linux-kernel - [PATCH v4 1/2] smp: Fix the comments of smp_call_function

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Date:   Thu, 16 Dec 2021 22:40:52 +0800
From:   Zhen Lei <thunder.leizhen@...wei.com>
To:     Ingo Molnar <mingo@...nel.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Peter Zijlstra <peterz@...radead.org>,
        <linux-kernel@...r.kernel.org>
CC:     Zhen Lei <thunder.leizhen@...wei.com>,
        Nadav Amit <namit@...are.com>,
        "Dave Hansen" <dave.hansen@...ux.intel.com>
Subject: [PATCH v4 1/2] smp: Fix the comments of smp_call_function_many()

As commit a32a4d8a815c ("smp: Run functions concurrently in
smp_call_function_many_cond()") itself says:
                  "Keep other smp_call_function_many() semantic as it is
today for backward compatibility: the called function is not executed in
this case locally."

It's clear that, the function header comments of smp_call_function_many()
does not need to be changed.

So move the comment about 'scf_flags' to smp_call_function_many_cond(),
and restore the original comments of smp_call_function_many(). The
comments have been simplified slightly to avoid duplication. And the
description of other parameters of smp_call_function_many_cond() is added.

Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
---
 kernel/smp.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index 01a7c1706a58b1d..1e5221fe200296a 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -853,14 +853,26 @@ int smp_call_function_any(const struct cpumask *mask,
 EXPORT_SYMBOL_GPL(smp_call_function_any);
 
 /*
- * Flags to be used as scf_flags argument of smp_call_function_many_cond().
- *
  * %SCF_WAIT:		Wait until function execution is completed
  * %SCF_RUN_LOCAL:	Run also locally if local cpu is set in cpumask
  */
 #define SCF_WAIT	(1U << 0)
 #define SCF_RUN_LOCAL	(1U << 1)
 
+/**
+ * smp_call_function_many_cond() - Run a function on a set of CPUs.
+ * @mask:	The set of cpus to run on (only runs on online subset).
+ *		Whether to allow execution on the local CPU is also controlled
+ *		by @scf_flags.
+ * @func:	The function to run on all applicable CPUs.
+ * @info:	An arbitrary pointer to pass to @func.
+ * @scf_flags:	Bitmask that controls the operation. Such as SCF_WAIT,
+ *		SCF_RUN_LOCAL.
+ * @cond_func:	A callback function that is passed a cpu id and the info
+ *		parameter. The function should return a blooean value
+ *		indicating whether @func will be executed on the specified CPU.
+ *		If @cond_func is NULL, that means unconditional, always true.
+ */
 static void smp_call_function_many_cond(const struct cpumask *mask,
 					smp_call_func_t func, void *info,
 					unsigned int scf_flags,
@@ -972,14 +984,12 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
 }
 
 /**
- * smp_call_function_many(): Run a function on a set of CPUs.
+ * 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: Bitmask that controls the operation. If %SCF_WAIT is set, wait
- *        (atomically) until function has completed on other CPUs. If
- *        %SCF_RUN_LOCAL is set, the function will also be run locally
- *        if the local CPU is set in the @cpumask.
+ * @wait: If true, wait (atomically) until function has completed
+ *        on other CPUs.
  *
  * If @wait is true, then returns once @func has returned.
  *
-- 
2.25.1