples</title> 732 <title>Common Examples</title>
708 <para> 733 <para>