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

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

[Yong Zhang]

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

[RFC PATCH 01/10] hexagon: smp: remove call to ipi_call_lock()/ipi_call_unlock()

[Yong Zhang]

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: Richard Kuo <rkuo@codeaurora.org>
Cc: linux-hexagon@vger.kernel.org
---
 arch/hexagon/kernel/smp.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/hexagon/kernel/smp.c b/arch/hexagon/kernel/smp.c
index f726462..149fbef 100644
--- a/arch/hexagon/kernel/smp.c
+++ b/arch/hexagon/kernel/smp.c
@@ -180,9 +180,7 @@ void __cpuinit start_secondary(void)
 
 	notify_cpu_starting(cpu);
 
-	ipi_call_lock();
 	set_cpu_online(cpu, true);
-	ipi_call_unlock();
 
 	local_irq_enable();
 
-- 
1.7.5.4

[RFC PATCH 02/10] mn10300: smp: remove call to ipi_call_lock()/ipi_call_unlock()

[Yong Zhang]

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: David Howells <dhowells@redhat.com>
Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
Cc: linux-am33-list@redhat.com
---
 arch/mn10300/kernel/smp.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/mn10300/kernel/smp.c b/arch/mn10300/kernel/smp.c
index 090d35d..e62c223 100644
--- a/arch/mn10300/kernel/smp.c
+++ b/arch/mn10300/kernel/smp.c
@@ -876,9 +876,7 @@ static void __init smp_online(void)
 
 	notify_cpu_starting(cpu);
 
-	ipi_call_lock();
 	set_cpu_online(cpu, true);
-	ipi_call_unlock();
 
 	local_irq_enable();
 }
-- 
1.7.5.4

[RFC PATCH 03/10] parisc: smp: remove call to ipi_call_lock()/ipi_call_unlock()

[Yong Zhang]

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: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-parisc@vger.kernel.org
---
 arch/parisc/kernel/smp.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
index a47828d..6266730 100644
--- a/arch/parisc/kernel/smp.c
+++ b/arch/parisc/kernel/smp.c
@@ -300,9 +300,7 @@ smp_cpu_init(int cpunum)
 
 	notify_cpu_starting(cpunum);
 
-	ipi_call_lock();
 	set_cpu_online(cpunum, true);
-	ipi_call_unlock();
 
 	/* Initialise the idle task for this CPU */
 	atomic_inc(&init_mm.mm_count);
-- 
1.7.5.4

[RFC PATCH 04/10] S390: smp: remove call to ipi_call_lock()/ipi_call_unlock()

[Yong Zhang]

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: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux390@de.ibm.com
Cc: linux-s390@vger.kernel.org
---
 arch/s390/kernel/smp.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 647ba94..14c8a08 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -716,9 +716,7 @@ static void __cpuinit smp_start_secondary(void *cpuvoid)
 	init_cpu_vtimer();
 	pfault_init();
 	notify_cpu_starting(smp_processor_id());
-	ipi_call_lock();
 	set_cpu_online(smp_processor_id(), true);
-	ipi_call_unlock();
 	local_irq_enable();
 	/* cpu_idle will call schedule for us */
 	cpu_idle();
-- 
1.7.5.4

[RFC PATCH 05/10] tile: smp: remove call to ipi_call_lock()/ipi_call_unlock()

[Yong Zhang]

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: Chris Metcalf <cmetcalf@tilera.com>
---
 arch/tile/kernel/smpboot.c |   10 ----------
 1 files changed, 0 insertions(+), 10 deletions(-)

diff --git a/arch/tile/kernel/smpboot.c b/arch/tile/kernel/smpboot.c
index 84873fb..e686c5a 100644
--- a/arch/tile/kernel/smpboot.c
+++ b/arch/tile/kernel/smpboot.c
@@ -198,17 +198,7 @@ void __cpuinit online_secondary(void)
 
 	notify_cpu_starting(smp_processor_id());
 
-	/*
-	 * We need to hold call_lock, so there is no inconsistency
-	 * between the time smp_call_function() determines number of
-	 * IPI recipients, and the time when the determination is made
-	 * for which cpus receive the IPI. Holding this
-	 * lock helps us to not include this cpu in a currently in progress
-	 * smp_call_function().
-	 */
-	ipi_call_lock();
 	set_cpu_online(smp_processor_id(), 1);
-	ipi_call_unlock();
 	__get_cpu_var(cpu_state) = CPU_ONLINE;
 
 	/* Set up tile-specific state for this cpu. */
-- 
1.7.5.4

[RFC PATCH 06/10] x86: smp: remove call to ipi_call_lock()/ipi_call_unlock()

