Hi Andi,
On 7/19/07, Andi Kleen <[EMAIL PROTECTED]> wrote:
Call a function on a target CPU but do the right thing when
we're already on that CPU. That's the main difference from
smp_call_function_single
which does the wrong thing in this case (erroring out)
I think this is no longer the case, is it? With KVM updates already
merged in latest mainline -git, that modified smp_call_function_single()
behaviour ...
+#ifdef CONFIG_SMP
+/* Similar to smp_call_function_single, but DTRT when we're already
+ on the right CPU. */
+static inline void on_cpu_single(int cpu, void (*func)(void *), void *info)
+{
+ int me = get_cpu();
+ if (cpu == me) {
+ func(info);
+ put_cpu();
+ } else {
+ put_cpu();
+ /* wait is forced on because the me==cpu case above will always
wait */
+ smp_call_function_single(cpu, func, info, 0, 1);
In any case, this is unsafe. smp_call_function_single() -- with the old
semantics, which is what this patch assumes, obviously -- is quite
pointless without its _caller_ disabling preemption around it. So the
put_cpu() must come after the smp_call_function_single, otherwise
you won't even detect the error that might happen, seeing you're
ignoring its return and this wrapper being void-returning.
+ }
+}
+#else
+static inline void on_cpu_single(int cpu, void (*func)(void *), void *info)
+{
WARN_ON(irqs_disabled());
local_irq_disable();
+ func(info);
local_irq_restore();
+}
+#endif
... for the sake of API / behaviour consistency.
But probably you should just drop this ... with smp_call_function_single's
new semantics, I don't see this function growing any users.
Satyam
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