29 Jul
2004
29 Jul
'04
5:40 p.m.
On Thu, Jul 29, 2004 at 03:17:52PM -0400, Scott Wood wrote:
On Thu, Jul 29, 2004 at 11:36:26AM -0700, Bill Huey
wrote:
There are legitimate reasons to use smp_processor_id() outside of a
non-preemptible region, though. These include debugging
printks/logging, and situations where the awareness of CPU is for
optimization rather than correctness (for example, using per-cpu data
with per-cpu locks, which are only contended if preemption occurs, or
per-cpu counters incremented with atomic operations (or where counter
accuracy is not critical)).
The detection mechanism we used in 2.4 was simply to grep for
smp_processor_id and check/fix everything manually (which is somewhat
tedious, but there aren't *too* many instances in core code, and many
uses are similar to one another).
That's a better method. But if there's a need for a kind of runtime
detector, I guess you could do that. The use of smp_processor_id() should
be seldom enough that manually fixing all of the points really should
be the solution.
bill