[Yong Zhang]

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: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
---
 arch/x86/kernel/smpboot.c |    9 ---------
 arch/x86/xen/smp.c        |    2 --
 2 files changed, 0 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 433529e..bfbe30e 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -253,22 +253,13 @@ notrace static void __cpuinit start_secondary(void *unused)
 	check_tsc_sync_target();
 
 	/*
-	 * We need to hold call_lock, so there is no inconsistency
-	 * between the time smp_call_function() determines number of
-	 * IPI recipients, and the time when the determination is made
-	 * for which cpus receive the IPI. Holding this
-	 * lock helps us to not include this cpu in a currently in progress
-	 * smp_call_function().
-	 *
 	 * We need to hold vector_lock so there the set of online cpus
 	 * does not change while we are assigning vectors to cpus.  Holding
 	 * this lock ensures we don't half assign or remove an irq from a cpu.
 	 */
-	ipi_call_lock();
 	lock_vector_lock();
 	set_cpu_online(smp_processor_id(), true);
 	unlock_vector_lock();
-	ipi_call_unlock();
 	per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
 	x86_platform.nmi_init();
 
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index afb250d..f58dca7 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -80,9 +80,7 @@ static void __cpuinit cpu_bringup(void)
 
 	notify_cpu_starting(cpu);
 
-	ipi_call_lock();
 	set_cpu_online(cpu, true);
-	ipi_call_unlock();
 
 	this_cpu_write(cpu_state, CPU_ONLINE);
 
-- 
1.7.5.4

[RFC PATCH 07/10] ia64: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()

[Yong Zhang]

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: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: linux-ia64@vger.kernel.org
---
 arch/ia64/kernel/smpboot.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/ia64/kernel/smpboot.c b/arch/ia64/kernel/smpboot.c
index 1113b8a..963d2db 100644
--- a/arch/ia64/kernel/smpboot.c
+++ b/arch/ia64/kernel/smpboot.c
@@ -382,7 +382,6 @@ smp_callin (void)
 	set_numa_node(cpu_to_node_map[cpuid]);
 	set_numa_mem(local_memory_node(cpu_to_node_map[cpuid]));
 
-	ipi_call_lock_irq();
 	spin_lock(&vector_lock);
 	/* Setup the per cpu irq handling data structures */
 	__setup_vector_irq(cpuid);
@@ -390,7 +389,6 @@ smp_callin (void)
 	set_cpu_online(cpuid, true);
 	per_cpu(cpu_state, cpuid) = CPU_ONLINE;
 	spin_unlock(&vector_lock);
-	ipi_call_unlock_irq();
 
 	smp_setup_percpu_timer();
 
-- 
1.7.5.4

[PATCH 08/10] SPARC: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()

[Yong Zhang]

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: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
---
 arch/sparc/kernel/smp_64.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index f591598..60e745c 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -124,9 +124,9 @@ void __cpuinit smp_callin(void)
 	while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
 		rmb();
 
-	ipi_call_lock_irq();
+	local_irq_disable();
 	set_cpu_online(cpuid, true);
-	ipi_call_unlock_irq();
+	local_irq_enable();
 
 	/* idle thread is expected to have preempt disabled */
 	preempt_disable();
@@ -1308,9 +1308,7 @@ int __cpu_disable(void)
 	mdelay(1);
 	local_irq_disable();
 
-	ipi_call_lock();
 	set_cpu_online(cpu, false);
-	ipi_call_unlock();
 
 	cpu_map_rebuild();
 
-- 
1.7.5.4

[RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()

[Yong Zhang]

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

[RFC PATCH 10/10] smp: remove ipi_call_lock[_irq]()/ipi_call_unlock[_irq]()

[Yong Zhang]

From: Yong Zhang <yong.zhang@windriver.com>

There is no user of those APIs anymore, just remove it.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/smp.h |    4 ----
 kernel/smp.c        |   20 --------------------
 2 files changed, 0 insertions(+), 24 deletions(-)

