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SubjectRe: [RFC PATCH 00/10] Cleanup ipi_call_lock[_irq]()/ipi_call_unlock[_irq]()
On Tue, May 29, 2012 at 03:15:55PM +0800, Yong Zhang wrote:
> 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.

This series gets rid of the call_function lockdep splat I was seeing,
very good!

Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

> [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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