linux-kernel - [RFC PATCH 00/10] Cleanup ipi_call_lock[_irq]()/ipi_call_unlock[

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Date:	Tue, 29 May 2012 15:15:55 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	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,
	srivatsa.bhat@...ux.vnet.ibm.com
Subject: [RFC PATCH 00/10] Cleanup ipi_call_lock[_irq]()/ipi_call_unlock[_irq]()

As discussed with Srivatsa [1], it seems there is no need to keep
ipi_call_[un]lock_irq() when cpu bring-up/down. Because:

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.

In short it's more likely that keeping ipi_call_[un]lock() is leftover
before we introduce generic smp helper. This patchset is just to clean
things up.

[1] http://marc.info/?l=linux-kernel&m=133766786814484&w=2

Yong Zhang (10):
  hexagon: smp: remove call to ipi_call_lock()/ipi_call_unlock()
  mn10300: smp: remove call to ipi_call_lock()/ipi_call_unlock()
  parisc: smp: remove call to ipi_call_lock()/ipi_call_unlock()
  S390: smp: remove call to ipi_call_lock()/ipi_call_unlock()
  tile: smp: remove call to ipi_call_lock()/ipi_call_unlock()
  x86: smp: remove call to ipi_call_lock()/ipi_call_unlock()
  ia64: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()
  SPARC: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()
  POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()
  smp: remove ipi_call_lock[_irq]()/ipi_call_unlock[_irq]()

 arch/hexagon/kernel/smp.c  |    2 --
 arch/ia64/kernel/smpboot.c |    2 --
 arch/mn10300/kernel/smp.c  |    2 --
 arch/parisc/kernel/smp.c   |    2 --
 arch/powerpc/kernel/smp.c  |    2 --
 arch/s390/kernel/smp.c     |    2 --
 arch/sparc/kernel/smp_64.c |    6 ++----
 arch/tile/kernel/smpboot.c |   10 ----------
 arch/x86/kernel/smpboot.c  |    9 ---------
 arch/x86/xen/smp.c         |    2 --
 include/linux/smp.h        |    4 ----
 kernel/smp.c               |   20 --------------------
 12 files changed, 2 insertions(+), 61 deletions(-)

-- 
1.7.5.4

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