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 717fb74..a34d4f1 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -90,10 +90,6 @@ void kick_all_cpus_sync(void);
 void __init call_function_init(void);
 void generic_smp_call_function_single_interrupt(void);
 void generic_smp_call_function_interrupt(void);
-void ipi_call_lock(void);
-void ipi_call_unlock(void);
-void ipi_call_lock_irq(void);
-void ipi_call_unlock_irq(void);
 #else
 static inline void call_function_init(void) { }
 #endif
diff --git a/kernel/smp.c b/kernel/smp.c
index d0ae5b2..29dd40a 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -581,26 +581,6 @@ int smp_call_function(smp_call_func_t func, void *info, int wait)
 	return 0;
 }
 EXPORT_SYMBOL(smp_call_function);
-
-void ipi_call_lock(void)
-{
-	raw_spin_lock(&call_function.lock);
-}
-
-void ipi_call_unlock(void)
-{
-	raw_spin_unlock(&call_function.lock);
-}
-
-void ipi_call_lock_irq(void)
-{
-	raw_spin_lock_irq(&call_function.lock);
-}
-
-void ipi_call_unlock_irq(void)
-{
-	raw_spin_unlock_irq(&call_function.lock);
-}
 #endif /* USE_GENERIC_SMP_HELPERS */
 
 /* Setup configured maximum number of CPUs to activate */
-- 
1.7.5.4

Re: [PATCH 08/10] SPARC: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()

[Srivatsa S. Bhat]

On 05/29/2012 12:46 PM, 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.
> 
> Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: sparclinux@vger.kernel.org
> ---
>  arch/sparc/kernel/smp_64.c |    6 ++----
>  1 files changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
> index f591598..60e745c 100644
> --- a/arch/sparc/kernel/smp_64.c
> +++ b/arch/sparc/kernel/smp_64.c
> @@ -124,9 +124,9 @@ void __cpuinit smp_callin(void)
>  	while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
>  		rmb();
> 
> -	ipi_call_lock_irq();
> +	local_irq_disable();


This looks odd. IRQs must not have been enabled at this point.
Just remove the call to local_irq_enable() that is found a few lines above
this line and then you won't have to add this call to local_irq_disable().

>  	set_cpu_online(cpuid, true);
> -	ipi_call_unlock_irq();
> +	local_irq_enable();
> 

>  	/* idle thread is expected to have preempt disabled */

>  	preempt_disable();
> @@ -1308,9 +1308,7 @@ int __cpu_disable(void)
>  	mdelay(1);
>  	local_irq_disable();
> 
> -	ipi_call_lock();
>  	set_cpu_online(cpu, false);
> -	ipi_call_unlock();
> 
>  	cpu_map_rebuild();
> 



Regards,
Srivatsa S. Bhat

Re: [RFC PATCH 00/10] Cleanup ipi_call_lock[_irq]()/ipi_call_unlock[_irq]()

[Srivatsa S. Bhat]

On 05/29/2012 12:45 PM, 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.
> 
> [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]()
>


All patches except the sparc one look good.
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

Regards,
Srivatsa S. Bhat

Re: [PATCH 08/10] SPARC: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()

[David Miller]

From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Date: Tue, 29 May 2012 13:31:54 +0530

> On 05/29/2012 12:46 PM, 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.
>> 
>> Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
>> Cc: "David S. Miller" <davem@davemloft.net>
>> Cc: sparclinux@vger.kernel.org
>> ---
>>  arch/sparc/kernel/smp_64.c |    6 ++----
>>  1 files changed, 2 insertions(+), 4 deletions(-)
>> 
>> diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
>> index f591598..60e745c 100644
>> --- a/arch/sparc/kernel/smp_64.c
>> +++ b/arch/sparc/kernel/smp_64.c
>> @@ -124,9 +124,9 @@ void __cpuinit smp_callin(void)
>>  	while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
>>  		rmb();
>> 
>> -	ipi_call_lock_irq();
>> +	local_irq_disable();
> 
> 
> This looks odd. IRQs must not have been enabled at this point.
> Just remove the call to local_irq_enable() that is found a few lines above
> this line and then you won't have to add this call to local_irq_disable().

Agreed.

[UPDATED] [RFC PATCH 08/10] SPARC: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()

[Yong Zhang]

On Tue, May 29, 2012 at 01:31:54PM +0530, Srivatsa S. Bhat wrote:
> This looks odd. IRQs must not have been enabled at this point.
> Just remove the call to local_irq_enable() that is found a few lines above
> this line and then you won't have to add this call to local_irq_disable().

Yeah, have thought about it. But because I was not sure there is
special need to enalbe irq that early (don't know much about sparc),
I decided to make minor change :)

Since we have gotten confirmation from David, I'm sending out the
new version. Please check it.

Thanks,
Yong

---
From: Yong Zhang <yong.zhang@windriver.com>
Date: Tue, 29 May 2012 12:56:08 +0800
Subject: [UPDATED] [RFC PATCH 8/10] SPARC: smp: remove call to
 ipi_call_lock_irq()/ipi_call_unlock_irq()

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.

