linux-kernel - Re: [PATCH 5/5] s390: Use common fork_idle_from

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Date:	Wed, 7 Mar 2012 08:00:00 +0100
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Venkatesh Pallipadi <venki@...gle.com>
Cc:	Suresh Siddha <suresh.b.siddha@...el.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Aaron Durbin <adurbin@...gle.com>,
	Paul Turner <pjt@...gle.com>,
	Yong Zhang <yong.zhang0@...il.com>,
	linux-kernel@...r.kernel.org, Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 5/5] s390: Use common fork_idle_from_wq in smpboot

On Tue, Mar 06, 2012 at 01:41:14PM -0800, Venkatesh Pallipadi wrote:
> Cleanup. Instead of reimplementing fork_idle on wq and idle task caching,
> use fork_idle_from_wq().
> 
> Signed-off-by: Venkatesh Pallipadi <venki@...gle.com>
> ---
>  arch/s390/kernel/smp.c |   38 +++++---------------------------------
>  1 files changed, 5 insertions(+), 33 deletions(-)

Your patch won't apply on linux-next because of rather large code changes.
Anyway see below a patch that applies cleanly (and works) on s390.
Thanks for cleaning this up!

Acked-by: Heiko Carstens <heiko.carstens@...ibm.com>

---
 arch/s390/kernel/smp.c |   36 +++++-------------------------------
 1 file changed, 5 insertions(+), 31 deletions(-)

--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -83,7 +83,6 @@ enum {
 
 struct pcpu {
 	struct cpu cpu;
-	struct task_struct *idle;	/* idle process for the cpu */
 	struct _lowcore *lowcore;	/* lowcore page(s) for the cpu */
 	unsigned long async_stack;	/* async stack for the cpu */
 	unsigned long panic_stack;	/* panic stack for the cpu */
@@ -724,26 +723,10 @@ static void __cpuinit smp_start_secondar
 	cpu_idle();
 }
 
-struct create_idle {
-	struct work_struct work;
-	struct task_struct *idle;
-	struct completion done;
-	int cpu;
-};
-
-static void __cpuinit smp_fork_idle(struct work_struct *work)
-{
-	struct create_idle *c_idle;
-
-	c_idle = container_of(work, struct create_idle, work);
-	c_idle->idle = fork_idle(c_idle->cpu);
-	complete(&c_idle->done);
-}
-
 /* Upping and downing of CPUs */
 int __cpuinit __cpu_up(unsigned int cpu)
 {
-	struct create_idle c_idle;
+	struct task_struct *idle;
 	struct pcpu *pcpu;
 	int rc;
 
@@ -753,22 +736,14 @@ int __cpuinit __cpu_up(unsigned int cpu)
 	if (pcpu_sigp_retry(pcpu, sigp_initial_cpu_reset, 0) !=
 	    sigp_order_code_accepted)
 		return -EIO;
-	if (!pcpu->idle) {
-		c_idle.done = COMPLETION_INITIALIZER_ONSTACK(c_idle.done);
-		INIT_WORK_ONSTACK(&c_idle.work, smp_fork_idle);
-		c_idle.cpu = cpu;
-		schedule_work(&c_idle.work);
-		wait_for_completion(&c_idle.done);
-		if (IS_ERR(c_idle.idle))
-			return PTR_ERR(c_idle.idle);
-		pcpu->idle = c_idle.idle;
-	}
-	init_idle(pcpu->idle, cpu);
+	idle = fork_idle_from_wq(cpu);
+	if (IS_ERR(idle))
+		return PTR_ERR(idle);
 	rc = pcpu_alloc_lowcore(pcpu, cpu);
 	if (rc)
 		return rc;
 	pcpu_prepare_secondary(pcpu, cpu);
-	pcpu_attach_task(pcpu, pcpu->idle);
+	pcpu_attach_task(pcpu, idle);
 	pcpu_start_fn(pcpu, smp_start_secondary, NULL);
 	while (!cpu_online(cpu))
 		cpu_relax();
@@ -855,7 +830,6 @@ void __init smp_prepare_boot_cpu(void)
 	struct pcpu *pcpu = pcpu_devices;
 
 	boot_cpu_address = stap();
-	pcpu->idle = current;
 	pcpu->state = CPU_STATE_CONFIGURED;
 	pcpu->address = boot_cpu_address;
 	pcpu->lowcore = (struct _lowcore *)(unsigned long) store_prefix();

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