Documentation/process/volatile-considered-harmful.rst

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9 sometimes tempted to use it in kernel code when shared data structures are
11 as a sort of easy atomic variable, which they are not.  The use of volatile in
19 all optimization-related problems in a more efficient way.
24 need to use volatile as well.  If volatile is still necessary, there is
25 almost certainly a bug in the code somewhere.  In properly-written kernel
38 primitives act as memory barriers - they are explicitly written to do so -
50 unnecessary - and potentially harmful.
52 The volatile storage class was originally meant for memory-mapped I/O
61 Another situation where one might be tempted to use volatile is
62 when the processor is busy-waiting on the value of a variable.  The right
70 barrier, so, once again, volatile is unnecessary.  Of course, busy-
71 waiting is generally an anti-social act to begin with.
73 There are still a few rare situations where volatile makes sense in the
76   - The above-mentioned accessor functions might use volatile on
81   - Inline assembly code which changes memory, but which has no other
85   - The jiffies variable is special in that it can have a different value
92   - Pointers to data structures in coherent memory which might be modified
93     by I/O devices can, sometimes, legitimately be volatile.  A ring buffer
99 result, the use of volatile is likely to be seen as a bug and will bring
100 additional scrutiny to the code.  Developers who are tempted to use
104 Patches to remove volatile variables are generally welcome - as long as