And also delay irq enable to after set_cpu_online().

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
---
 arch/sparc/kernel/smp_64.c |    7 +------
 1 files changed, 1 insertions(+), 6 deletions(-)

diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index f591598..781bcb1 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -103,8 +103,6 @@ void __cpuinit smp_callin(void)
 	if (cheetah_pcache_forced_on)
 		cheetah_enable_pcache();
 
-	local_irq_enable();
-
 	callin_flag = 1;
 	__asm__ __volatile__("membar #Sync\n\t"
 			     "flush  %%g6" : : : "memory");
@@ -124,9 +122,8 @@ void __cpuinit smp_callin(void)
 	while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
 		rmb();
 
-	ipi_call_lock_irq();
 	set_cpu_online(cpuid, true);
-	ipi_call_unlock_irq();
+	local_irq_enable();
 
 	/* idle thread is expected to have preempt disabled */
 	preempt_disable();
@@ -1308,9 +1305,7 @@ int __cpu_disable(void)
 	mdelay(1);
 	local_irq_disable();
 
-	ipi_call_lock();
 	set_cpu_online(cpu, false);
-	ipi_call_unlock();
 
 	cpu_map_rebuild();
 
-- 
1.7.5.4

Re: [RFC PATCH 00/10] Cleanup ipi_call_lock[_irq]()/ipi_call_unlock[_irq]()

[Peter Zijlstra]

On Tue, 2012-05-29 at 15:15 +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. 

But that lock was only taken around setting a cpu online, so the offline
case is pretty much irrelevant for these patches, right?

That said, is there an alternative to stop_machine on the down side?

I guess flipping the cpu offline and then doing synchronize_sched()
should suffice.

Re: [UPDATED] [RFC PATCH 08/10] SPARC: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()

[Srivatsa S. Bhat]

On 05/29/2012 01:57 PM, Yong Zhang wrote:

> On Tue, May 29, 2012 at 01:31:54PM +0530, Srivatsa S. Bhat wrote:
>> This looks odd. IRQs must not have been enabled at this point.
>> Just remove the call to local_irq_enable() that is found a few lines above
>> this line and then you won't have to add this call to local_irq_disable().
> 
> Yeah, have thought about it. But because I was not sure there is
> special need to enalbe irq that early (don't know much about sparc),
> I decided to make minor change :)
> 
> Since we have gotten confirmation from David, I'm sending out the
> new version. Please check it.
> 
> Thanks,
> Yong
> 
> ---
> From: Yong Zhang <yong.zhang@windriver.com>
> Date: Tue, 29 May 2012 12:56:08 +0800
> Subject: [UPDATED] [RFC PATCH 8/10] SPARC: smp: remove call to
>  ipi_call_lock_irq()/ipi_call_unlock_irq()
> 
> 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.
> 
> And also delay irq enable to after set_cpu_online().
> 
> Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: sparclinux@vger.kernel.org

> ---


Looks good.
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>

>  arch/sparc/kernel/smp_64.c |    7 +------
>  1 files changed, 1 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
> index f591598..781bcb1 100644
> --- a/arch/sparc/kernel/smp_64.c
> +++ b/arch/sparc/kernel/smp_64.c
> @@ -103,8 +103,6 @@ void __cpuinit smp_callin(void)
>  	if (cheetah_pcache_forced_on)
>  		cheetah_enable_pcache();
> 
> -	local_irq_enable();
> -
>  	callin_flag = 1;
>  	__asm__ __volatile__("membar #Sync\n\t"
>  			     "flush  %%g6" : : : "memory");
> @@ -124,9 +122,8 @@ void __cpuinit smp_callin(void)
>  	while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
>  		rmb();
> 
> -	ipi_call_lock_irq();
>  	set_cpu_online(cpuid, true);
> -	ipi_call_unlock_irq();
> +	local_irq_enable();
> 
>  	/* idle thread is expected to have preempt disabled */
>  	preempt_disable();
> @@ -1308,9 +1305,7 @@ int __cpu_disable(void)
>  	mdelay(1);
>  	local_irq_disable();
> 
> -	ipi_call_lock();
>  	set_cpu_online(cpu, false);
> -	ipi_call_unlock();
> 
>  	cpu_map_rebuild();
> 

Re: [RFC PATCH 00/10] Cleanup ipi_call_lock[_irq]()/ipi_call_unlock[_irq]()

[Peter Zijlstra]

On Tue, 2012-05-29 at 10:28 +0200, Peter Zijlstra wrote:
> On Tue, 2012-05-29 at 15:15 +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. 
> 
> But that lock was only taken around setting a cpu online, so the offline
> case is pretty much irrelevant for these patches, right?

