powerpc: Avoid extra indirect function call in sending IPIs

On many platforms (including pSeries), smp_ops->message_pass is always
smp_muxed_ipi_message_pass.  This changes arch/powerpc/kernel/smp.c so
that if smp_ops->message_pass is NULL, it calls smp_muxed_ipi_message_pass
directly.

This means that a platform doesn't need to set both .message_pass and
.cause_ipi, only one of them.  It is a slight performance improvement
in that it gets rid of an indirect function call at the expense of a
predictable conditional branch.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 14 insertions, 4 deletions

diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index 8ebc6700b98d..2975f64cf310 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -238,15 +238,25 @@ irqreturn_t smp_ipi_demux(void)
 }
 #endif /* CONFIG_PPC_SMP_MUXED_IPI */
 
+static inline void do_message_pass(int cpu, int msg)
+{
+        if (smp_ops->message_pass)
+                smp_ops->message_pass(cpu, msg);
+#ifdef CONFIG_PPC_SMP_MUXED_IPI
+        else
+                smp_muxed_ipi_message_pass(cpu, msg);
+#endif
+}
+
 void smp_send_reschedule(int cpu)
 {
         if (likely(smp_ops))
-                smp_ops->message_pass(cpu, PPC_MSG_RESCHEDULE);
+                do_message_pass(cpu, PPC_MSG_RESCHEDULE);
 }
 
 void arch_send_call_function_single_ipi(int cpu)
 {
-        smp_ops->message_pass(cpu, PPC_MSG_CALL_FUNC_SINGLE);
+        do_message_pass(cpu, PPC_MSG_CALL_FUNC_SINGLE);
 }
 
 void arch_send_call_function_ipi_mask(const struct cpumask *mask)
@@ -254,7 +264,7 @@ void arch_send_call_function_ipi_mask(const struct cpumask *mask)
         unsigned int cpu;
 
         for_each_cpu(cpu, mask)
-                smp_ops->message_pass(cpu, PPC_MSG_CALL_FUNCTION);
+                do_message_pass(cpu, PPC_MSG_CALL_FUNCTION);
 }
 
 #if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC)
@@ -268,7 +278,7 @@ void smp_send_debugger_break(void)
 
         for_each_online_cpu(cpu)
                 if (cpu != me)
-                        smp_ops->message_pass(cpu, PPC_MSG_DEBUGGER_BREAK);
+                        do_message_pass(cpu, PPC_MSG_DEBUGGER_BREAK);
 }
 #endif