linux-kernel - Re: [GIT PULL] percpu consistent-ops changes for v3.18-rc1

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Date:	Wed, 15 Oct 2014 08:38:22 +1100
From:	Stephen Rothwell <sfr@...b.auug.org.au>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
	Christoph Lameter <cl@...ux-foundation.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [GIT PULL] percpu consistent-ops changes for v3.18-rc1

Hi Linus,

On Tue, 14 Oct 2014 09:07:52 -0400 Tejun Heo <tj@...nel.org> wrote:
>
> 2. arch/s390/kernel/vtime.c
> 
> b5f87f15e200 ("s390/idle: consolidate idle functions and definitions")
> removes two functions which contained percpu accesses.
> 
>   <<<<<<< HEAD
>   =======
>   void __kprobes vtime_stop_cpu(void)
>   {
> 	  struct s390_idle_data *idle = this_cpu_ptr(&s390_idle);
> 	  unsigned long long idle_time;
> 	  unsigned long psw_mask;
> 
> 	  trace_hardirqs_on();
> 
> 	  /* Wait for external, I/O or machine check interrupt. */
> 	  psw_mask = PSW_KERNEL_BITS | PSW_MASK_WAIT | PSW_MASK_DAT |
> 		  PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
> 	  idle->nohz_delay = 0;
> 
> 	  /* Call the assembler magic in entry.S */
> 	  psw_idle(idle, psw_mask);
> 
> 	  /* Account time spent with enabled wait psw loaded as idle time. */
> 	  idle->sequence++;
> 	  smp_wmb();
> 	  idle_time = idle->clock_idle_exit - idle->clock_idle_enter;
> 	  idle->clock_idle_enter = idle->clock_idle_exit = 0ULL;
> 	  idle->idle_time += idle_time;
> 	  idle->idle_count++;
> 	  account_idle_time(idle_time);
> 	  smp_wmb();
> 	  idle->sequence++;
>   }
> 
>   cputime64_t s390_get_idle_time(int cpu)
>   {
> 	  struct s390_idle_data *idle = &per_cpu(s390_idle, cpu);
> 	  unsigned long long now, idle_enter, idle_exit;
> 	  unsigned int sequence;
> 
> 	  do {
> 		  now = get_tod_clock();
> 		  sequence = ACCESS_ONCE(idle->sequence);
> 		  idle_enter = ACCESS_ONCE(idle->clock_idle_enter);
> 		  idle_exit = ACCESS_ONCE(idle->clock_idle_exit);
> 	  } while ((sequence & 1) || (ACCESS_ONCE(idle->sequence) != sequence));
> 	  return idle_enter ? ((idle_exit ?: now) - idle_enter) : 0;
>   }
> 
>   >>>>>>> 513d1a2884a49654f368b5fa25ef186e976bdada
> 
> The conflicting code can be removed.

This actually moved some of the code into a new file and so, for
completeness, I have been carrying the following merge fix patch (which
you could include in the merge - but I am not sure if it matters if the
old accessors are still around):

From: Stephen Rothwell <sfr@...b.auug.org.au>
Date: Tue, 7 Oct 2014 16:44:38 +1100
Subject: [PATCH] s390: fixup for Replace __get_cpu_var uses

Signed-off-by: Stephen Rothwell <sfr@...b.auug.org.au>
---
 arch/s390/kernel/idle.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/kernel/idle.c b/arch/s390/kernel/idle.c
index c75fbae1e37e..9d19a91dc6a6 100644
--- a/arch/s390/kernel/idle.c
+++ b/arch/s390/kernel/idle.c
@@ -20,7 +20,7 @@ static DEFINE_PER_CPU(struct s390_idle_data, s390_idle);
 
 void __kprobes enabled_wait(void)
 {
-	struct s390_idle_data *idle = &__get_cpu_var(s390_idle);
+	struct s390_idle_data *idle = this_cpu_ptr(&s390_idle);
 	unsigned long long idle_time;
 	unsigned long psw_mask;
 
-- 
2.1.1

-- 
Cheers,
Stephen Rothwell                    sfr@...b.auug.org.au

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