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>Avoiding Locks: Atomic Operations</H1
><P
> There are a number of atomic operations defined in
<TT
CLASS="FILENAME"
>include/asm/atomic.h</TT
>: these
are guaranteed to be seen atomically from all CPUs in the system, thus
avoiding races. If your shared data consists of a single counter, say,
these operations might be simpler than using spinlocks (although for
anything non-trivial using spinlocks is clearer).
</P
><P
> Note that the atomic operations do in general not act as memory
barriers. Instead you can insert a memory barrier before or
after <TT
CLASS="FUNCTION"
>atomic_inc()</TT
> or
<TT
CLASS="FUNCTION"
>atomic_dec()</TT
> by inserting
<TT
CLASS="FUNCTION"
>smp_mb__before_atomic_inc()</TT
>,
<TT
CLASS="FUNCTION"
>smp_mb__after_atomic_inc()</TT
>,
<TT
CLASS="FUNCTION"
>smp_mb__before_atomic_dec()</TT
> or
<TT
CLASS="FUNCTION"
>smp_mb__after_atomic_dec()</TT
>
respectively. The advantage of using those macros instead of
<TT
CLASS="FUNCTION"
>smp_mb()</TT
> is, that they are cheaper on some
platforms.
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