Ah, I see, some archs also did it on offline.

> That said, is there an alternative to stop_machine on the down side?
> 
> I guess flipping the cpu offline and then doing synchronize_sched()
> should suffice.

Re: [RFC PATCH 00/10] Cleanup ipi_call_lock[_irq]()/ipi_call_unlock[_irq]()

[Srivatsa S. Bhat]

On 05/29/2012 01:58 PM, Peter Zijlstra wrote:


> That said, is there an alternative to stop_machine on the down side?
> 
> I guess flipping the cpu offline and then doing synchronize_sched()
> should suffice.
> 


Yes I think so. Even Paul McKenney had suggested this.

Regards,
Srivatsa S. Bhat

Re: [UPDATED] [RFC PATCH 08/10] SPARC: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()

[David Miller]

From: Yong Zhang <yong.zhang0@gmail.com>
Date: Tue, 29 May 2012 16:27:33 +0800

> From: Yong Zhang <yong.zhang@windriver.com>
> Date: Tue, 29 May 2012 12:56:08 +0800
> Subject: [UPDATED] [RFC PATCH 8/10] SPARC: smp: remove call to
>  ipi_call_lock_irq()/ipi_call_unlock_irq()
> 
> 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.
> 
> And also delay irq enable to after set_cpu_online().
> 
> Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>

Acked-by: David S. Miller <davem@davemloft.net>

[tip:smp/hotplug] hexagon: SMP: Remove call to ipi_call_lock()/ ipi_call_unlock()

[tip-bot for Yong Zhang]

Commit-ID:  4ee0444bebf3d0399c93841d98826ade193e6330
Gitweb:     http://git.kernel.org/tip/4ee0444bebf3d0399c93841d98826ade193e6330
Author:     Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Tue, 29 May 2012 15:15:56 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 5 Jun 2012 17:27:11 +0200

hexagon: SMP: Remove call to ipi_call_lock()/ipi_call_unlock()

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 ]

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: linux-hexagon@vger.kernel.org
Link: http://lkml.kernel.org/r/1338275765-3217-2-git-send-email-yong.zhang0@gmail.com
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/hexagon/kernel/smp.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/hexagon/kernel/smp.c b/arch/hexagon/kernel/smp.c
index f726462..149fbef 100644
--- a/arch/hexagon/kernel/smp.c
+++ b/arch/hexagon/kernel/smp.c
@@ -180,9 +180,7 @@ void __cpuinit start_secondary(void)
 
 	notify_cpu_starting(cpu);
 
-	ipi_call_lock();
 	set_cpu_online(cpu, true);
-	ipi_call_unlock();
 
 	local_irq_enable();
 

[tip:smp/hotplug] mn10300: SMP: Remove call to ipi_call_lock()/ ipi_call_unlock()

[tip-bot for Yong Zhang]

Commit-ID:  4cbd19fcf9d49f28766415b96eb6201bc263d817
Gitweb:     http://git.kernel.org/tip/4cbd19fcf9d49f28766415b96eb6201bc263d817
Author:     Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Tue, 29 May 2012 15:15:57 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 5 Jun 2012 17:27:12 +0200

mn10300: SMP: Remove call to ipi_call_lock()/ipi_call_unlock()

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 ]

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: peterz@infradead.org
Cc: David Howells <dhowells@redhat.com>
Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
Cc: linux-am33-list@redhat.com
Link: http://lkml.kernel.org/r/1338275765-3217-3-git-send-email-yong.zhang0@gmail.com
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/mn10300/kernel/smp.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/mn10300/kernel/smp.c b/arch/mn10300/kernel/smp.c
index 090d35d..e62c223 100644
--- a/arch/mn10300/kernel/smp.c
+++ b/arch/mn10300/kernel/smp.c
@@ -876,9 +876,7 @@ static void __init smp_online(void)
 
 	notify_cpu_starting(cpu);
 
-	ipi_call_lock();
 	set_cpu_online(cpu, true);
-	ipi_call_unlock();
 
 	local_irq_enable();
 }

[tip:smp/hotplug] parisc: Smp: remove call to ipi_call_lock()/ ipi_call_unlock()

[tip-bot for Yong Zhang]

Commit-ID:  ac4216d6922f90c459d531e051c832dadde3a8f7
Gitweb:     http://git.kernel.org/tip/ac4216d6922f90c459d531e051c832dadde3a8f7
Author:     Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Tue, 29 May 2012 15:15:58 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 5 Jun 2012 17:27:12 +0200

parisc: Smp: remove call to ipi_call_lock()/ipi_call_unlock()

