documentation: Add atomic_long_t to atomic_ops.txt

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
This commit is contained in:
Paul E. McKenney 2014-10-19 12:05:22 -07:00
parent 8b19d1dead
commit 1f7870dd87

View File

@ -7,12 +7,13 @@
maintainers on how to implement atomic counter, bitops, and spinlock
interfaces properly.
The atomic_t type should be defined as a signed integer.
Also, it should be made opaque such that any kind of cast to a normal
C integer type will fail. Something like the following should
suffice:
The atomic_t type should be defined as a signed integer and
the atomic_long_t type as a signed long integer. Also, they should
be made opaque such that any kind of cast to a normal C integer type
will fail. Something like the following should suffice:
typedef struct { int counter; } atomic_t;
typedef struct { long counter; } atomic_long_t;
Historically, counter has been declared volatile. This is now discouraged.
See Documentation/volatile-considered-harmful.txt for the complete rationale.
@ -37,6 +38,9 @@ initializer is used before runtime. If the initializer is used at runtime, a
proper implicit or explicit read memory barrier is needed before reading the
value with atomic_read from another thread.
As with all of the atomic_ interfaces, replace the leading "atomic_"
with "atomic_long_" to operate on atomic_long_t.
The second interface can be used at runtime, as in:
struct foo { atomic_t counter; };