linux-kernel - [UPDATED] [RFC PATCH 08/10] SPARC: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock

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Date:	Tue, 29 May 2012 16:27:33 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, ralf@...ux-mips.org,
	sshtylyov@...sta.com, david.daney@...ium.com,
	nikunj@...ux.vnet.ibm.com, paulmck@...ux.vnet.ibm.com,
	axboe@...nel.dk, mingo@...nel.org, tglx@...utronix.de,
	peterz@...radead.org, akpm@...ux-foundation.org,
	"David S. Miller" <davem@...emloft.net>, sparclinux@...r.kernel.org
Subject: [UPDATED] [RFC PATCH 08/10] SPARC: smp: remove call to
 ipi_call_lock_irq()/ipi_call_unlock_irq()

On Tue, May 29, 2012 at 01:31:54PM +0530, Srivatsa S. Bhat wrote:
> This looks odd. IRQs must not have been enabled at this point.
> Just remove the call to local_irq_enable() that is found a few lines above
> this line and then you won't have to add this call to local_irq_disable().

Yeah, have thought about it. But because I was not sure there is
special need to enalbe irq that early (don't know much about sparc),
I decided to make minor change :)

Since we have gotten confirmation from David, I'm sending out the
new version. Please check it.

Thanks,
Yong

---
From: Yong Zhang <yong.zhang@...driver.com>
Date: Tue, 29 May 2012 12:56:08 +0800
Subject: [UPDATED] [RFC PATCH 8/10] SPARC: smp: remove call to
 ipi_call_lock_irq()/ipi_call_unlock_irq()

1) call_function.lock used in smp_call_function_many() is just to protect
   call_function.queue and &data->refs, cpu_online_mask is outside of the
   lock. And it's not necessary to protect cpu_online_mask,
   because data->cpumask is pre-calculate and even if a cpu is brougt up
   when calling arch_send_call_function_ipi_mask(), it's harmless because
   validation test in generic_smp_call_function_interrupt() will take care
   of it.

2) For cpu down issue, stop_machine() will guarantee that no concurrent
   smp_call_fuction() is processing.

And also delay irq enable to after set_cpu_online().

Signed-off-by: Yong Zhang <yong.zhang0@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: sparclinux@...r.kernel.org
---
 arch/sparc/kernel/smp_64.c |    7 +------
 1 files changed, 1 insertions(+), 6 deletions(-)

diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index f591598..781bcb1 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -103,8 +103,6 @@ void __cpuinit smp_callin(void)
 	if (cheetah_pcache_forced_on)
 		cheetah_enable_pcache();
 
-	local_irq_enable();
-
 	callin_flag = 1;
 	__asm__ __volatile__("membar #Sync\n\t"
 			     "flush  %%g6" : : : "memory");
@@ -124,9 +122,8 @@ void __cpuinit smp_callin(void)
 	while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
 		rmb();
 
-	ipi_call_lock_irq();
 	set_cpu_online(cpuid, true);
-	ipi_call_unlock_irq();
+	local_irq_enable();
 
 	/* idle thread is expected to have preempt disabled */
 	preempt_disable();
@@ -1308,9 +1305,7 @@ int __cpu_disable(void)
 	mdelay(1);
 	local_irq_disable();
 
-	ipi_call_lock();
 	set_cpu_online(cpu, false);
-	ipi_call_unlock();
 
 	cpu_map_rebuild();
 
-- 
1.7.5.4

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