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Diffstat (limited to 'Documentation/DocBook/kernel-locking.tmpl')
| -rw-r--r-- | Documentation/DocBook/kernel-locking.tmpl | 25 |
1 files changed, 24 insertions, 1 deletions
diff --git a/Documentation/DocBook/kernel-locking.tmpl b/Documentation/DocBook/kernel-locking.tmpl index 2e9d6b41f034..b683710f7039 100644 --- a/Documentation/DocBook/kernel-locking.tmpl +++ b/Documentation/DocBook/kernel-locking.tmpl @@ -290,7 +290,7 @@ <para> If you have a data structure which is only ever accessed from user context, then you can use a simple semaphore - (<filename>linux/asm/semaphore.h</filename>) to protect it. This + (<filename>include/asm/semaphore.h</filename>) to protect it. This is the most trivial case: you initialize the semaphore to the number of resources available (usually 1), and call <function>down_interruptible()</function> to grab the semaphore, and @@ -703,6 +703,29 @@ </sect1> </chapter> +<chapter id="try-variants"> + <title>The try variants</title> + + <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. + </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. + </para> + + <para> + <function>down_trylock()</function> does not suspend your task + but returns 0 if it could get the semaphore on the first try or + non-zero if not. The return value is the inverse of that of + <function>spin_trylock()</function> and <function>mutex_trylock() + </function>. + </para> +</chapter> + <chapter id="Examples"> <title>Common Examples</title> <para> |