* [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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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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