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authorIngo Molnar <mingo@elte.hu>2008-06-16 11:27:45 +0200
committerIngo Molnar <mingo@elte.hu>2008-06-16 11:27:45 +0200
commitd939d2851fd12568e2eabb2916769e8a57ba5c89 (patch)
treef3158a5ddd41541a61126f9e48de1ce89c632f64 /Documentation/DocBook/kernel-locking.tmpl
parent9f5314fb4d556d3132c784d0df47352b2830ca53 (diff)
parent066519068ad2fbe98c7f45552b1f592903a9c8c8 (diff)
Merge branch 'linus' into x86/irqtip-x86-irq-2008-06-16_09.27_Mon
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@@ -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>