Re: [PATCH v5 1/8] smp: Run functions concurrently in smp_call_function_many_cond()

[Nadav Amit <namit@vmware.com>]

> On Feb 18, 2021, at 12:09 AM, Christoph Hellwig <hch@infradead.org> wrote:
> 
> On Tue, Feb 09, 2021 at 02:16:46PM -0800, Nadav Amit wrote:
>> +/*
>> + * Flags to be used as scf_flags argument of smp_call_function_many_cond().
>> + */
>> +#define SCF_WAIT	(1U << 0)	/* Wait until function execution completed */
>> +#define SCF_RUN_LOCAL	(1U << 1)	/* Run also locally if local cpu is set in cpumask */
> 
> Can you move the comments on top of the defines to avoid the crazy
> long lines?
> 
>> +	if (cpu_online(this_cpu) && !oops_in_progress && !early_boot_irqs_disabled)
> 
> Another pointlessly overly long line, with various more following.
> 
>> EXPORT_SYMBOL(on_each_cpu_cond_mask);
> 
> This isn't used by any modular code, so maybe throw in a patch to drop
> the export?

I prefer to export on_each_cpu_cond_mask() and instead turn the users
(on_each_cpu(), on_each_cpu_mask() and on_each_cpu_cond()) into inline
functions in smp.h. Otherwise, the call-chain becomes longer for no reason.
Let me know if you object.

So I will add something like:

-- >8 --

Author: Nadav Amit <namit@vmware.com>
Date:   Tue Feb 16 11:04:30 2021 -0800

    smp: inline on_each_cpu_cond() and on_each_cpu_cond_mask()
    
    Suggested-by: Peter Zijlstra <peterz@infradead.org>
    Signed-off-by: Nadav Amit <namit@vmware.com>

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 70c6f6284dcf..84a0b4828f66 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -50,30 +50,52 @@ extern unsigned int total_cpus;
 int smp_call_function_single(int cpuid, smp_call_func_t func, void *info,
                             int wait);
 
+void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func,
+                          void *info, bool wait, const struct cpumask *mask);
+
+int smp_call_function_single_async(int cpu, call_single_data_t *csd);
+
 /*
  * Call a function on all processors
  */
-void on_each_cpu(smp_call_func_t func, void *info, int wait);
+static inline void on_each_cpu(smp_call_func_t func, void *info, int wait)
+{
+       on_each_cpu_cond_mask(NULL, func, info, wait, cpu_online_mask);
+}
 
-/*
- * Call a function on processors specified by mask, which might include
- * the local one.
+/**
+ * on_each_cpu_mask(): Run a function on processors specified by
+ * cpumask, which may include the local processor.
+ * @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.  The
+ * exception is that it may be used during early boot while
+ * early_boot_irqs_disabled is set.
  */
-void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
-               void *info, bool wait);
+static inline void on_each_cpu_mask(const struct cpumask *mask,
+                                   smp_call_func_t func, void *info, bool wait)
+{
+       on_each_cpu_cond_mask(NULL, func, info, wait, mask);
+}
 
 /*
  * Call a function on each processor for which the supplied function
  * cond_func returns a positive value. This may include the local
- * processor.
+ * processor.  May be used during early boot while early_boot_irqs_disabled is
+ * set. Use local_irq_save/restore() instead of local_irq_disable/enable().
  */
-void on_each_cpu_cond(smp_cond_func_t cond_func, smp_call_func_t func,
-                     void *info, bool wait);
-
-void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func,
-                          void *info, bool wait, const struct cpumask *mask);
-
-int smp_call_function_single_async(int cpu, call_single_data_t *csd);
+static inline void on_each_cpu_cond(smp_cond_func_t cond_func,
+                                   smp_call_func_t func, void *info, bool wait)
+{
+       on_each_cpu_cond_mask(cond_func, func, info, wait, cpu_online_mask);
+}
 
 #ifdef CONFIG_SMP
 
diff --git a/kernel/smp.c b/kernel/smp.c
index 629f1f7b80db..a75f3d1dd1b7 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -843,55 +843,6 @@ void __init smp_init(void)
        smp_cpus_done(setup_max_cpus);
 }
 
-/*
- * Call a function on all processors.  May be used during early boot while
- * early_boot_irqs_disabled is set.  Use local_irq_save/restore() instead
- * of local_irq_disable/enable().
- */
-void on_each_cpu(smp_call_func_t func, void *info, int wait)
-{
-       unsigned long flags;
-
-       preempt_disable();
-       smp_call_function(func, info, wait);
-       local_irq_save(flags);
-       func(info);
-       local_irq_restore(flags);
-       preempt_enable();
-}
-EXPORT_SYMBOL(on_each_cpu);
-
-/**
- * on_each_cpu_mask(): Run a function on processors specified by
- * cpumask, which may include the local processor.
- * @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.  The
- * exception is that it may be used during early boot while
- * early_boot_irqs_disabled is set.
- */
-void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func,
-                       void *info, bool wait)
-{
-       unsigned int scf_flags;
-
-       scf_flags = SCF_RUN_LOCAL;
-       if (wait)
-               scf_flags |= SCF_WAIT;
-
-       preempt_disable();
-       smp_call_function_many_cond(mask, func, info, scf_flags, NULL);
-       preempt_enable();
-}
-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
@@ -928,13 +879,6 @@ void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func,
 }
 EXPORT_SYMBOL(on_each_cpu_cond_mask);
 
-void on_each_cpu_cond(smp_cond_func_t cond_func, smp_call_func_t func,
-                     void *info, bool wait)
-{
-       on_each_cpu_cond_mask(cond_func, func, info, wait, cpu_online_mask);
-}
-EXPORT_SYMBOL(on_each_cpu_cond);
-
 static void do_nothing(void *unused)
 {
 }