* [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()
[not found] <1338275765-3217-1-git-send-email-yong.zhang0@gmail.com>
@ 2012-05-29 7:16 ` Yong Zhang
2012-06-16 16:32 ` Paul E. McKenney
0 siblings, 1 reply; 6+ messages in thread
From: Yong Zhang @ 2012-05-29 7:16 UTC (permalink / raw)
To: linux-kernel
Cc: axboe, sshtylyov, nikunj, david.daney, peterz, akpm, ralf,
Paul Mackerras, srivatsa.bhat, tglx, paulmck, linuxppc-dev, mingo
From: Yong Zhang <yong.zhang@windriver.com>
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.
Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org
---
arch/powerpc/kernel/smp.c | 2 --
1 files changed, 0 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
index e4cb343..e1417c4 100644
--- a/arch/powerpc/kernel/smp.c
+++ b/arch/powerpc/kernel/smp.c
@@ -571,7 +571,6 @@ void __devinit start_secondary(void *unused)
if (system_state == SYSTEM_RUNNING)
vdso_data->processorCount++;
#endif
- ipi_call_lock();
notify_cpu_starting(cpu);
set_cpu_online(cpu, true);
/* Update sibling maps */
@@ -601,7 +600,6 @@ void __devinit start_secondary(void *unused)
of_node_put(np);
}
of_node_put(l2_cache);
- ipi_call_unlock();
local_irq_enable();
--
1.7.5.4
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()
2012-05-29 7:16 ` [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock() Yong Zhang
@ 2012-06-16 16:32 ` Paul E. McKenney
2012-06-16 17:30 ` Peter Zijlstra
2012-06-18 2:51 ` Yong Zhang
0 siblings, 2 replies; 6+ messages in thread
From: Paul E. McKenney @ 2012-06-16 16:32 UTC (permalink / raw)
To: Yong Zhang
Cc: axboe, nikunj, sshtylyov, david.daney, peterz, linux-kernel, ralf,
akpm, Paul Mackerras, srivatsa.bhat, tglx, linuxppc-dev, mingo
On Tue, May 29, 2012 at 03:16:04PM +0800, Yong Zhang wrote:
> From: Yong Zhang <yong.zhang@windriver.com>
>
> 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.
However, there is an effort to get rid of stop_machine() from the
CPU-down path... So something else will be needed.
Thanx, Paul
> Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: linuxppc-dev@lists.ozlabs.org
> ---
> arch/powerpc/kernel/smp.c | 2 --
> 1 files changed, 0 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index e4cb343..e1417c4 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -571,7 +571,6 @@ void __devinit start_secondary(void *unused)
> if (system_state == SYSTEM_RUNNING)
> vdso_data->processorCount++;
> #endif
> - ipi_call_lock();
> notify_cpu_starting(cpu);
> set_cpu_online(cpu, true);
> /* Update sibling maps */
> @@ -601,7 +600,6 @@ void __devinit start_secondary(void *unused)
> of_node_put(np);
> }
> of_node_put(l2_cache);
> - ipi_call_unlock();
>
> local_irq_enable();
>
> --
> 1.7.5.4
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()
2012-06-16 16:32 ` Paul E. McKenney
@ 2012-06-16 17:30 ` Peter Zijlstra
2012-06-16 20:57 ` Paul E. McKenney
2012-06-18 2:51 ` Yong Zhang
1 sibling, 1 reply; 6+ messages in thread
From: Peter Zijlstra @ 2012-06-16 17:30 UTC (permalink / raw)
To: paulmck
Cc: axboe, sshtylyov, nikunj, david.daney, linux-kernel, ralf, akpm,
Yong Zhang, Paul Mackerras, srivatsa.bhat, tglx, linuxppc-dev,
mingo
On Sat, 2012-06-16 at 09:32 -0700, Paul E. McKenney wrote:
> However, there is an effort to get rid of stop_machine() from the
> CPU-down path... So something else will be needed.=20
Elsewhere in this thread I mentioned we could do a synchronize_sched().
I think that covers most of what stop-machine is doing these days.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()
2012-06-16 17:30 ` Peter Zijlstra
@ 2012-06-16 20:57 ` Paul E. McKenney
0 siblings, 0 replies; 6+ messages in thread
From: Paul E. McKenney @ 2012-06-16 20:57 UTC (permalink / raw)
To: Peter Zijlstra
Cc: axboe, sshtylyov, nikunj, david.daney, linux-kernel, ralf, akpm,
Yong Zhang, Paul Mackerras, srivatsa.bhat, tglx, linuxppc-dev,
mingo
On Sat, Jun 16, 2012 at 07:30:58PM +0200, Peter Zijlstra wrote:
> On Sat, 2012-06-16 at 09:32 -0700, Paul E. McKenney wrote:
> > However, there is an effort to get rid of stop_machine() from the
> > CPU-down path... So something else will be needed.
>
> Elsewhere in this thread I mentioned we could do a synchronize_sched().
> I think that covers most of what stop-machine is doing these days.
Ah, apologies for the noise!
