1 files changed, 61 insertions, 0 deletions

diff --git a/kernel/smp.c b/kernel/smp.c
index a081e6ce0e0a..2f8b10ecf759 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -730,3 +730,64 @@ void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
         put_cpu();
 }
 EXPORT_SYMBOL(on_each_cpu_mask);
+
+/*
+ * on_each_cpu_cond(): Call a function on each processor for which
+ * the supplied function cond_func returns true, optionally waiting
+ * for all the required CPUs to finish. This may include the local
+ * processor.
+ * @cond_func:  A callback function that is passed a cpu id and
+ *              the the info parameter. The function is called
+ *              with preemption disabled. The function should
+ *              return a blooean value indicating whether to IPI
+ *              the specified CPU.
+ * @func:       The function to run on all applicable CPUs.
+ *              This must be fast and non-blocking.
+ * @info:       An arbitrary pointer to pass to both functions.
+ * @wait:       If true, wait (atomically) until function has
+ *              completed on other CPUs.
+ * @gfp_flags:  GFP flags to use when allocating the cpumask
+ *              used internally by the function.
+ *
+ * The function might sleep if the GFP flags indicates a non
+ * atomic allocation is allowed.
+ *
+ * Preemption is disabled to protect against CPUs going offline but not online.
+ * CPUs going online during the call will not be seen or sent an IPI.
+ *
+ * You must not call this function with disabled interrupts or
+ * from a hardware interrupt handler or from a bottom half handler.
+ */
+void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info),
+                        smp_call_func_t func, void *info, bool wait,
+                        gfp_t gfp_flags)
+{
+        cpumask_var_t cpus;
+        int cpu, ret;
+
+        might_sleep_if(gfp_flags & __GFP_WAIT);
+
+        if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
+                preempt_disable();
+                for_each_online_cpu(cpu)
+                        if (cond_func(cpu, info))
+                                cpumask_set_cpu(cpu, cpus);
+                on_each_cpu_mask(cpus, func, info, wait);
+                preempt_enable();
+                free_cpumask_var(cpus);
+        } else {
+                /*
+                 * No free cpumask, bother. No matter, we'll
+                 * just have to IPI them one by one.
+                 */
+                preempt_disable();
+                for_each_online_cpu(cpu)
+                        if (cond_func(cpu, info)) {
+                                ret = smp_call_function_single(cpu, func,
+                                                                info, wait);
+                                WARN_ON_ONCE(!ret);
+                        }
+                preempt_enable();
+        }
+}
+EXPORT_SYMBOL(on_each_cpu_cond);