Update the documentation to reflect changes due to the availability of
this_cpu operations.
Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
properly. It also stresses on the precautions that must be taken when reading
those local variables across CPUs when the order of memory writes matters.
properly. It also stresses on the precautions that must be taken when reading
those local variables across CPUs when the order of memory writes matters.
+Note that local_t based operations are not recommended for general kernel use.
+Please use the this_cpu operations instead unless there is really a special purpose.
+Most uses of local_t in the kernel have been replaced by this_cpu operations.
+this_cpu operations combine the relocation with the local_t like semantics in
+a single instruction and yield more compact and faster executing code.
* Purpose of local atomic operations
* Purpose of local atomic operations
local_inc(&get_cpu_var(counters));
put_cpu_var(counters);
local_inc(&get_cpu_var(counters));
put_cpu_var(counters);
-If you are already in a preemption-safe context, you can directly use
-__get_cpu_var() instead.
+If you are already in a preemption-safe context, you can use
+this_cpu_ptr() instead.
- local_inc(&__get_cpu_var(counters));
+ local_inc(this_cpu_ptr(&counters));
{
/* Increment the counter from a non preemptible context */
printk("Increment on cpu %d\n", smp_processor_id());
{
/* Increment the counter from a non preemptible context */
printk("Increment on cpu %d\n", smp_processor_id());
- local_inc(&__get_cpu_var(counters));
+ local_inc(this_cpu_ptr(&counters));
/* This is what incrementing the variable would look like within a
* preemptible context (it disables preemption) :
/* This is what incrementing the variable would look like within a
* preemptible context (it disables preemption) :