linux-kernel - [RFC PATCH 2/2] smp: Change signatures to use call_single_data

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Message-Id: <20230511085836.579679-2-leobras@redhat.com>
Date:   Thu, 11 May 2023 05:58:38 -0300
From:   Leonardo Bras <leobras@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Valentin Schneider <vschneid@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Yury Norov <yury.norov@...il.com>,
        Leonardo Bras <leobras@...hat.com>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 2/2] smp: Change signatures to use call_single_data_t

Every caller of smp_call_function_single_async() now makes use
of call_single_data_t, which is a size-aligned typedef of
struct __call_single_data.

Changing smp_call_function_single_async() csd parameter to
call_single_data_t makes possible to warn future callers if they
are using an unaligned csd, which can cause it to be split between 2
cachelines, which is usually bad for performance.

Also, for the same reason, change generic_exec_single().

Signed-off-by: Leonardo Bras <leobras@...hat.com>
---
 kernel/smp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index ab3e5dad6cfe..919387be6d4e 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -361,7 +361,7 @@ void __smp_call_single_queue(int cpu, struct llist_node *node)
  * for execution on the given CPU. data must already have
  * ->func, ->info, and ->flags set.
  */
-static int generic_exec_single(int cpu, struct __call_single_data *csd)
+static int generic_exec_single(int cpu, call_single_data_t *csd)
 {
 	if (cpu == smp_processor_id()) {
 		smp_call_func_t func = csd->func;
@@ -645,7 +645,7 @@ EXPORT_SYMBOL(smp_call_function_single);
  *
  * Return: %0 on success or negative errno value on error
  */
-int smp_call_function_single_async(int cpu, struct __call_single_data *csd)
+int smp_call_function_single_async(int cpu, call_single_data_t *csd)
 {
 	int err = 0;
 
-- 
2.40.1