generic-ipi: Add smp_call_function_any()

Andrew points out that acpi-cpufreq uses cpumask_any, when it really
would prefer to use the same CPU if possible (to avoid an IPI).  In
general, this seems a good idea to offer.

[ tglx: Documented selection preference and Inlined the UP case to
  	avoid the copy of smp_call_function_single() and the extra
  	EXPORT ]

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Zhao Yakui <yakui.zhao@intel.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 55 insertions, 1 deletions

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 39c64bae776d..7a0570e6a596 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -76,6 +76,9 @@ void smp_call_function_many(const struct cpumask *mask,
 void __smp_call_function_single(int cpuid, struct call_single_data *data,
                                 int wait);
 
+int smp_call_function_any(const struct cpumask *mask,
+                          void (*func)(void *info), void *info, int wait);
+
 /*
  * Generic and arch helpers
  */
@@ -137,9 +140,15 @@ static inline void smp_send_reschedule(int cpu) { }
 #define smp_prepare_boot_cpu()                  do {} while (0)
 #define smp_call_function_many(mask, func, info, wait) \
                         (up_smp_call_function(func, info))
-static inline void init_call_single_data(void)
+static inline void init_call_single_data(void) { }
+
+static inline int
+smp_call_function_any(const struct cpumask *mask, void (*func)(void *info),
+                      void *info, int wait)
 {
+        return smp_call_function_single(0, func, info, wait);
 }
+
 #endif /* !SMP */
 
 /*
diff --git a/kernel/smp.c b/kernel/smp.c
index 8bd618f0364d..a8c76069cf50 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -319,6 +319,51 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
 }
 EXPORT_SYMBOL(smp_call_function_single);
 
+/*
+ * smp_call_function_any - Run a function on any of the given cpus
+ * @mask: The mask of cpus it can run on.
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @wait: If true, wait until function has completed.
+ *
+ * Returns 0 on success, else a negative status code (if no cpus were online).
+ * Note that @wait will be implicitly turned on in case of allocation failures,
+ * since we fall back to on-stack allocation.
+ *
+ * Selection preference:
+ *      1) current cpu if in @mask
+ *      2) any cpu of current node if in @mask
+ *      3) any other online cpu in @mask
+ */
+int smp_call_function_any(const struct cpumask *mask,
+                          void (*func)(void *info), void *info, int wait)
+{
+        unsigned int cpu;
+        const struct cpumask *nodemask;
+        int ret;
+
+        /* Try for same CPU (cheapest) */
+        cpu = get_cpu();
+        if (cpumask_test_cpu(cpu, mask))
+                goto call;
+
+        /* Try for same node. */
+        nodemask = cpumask_of_node(cpu);
+        for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids;
+             cpu = cpumask_next_and(cpu, nodemask, mask)) {
+                if (cpu_online(cpu))
+                        goto call;
+        }
+
+        /* Any online will do: smp_call_function_single handles nr_cpu_ids. */
+        cpu = cpumask_any_and(mask, cpu_online_mask);
+call:
+        ret = smp_call_function_single(cpu, func, info, wait);
+        put_cpu();
+        return ret;
+}
+EXPORT_SYMBOL_GPL(smp_call_function_any);
+
 /**
  * __smp_call_function_single(): Run a function on another CPU
  * @cpu: The CPU to run on.