linux-kernel - RE: [PATCH 0/5] Generic smp_call_function(), improvements, and smp_call_function

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Date:	Tue, 25 Mar 2008 09:48:10 -0700
From:	"Luck, Tony" <tony.luck@...el.com>
To:	"Jens Axboe" <jens.axboe@...cle.com>
Cc:	<linux-kernel@...r.kernel.org>, <npiggin@...e.de>,
	<paulus@...ba.org>, <tglx@...utronix.de>, <mingo@...hat.com>
Subject: RE: [PATCH 0/5] Generic smp_call_function(), improvements, and smp_call_function_single()

> So now I/we just need to figure out why the hack to call
> init_call_single_data() is needed. You seem to imply it was being called
> too late, I thought perhaps too early. Where did you stick the
> init_call_single_data() call in?

In ia64 the first calls to smp_call_function_single() are made
while bringing up other cpus ... which happens from:

	kernel_init()
		smp_init()

The init calls are made a few lines later (still in kernel_init):

		do_basic_setup()
			do_initcalls()

I moved the call radically earlier (before sched_init() in
init/main.c:start_kernel()) just to be sure, but that was
overkill.

Perhaps making the call from do_pre_smp_initcalls() is the
logical place?  Like this (though purists will say that the
extern declaration should be in some header file):

Signed-off-by: Tony Luck <tony.luck@...el.com>

diff --git a/init/main.c b/init/main.c
index 99ce949..0c140ed 100644
--- a/init/main.c
+++ b/init/main.c
@@ -750,7 +750,9 @@ __setup("nosoftlockup", nosoftlockup_setup);
 static void __init do_pre_smp_initcalls(void)
 {
 	extern int spawn_ksoftirqd(void);
+	extern int __cpuinit init_call_single_data(void);
 
+	init_call_single_data();
 	migration_init();
 	spawn_ksoftirqd();
 	if (!nosoftlockup)
diff --git a/kernel/smp.c b/kernel/smp.c
index ab2da5c..df1b651 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -40,7 +40,7 @@ struct call_single_queue {
 static struct call_function_data call_data_fallback;
 static unsigned long call_fallback_used;
 
-static int __cpuinit init_call_single_data(void)
+int __cpuinit init_call_single_data(void)
 {
 	int i;
 
@@ -53,7 +53,6 @@ static int __cpuinit init_call_single_data(void)
 	}
 	return 0;
 }
-core_initcall(init_call_single_data);
 
 /*
  * Insert a previously allocated call_single_data element for execution
--
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