smp: Add a smp_cond_func_t argument to smp_call_function_many()

on_each_cpu_cond_mask() allocates a new CPU mask. The newly allocated
mask is a subset of the provided mask based on the conditional function.

This memory allocation can be avoided by extending smp_call_function_many()
with the conditional function and performing the remote function call based
on the mask and the conditional function.

Rename smp_call_function_many() to smp_call_function_many_cond() and add
the smp_cond_func_t argument. If smp_cond_func_t is provided then it is
used before invoking the function.  Provide smp_call_function_many() with
cond_func set to NULL.  Let on_each_cpu_cond_mask() use
smp_call_function_many_cond().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200117090137.1205765-3-bigeasy@linutronix.de

diff --git a/kernel/smp.c b/kernel/smp.c
index c64044d..e17e634 100644 (file)
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -395,22 +395,9 @@ call:
 }
 EXPORT_SYMBOL_GPL(smp_call_function_any);
 
-/**
- * smp_call_function_many(): Run a function on a set of other CPUs.
- * @mask: The set of cpus to run on (only runs on online subset).
- * @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 (atomically) until function has completed
- *        on other CPUs.
- *
- * If @wait is true, then returns once @func has returned.
- *
- * You must not call this function with disabled interrupts or from a
- * hardware interrupt handler or from a bottom half handler. Preemption
- * must be disabled when calling this function.
- */
-void smp_call_function_many(const struct cpumask *mask,
-                           smp_call_func_t func, void *info, bool wait)
+static void smp_call_function_many_cond(const struct cpumask *mask,
+                                       smp_call_func_t func, void *info,
+                                       bool wait, smp_cond_func_t cond_func)
 {
        struct call_function_data *cfd;
        int cpu, next_cpu, this_cpu = smp_processor_id();
@@ -448,7 +435,8 @@ void smp_call_function_many(const struct cpumask *mask,
 
        /* Fastpath: do that cpu by itself. */
        if (next_cpu >= nr_cpu_ids) {
-               smp_call_function_single(cpu, func, info, wait);
+               if (!cond_func || (cond_func && cond_func(cpu, info)))
+                       smp_call_function_single(cpu, func, info, wait);
                return;
        }
 
@@ -465,6 +453,9 @@ void smp_call_function_many(const struct cpumask *mask,
        for_each_cpu(cpu, cfd->cpumask) {
                call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu);
 
+               if (cond_func && !cond_func(cpu, info))
+                       continue;
+
                csd_lock(csd);
                if (wait)
                        csd->flags |= CSD_FLAG_SYNCHRONOUS;
@@ -486,6 +477,26 @@ void smp_call_function_many(const struct cpumask *mask,
                }
        }
 }
+
+/**
+ * smp_call_function_many(): Run a function on a set of other CPUs.
+ * @mask: The set of cpus to run on (only runs on online subset).
+ * @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 (atomically) until function has completed
+ *        on other CPUs.
+ *
+ * If @wait is true, then returns once @func has returned.
+ *
+ * You must not call this function with disabled interrupts or from a
+ * hardware interrupt handler or from a bottom half handler. Preemption
+ * must be disabled when calling this function.
+ */
+void smp_call_function_many(const struct cpumask *mask,
+                           smp_call_func_t func, void *info, bool wait)
+{
+       smp_call_function_many_cond(mask, func, info, wait, NULL);
+}
 EXPORT_SYMBOL(smp_call_function_many);
 
 /**
@@ -684,33 +695,17 @@ void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func,
                           void *info, bool wait, gfp_t gfp_flags,
                           const struct cpumask *mask)
 {
-       cpumask_var_t cpus;
-       int cpu, ret;
-
-       might_sleep_if(gfpflags_allow_blocking(gfp_flags));
-
-       if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) {
-               preempt_disable();
-               for_each_cpu(cpu, mask)
-                       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_cpu(cpu, mask)
-                       if (cond_func(cpu, info)) {
-                               ret = smp_call_function_single(cpu, func,
-                                                               info, wait);
-                               WARN_ON_ONCE(ret);
-                       }
-               preempt_enable();
+       int cpu = get_cpu();
+
+       smp_call_function_many_cond(mask, func, info, wait, cond_func);
+       if (cpumask_test_cpu(cpu, mask) && cond_func(cpu, info)) {
+               unsigned long flags;
+
+               local_irq_save(flags);
+               func(info);
+               local_irq_restore(flags);
        }
+       put_cpu();
 }
 EXPORT_SYMBOL(on_each_cpu_cond_mask);