On 07/23/2015 12:42 PM, Frederic Weisbecker wrote:
+unsigned long __tick_nohz_set_tick_dependency(enum tick_dependency_bit bit,
+ unsigned long *dep)
+{
+ unsigned long prev;
+ unsigned long old = *dep;
+ unsigned long mask = BIT_MASK(bit);
+
+ while ((prev = cmpxchg(dep, old, old | mask)) != old) {
+ old = prev;
+ cpu_relax();
+ }
+
+ return prev;
+}
Why not use set_bit() here? It is suitably atomic.
+ /*
+ * We need the IPIs to be sent from sane process context.
+ * The posix cpu timers are always set with irqs disabled.
+ */
The block comment indentation is not quite right here.
+void tick_nohz_set_tick_dependency_cpu(enum tick_dependency_bit bit, int cpu)
+{
+ unsigned long prev;
+ struct tick_sched *ts;
+
+ ts = per_cpu_ptr(&tick_cpu_sched, cpu);
+
+ prev = __tick_nohz_set_tick_dependency(bit, &ts->tick_dependency);
+ if (!prev)
+ tick_nohz_full_kick_cpu(cpu);
+}
I could imagine arguments for a WARN_ON() if cpu == smp_processor_id()
here, since then you should be using the _thiscpu() variant.
Or, you could transparently call the _thiscpu() variant in that case.
I think some comment explaining why the approach you chose is better
than those alternatives would be helpful here, perhaps.
--
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com
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