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 ]

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: peterz@infradead.org
Cc: James E.J. Bottomley <jejb@parisc-linux.org>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-parisc@vger.kernel.org
Link: http://lkml.kernel.org/r/1338275765-3217-4-git-send-email-yong.zhang0@gmail.com
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/parisc/kernel/smp.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
index a47828d..6266730 100644
--- a/arch/parisc/kernel/smp.c
+++ b/arch/parisc/kernel/smp.c
@@ -300,9 +300,7 @@ smp_cpu_init(int cpunum)
 
 	notify_cpu_starting(cpunum);
 
-	ipi_call_lock();
 	set_cpu_online(cpunum, true);
-	ipi_call_unlock();
 
 	/* Initialise the idle task for this CPU */
 	atomic_inc(&init_mm.mm_count);

[tip:smp/hotplug] S390: Smp: remove call to ipi_call_lock()/ ipi_call_unlock()

[tip-bot for Yong Zhang]

Commit-ID:  46ce7fbfdbe0be6aaf0e816331aac08a74a00e5a
Gitweb:     http://git.kernel.org/tip/46ce7fbfdbe0be6aaf0e816331aac08a74a00e5a
Author:     Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Tue, 29 May 2012 15:15:59 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 5 Jun 2012 17:27:12 +0200

S390: Smp: remove call to ipi_call_lock()/ipi_call_unlock()

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 ]

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: peterz@infradead.org
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux390@de.ibm.com
Cc: linux-s390@vger.kernel.org
Link: http://lkml.kernel.org/r/1338275765-3217-5-git-send-email-yong.zhang0@gmail.com
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/s390/kernel/smp.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 15cca26..8dca9c2 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -717,9 +717,7 @@ static void __cpuinit smp_start_secondary(void *cpuvoid)
 	init_cpu_vtimer();
 	pfault_init();
 	notify_cpu_starting(smp_processor_id());
-	ipi_call_lock();
 	set_cpu_online(smp_processor_id(), true);
-	ipi_call_unlock();
 	local_irq_enable();
 	/* cpu_idle will call schedule for us */
 	cpu_idle();

[tip:smp/hotplug] tile: SMP: Remove call to ipi_call_lock()/ ipi_call_unlock()

[tip-bot for Yong Zhang]

Commit-ID:  8efdfc3a4ed009c978dab6609d15fb958e7cff12
Gitweb:     http://git.kernel.org/tip/8efdfc3a4ed009c978dab6609d15fb958e7cff12
Author:     Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Tue, 29 May 2012 15:16:00 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 5 Jun 2012 17:27:12 +0200

tile: SMP: Remove call to ipi_call_lock()/ipi_call_unlock()

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 ]

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: peterz@infradead.org
Cc: Chris Metcalf <cmetcalf@tilera.com>
Link: http://lkml.kernel.org/r/1338275765-3217-6-git-send-email-yong.zhang0@gmail.com
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/tile/kernel/smpboot.c |   10 ----------
 1 files changed, 0 insertions(+), 10 deletions(-)

diff --git a/arch/tile/kernel/smpboot.c b/arch/tile/kernel/smpboot.c
index 84873fb..e686c5a 100644
--- a/arch/tile/kernel/smpboot.c
+++ b/arch/tile/kernel/smpboot.c
@@ -198,17 +198,7 @@ void __cpuinit online_secondary(void)
 
 	notify_cpu_starting(smp_processor_id());
 
-	/*
-	 * We need to hold call_lock, so there is no inconsistency
-	 * between the time smp_call_function() determines number of
-	 * IPI recipients, and the time when the determination is made
-	 * for which cpus receive the IPI. Holding this
-	 * lock helps us to not include this cpu in a currently in progress
-	 * smp_call_function().
-	 */
-	ipi_call_lock();
 	set_cpu_online(smp_processor_id(), 1);
-	ipi_call_unlock();
 	__get_cpu_var(cpu_state) = CPU_ONLINE;
 
 	/* Set up tile-specific state for this cpu. */

[tip:smp/hotplug] x86-smp-remove-call-to-ipi_call_lock-ipi_call_unlock

[tip-bot for Yong Zhang]

Commit-ID:  3b6f70fd7dd4e19fc674ec99e389bf0da5589525
Gitweb:     http://git.kernel.org/tip/3b6f70fd7dd4e19fc674ec99e389bf0da5589525
Author:     Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Tue, 29 May 2012 15:16:01 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 5 Jun 2012 17:27:12 +0200

x86-smp-remove-call-to-ipi_call_lock-ipi_call_unlock

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 ]

