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author | Ingo Molnar <mingo@elte.hu> | 2006-01-09 15:59:20 -0800 |
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committer | Ingo Molnar <mingo@hera.kernel.org> | 2006-01-09 15:59:20 -0800 |
commit | f3f54ffa703c6298240ffd69616451d645bae4d5 (patch) | |
tree | 0f66c760d21ab3c94b4f0be4229f458c0a3fd9c2 /Documentation/DocBook | |
parent | 6053ee3b32e3437e8c1e72687850f436e779bd49 (diff) | |
download | kernel_samsung_espresso10-f3f54ffa703c6298240ffd69616451d645bae4d5.zip kernel_samsung_espresso10-f3f54ffa703c6298240ffd69616451d645bae4d5.tar.gz kernel_samsung_espresso10-f3f54ffa703c6298240ffd69616451d645bae4d5.tar.bz2 |
[PATCH] mutex subsystem, documentation
Add mutex design related documentation.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Diffstat (limited to 'Documentation/DocBook')
-rw-r--r-- | Documentation/DocBook/kernel-locking.tmpl | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/Documentation/DocBook/kernel-locking.tmpl b/Documentation/DocBook/kernel-locking.tmpl index 90dc2de..158ffe9 100644 --- a/Documentation/DocBook/kernel-locking.tmpl +++ b/Documentation/DocBook/kernel-locking.tmpl @@ -222,7 +222,7 @@ <title>Two Main Types of Kernel Locks: Spinlocks and Semaphores</title> <para> - There are two main types of kernel locks. The fundamental type + There are three main types of kernel locks. The fundamental type is the spinlock (<filename class="headerfile">include/asm/spinlock.h</filename>), which is a very simple single-holder lock: if you can't get the @@ -230,16 +230,22 @@ very small and fast, and can be used anywhere. </para> <para> - The second type is a semaphore + The second type is a mutex + (<filename class="headerfile">include/linux/mutex.h</filename>): it + is like a spinlock, but you may block holding a mutex. + If you can't lock a mutex, your task will suspend itself, and be woken + up when the mutex is released. This means the CPU can do something + else while you are waiting. There are many cases when you simply + can't sleep (see <xref linkend="sleeping-things"/>), and so have to + use a spinlock instead. + </para> + <para> + The third type is a semaphore (<filename class="headerfile">include/asm/semaphore.h</filename>): it can have more than one holder at any time (the number decided at initialization time), although it is most commonly used as a - single-holder lock (a mutex). If you can't get a semaphore, - your task will put itself on the queue, and be woken up when the - semaphore is released. This means the CPU will do something - else while you are waiting, but there are many cases when you - simply can't sleep (see <xref linkend="sleeping-things"/>), and so - have to use a spinlock instead. + single-holder lock (a mutex). If you can't get a semaphore, your + task will be suspended and later on woken up - just like for mutexes. </para> <para> Neither type of lock is recursive: see |