Thanx, Paul
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()
2012-06-16 16:32 ` Paul E. McKenney
2012-06-16 17:30 ` Peter Zijlstra
@ 2012-06-18 2:51 ` Yong Zhang
2012-06-18 17:05 ` Paul E. McKenney
1 sibling, 1 reply; 6+ messages in thread
From: Yong Zhang @ 2012-06-18 2:51 UTC (permalink / raw)
To: Paul E. McKenney
Cc: axboe, nikunj, sshtylyov, david.daney, peterz, linux-kernel, ralf,
akpm, Paul Mackerras, srivatsa.bhat, tglx, linuxppc-dev, mingo
On Sat, Jun 16, 2012 at 09:32:19AM -0700, Paul E. McKenney wrote:
> On Tue, May 29, 2012 at 03:16:04PM +0800, Yong Zhang wrote:
> > From: Yong Zhang <yong.zhang@windriver.com>
> >
> > 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.
>
> However, there is an effort to get rid of stop_machine() from the
> CPU-down path... So something else will be needed.
Yeah. So Thomas changed the commit log like below:
[
ipi_call_lock/unlock() lock resp. unlock call_function.lock. This lock
protects only the call_function data structure itself, but it's
completely unrelated to cpu_online_mask. The mask to which the IPIs
are sent is calculated before call_function.lock is taken in
smp_call_function_many(), so the locking around set_cpu_online() is
pointless and can be removed.
[ tglx: Massaged changelog ]
]
in tip/smp/hotplug.
Thanks,
Yong
>
> Thanx, Paul
>
> > Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> > Cc: Paul Mackerras <paulus@samba.org>
> > Cc: linuxppc-dev@lists.ozlabs.org
> > ---
> > arch/powerpc/kernel/smp.c | 2 --
> > 1 files changed, 0 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> > index e4cb343..e1417c4 100644
> > --- a/arch/powerpc/kernel/smp.c
> > +++ b/arch/powerpc/kernel/smp.c
> > @@ -571,7 +571,6 @@ void __devinit start_secondary(void *unused)
> > if (system_state == SYSTEM_RUNNING)
> > vdso_data->processorCount++;
> > #endif
> > - ipi_call_lock();
> > notify_cpu_starting(cpu);
> > set_cpu_online(cpu, true);
> > /* Update sibling maps */
> > @@ -601,7 +600,6 @@ void __devinit start_secondary(void *unused)
> > of_node_put(np);
> > }
> > of_node_put(l2_cache);
> > - ipi_call_unlock();
> >
> > local_irq_enable();
> >
> > --
> > 1.7.5.4
> >
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
Only stand for myself
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()
2012-06-18 2:51 ` Yong Zhang
@ 2012-06-18 17:05 ` Paul E. McKenney
0 siblings, 0 replies; 6+ messages in thread
From: Paul E. McKenney @ 2012-06-18 17:05 UTC (permalink / raw)
To: Yong Zhang
Cc: axboe, nikunj, sshtylyov, david.daney, peterz, linux-kernel, ralf,
akpm, Paul Mackerras, srivatsa.bhat, tglx, linuxppc-dev, mingo
On Mon, Jun 18, 2012 at 10:51:59AM +0800, Yong Zhang wrote:
> On Sat, Jun 16, 2012 at 09:32:19AM -0700, Paul E. McKenney wrote:
> > On Tue, May 29, 2012 at 03:16:04PM +0800, Yong Zhang wrote:
> > > From: Yong Zhang <yong.zhang@windriver.com>
> > >
> > > 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.
> >
> > However, there is an effort to get rid of stop_machine() from the
> > CPU-down path... So something else will be needed.
>
> Yeah. So Thomas changed the commit log like below:
> [
> ipi_call_lock/unlock() lock resp. unlock call_function.lock. This lock
> protects only the call_function data structure itself, but it's
> completely unrelated to cpu_online_mask. The mask to which the IPIs
> are sent is calculated before call_function.lock is taken in
> smp_call_function_many(), so the locking around set_cpu_online() is
> pointless and can be removed.
>
> [ tglx: Massaged changelog ]
> ]
>
> in tip/smp/hotplug.
Got it, thank you!
Thanx, Paul
> Thanks,
> Yong
>
> >
> > Thanx, Paul
> >
> > > Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
> > > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> > > Cc: Paul Mackerras <paulus@samba.org>
> > > Cc: linuxppc-dev@lists.ozlabs.org
> > > ---
> > > arch/powerpc/kernel/smp.c | 2 --
> > > 1 files changed, 0 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> > > index e4cb343..e1417c4 100644
> > > --- a/arch/powerpc/kernel/smp.c
> > > +++ b/arch/powerpc/kernel/smp.c
> > > @@ -571,7 +571,6 @@ void __devinit start_secondary(void *unused)
> > > if (system_state == SYSTEM_RUNNING)
> > > vdso_data->processorCount++;
> > > #endif
> > > - ipi_call_lock();
> > > notify_cpu_starting(cpu);
> > > set_cpu_online(cpu, true);
> > > /* Update sibling maps */
> > > @@ -601,7 +600,6 @@ void __devinit start_secondary(void *unused)
> > > of_node_put(np);
> > > }
> > > of_node_put(l2_cache);
> > > - ipi_call_unlock();
> > >
> > > local_irq_enable();
> > >
> > > --
> > > 1.7.5.4
> > >
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.tux.org/lkml/
>
> --
> Only stand for myself
>
^ permalink raw reply [flat|nested] 6+ messages in thread
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[not found] <1338275765-3217-1-git-send-email-yong.zhang0@gmail.com>
2012-05-29 7:16 ` [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock() Yong Zhang
2012-06-16 16:32 ` Paul E. McKenney
2012-06-16 17:30 ` Peter Zijlstra
2012-06-16 20:57 ` Paul E. McKenney
2012-06-18 2:51 ` Yong Zhang
2012-06-18 17:05 ` Paul E. McKenney
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