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: peterz@infradead.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1338275765-3217-7-git-send-email-yong.zhang0@gmail.com
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/smpboot.c |    9 ---------
 arch/x86/xen/smp.c        |    2 --
 2 files changed, 0 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index f56f96d..b2fd28f 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -255,22 +255,13 @@ notrace static void __cpuinit start_secondary(void *unused)
 	check_tsc_sync_target();
 
 	/*
-	 * We need to hold call_lock, so there is no inconsistency
-	 * between the time smp_call_function() determines number of
-	 * IPI recipients, and the time when the determination is made
-	 * for which cpus receive the IPI. Holding this
-	 * lock helps us to not include this cpu in a currently in progress
-	 * smp_call_function().
-	 *
 	 * We need to hold vector_lock so there the set of online cpus
 	 * does not change while we are assigning vectors to cpus.  Holding
 	 * this lock ensures we don't half assign or remove an irq from a cpu.
 	 */
-	ipi_call_lock();
 	lock_vector_lock();
 	set_cpu_online(smp_processor_id(), true);
 	unlock_vector_lock();
-	ipi_call_unlock();
 	per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
 	x86_platform.nmi_init();
 
diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index afb250d..f58dca7 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -80,9 +80,7 @@ static void __cpuinit cpu_bringup(void)
 
 	notify_cpu_starting(cpu);
 
-	ipi_call_lock();
 	set_cpu_online(cpu, true);
-	ipi_call_unlock();
 
 	this_cpu_write(cpu_state, CPU_ONLINE);
 

[tip:smp/hotplug] ia64: SMP: Remove call to ipi_call_lock_irq()/ ipi_call_unlock_irq()

[tip-bot for Yong Zhang]

Commit-ID:  459165e25030c0023cb54f73c14261a3d2f4a244
Gitweb:     http://git.kernel.org/tip/459165e25030c0023cb54f73c14261a3d2f4a244
Author:     Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Tue, 29 May 2012 15:16:02 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 5 Jun 2012 17:27:13 +0200

ia64: SMP: Remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()

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 ]

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: peterz@infradead.org
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: linux-ia64@vger.kernel.org
Link: http://lkml.kernel.org/r/1338275765-3217-8-git-send-email-yong.zhang0@gmail.com
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/ia64/kernel/smpboot.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/ia64/kernel/smpboot.c b/arch/ia64/kernel/smpboot.c
index 1113b8a..963d2db 100644
--- a/arch/ia64/kernel/smpboot.c
+++ b/arch/ia64/kernel/smpboot.c
@@ -382,7 +382,6 @@ smp_callin (void)
 	set_numa_node(cpu_to_node_map[cpuid]);
 	set_numa_mem(local_memory_node(cpu_to_node_map[cpuid]));
 
-	ipi_call_lock_irq();
 	spin_lock(&vector_lock);
 	/* Setup the per cpu irq handling data structures */
 	__setup_vector_irq(cpuid);
@@ -390,7 +389,6 @@ smp_callin (void)
 	set_cpu_online(cpuid, true);
 	per_cpu(cpu_state, cpuid) = CPU_ONLINE;
 	spin_unlock(&vector_lock);
-	ipi_call_unlock_irq();
 
 	smp_setup_percpu_timer();
 

[tip:smp/hotplug] SPARC: SMP: Remove call to ipi_call_lock_irq()/ ipi_call_unlock_irq()

[tip-bot for Yong Zhang]

Commit-ID:  bc6833009583bd5b096ef7aa2bb006854a5a2dce
Gitweb:     http://git.kernel.org/tip/bc6833009583bd5b096ef7aa2bb006854a5a2dce
Author:     Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Tue, 29 May 2012 16:27:33 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 5 Jun 2012 17:27:13 +0200

SPARC: SMP: Remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()

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.

Delay irq enable to after set_cpu_online().

[ tglx: Massaged changelog ]

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: peterz@infradead.org
Cc: sparclinux@vger.kernel.org
Link: http://lkml.kernel.org/r/20120529082732.GA4250@zhy
Acked-by: "David S. Miller" <davem@davemloft.net>
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/sparc/kernel/smp_64.c |    7 +------
 1 files changed, 1 insertions(+), 6 deletions(-)

diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c
index f591598..781bcb1 100644
--- a/arch/sparc/kernel/smp_64.c
+++ b/arch/sparc/kernel/smp_64.c
@@ -103,8 +103,6 @@ void __cpuinit smp_callin(void)
 	if (cheetah_pcache_forced_on)
 		cheetah_enable_pcache();
 
-	local_irq_enable();
-
 	callin_flag = 1;
 	__asm__ __volatile__("membar #Sync\n\t"
 			     "flush  %%g6" : : : "memory");
@@ -124,9 +122,8 @@ void __cpuinit smp_callin(void)
 	while (!cpumask_test_cpu(cpuid, &smp_commenced_mask))
 		rmb();
 
-	ipi_call_lock_irq();
 	set_cpu_online(cpuid, true);
-	ipi_call_unlock_irq();
+	local_irq_enable();
 
 	/* idle thread is expected to have preempt disabled */
 	preempt_disable();
@@ -1308,9 +1305,7 @@ int __cpu_disable(void)
 	mdelay(1);
 	local_irq_disable();
 
-	ipi_call_lock();
 	set_cpu_online(cpu, false);
-	ipi_call_unlock();
 
 	cpu_map_rebuild();
 

[tip:smp/hotplug] POWERPC: Smp: remove call to ipi_call_lock()/ ipi_call_unlock()

[tip-bot for Yong Zhang]

Commit-ID:  72ec61a9e8347375e37c05e23511173d8451c3d4
Gitweb:     http://git.kernel.org/tip/72ec61a9e8347375e37c05e23511173d8451c3d4
Author:     Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Tue, 29 May 2012 15:16:04 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 5 Jun 2012 17:27:13 +0200

POWERPC: Smp: remove call to ipi_call_lock()/ipi_call_unlock()

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 ]

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: peterz@infradead.org
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/1338275765-3217-10-git-send-email-yong.zhang0@gmail.com
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 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();
 

[tip:smp/hotplug] smp: Remove ipi_call_lock[_irq]()/ ipi_call_unlock[_irq]()

[tip-bot for Yong Zhang]

Commit-ID:  8feb8e896d77439146d2e2ab3d0ab55bb5baf5fc
Gitweb:     http://git.kernel.org/tip/8feb8e896d77439146d2e2ab3d0ab55bb5baf5fc
Author:     Yong Zhang <yong.zhang0@gmail.com>
AuthorDate: Tue, 29 May 2012 15:16:05 +0800
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 5 Jun 2012 17:27:14 +0200

smp: Remove ipi_call_lock[_irq]()/ipi_call_unlock[_irq]()

There is no user of those APIs anymore, just remove it.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1338275765-3217-11-git-send-email-yong.zhang0@gmail.com
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/smp.h |    4 ----
 kernel/smp.c        |   20 --------------------
 2 files changed, 0 insertions(+), 24 deletions(-)

diff --git a/include/linux/smp.h b/include/linux/smp.h
index 717fb74..a34d4f1 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -90,10 +90,6 @@ void kick_all_cpus_sync(void);
 void __init call_function_init(void);
 void generic_smp_call_function_single_interrupt(void);
 void generic_smp_call_function_interrupt(void);
-void ipi_call_lock(void);
-void ipi_call_unlock(void);
-void ipi_call_lock_irq(void);
-void ipi_call_unlock_irq(void);
 #else
 static inline void call_function_init(void) { }
 #endif
diff --git a/kernel/smp.c b/kernel/smp.c
index d0ae5b2..29dd40a 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -581,26 +581,6 @@ int smp_call_function(smp_call_func_t func, void *info, int wait)
 	return 0;
 }
 EXPORT_SYMBOL(smp_call_function);
-
-void ipi_call_lock(void)
-{
-	raw_spin_lock(&call_function.lock);
-}
-
-void ipi_call_unlock(void)
-{
-	raw_spin_unlock(&call_function.lock);
-}
-
-void ipi_call_lock_irq(void)
-{
-	raw_spin_lock_irq(&call_function.lock);
-}
-
-void ipi_call_unlock_irq(void)
-{
-	raw_spin_unlock_irq(&call_function.lock);
-}
 #endif /* USE_GENERIC_SMP_HELPERS */
 
 /* Setup configured maximum number of CPUs to activate */

Re: [RFC PATCH 00/10] Cleanup ipi_call_lock[_irq]()/ipi_call_unlock[_irq]()

[Paul E. McKenney]

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
> 

Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()

[Paul E. McKenney]

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
> 

Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()

[Peter Zijlstra]

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.

Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()

[Paul E. McKenney]

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

Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()

[Yong Zhang]

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

Re: [RFC PATCH 09/10] POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()

[Paul E. McKenney]

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
>