All of lore.kernel.org
 help / color / mirror / Atom feed
* [PATCH] irqchip/gicv3: silence noisy DEBUG_PER_CPU_MAPS warning
@ 2016-09-19 17:29 ` James Morse
  0 siblings, 0 replies; 6+ messages in thread
From: James Morse @ 2016-09-19 17:29 UTC (permalink / raw)
  To: linux-arm-kernel

gic_raise_softirq() walks the list of cpus using for_each_cpu(), it calls
gic_compute_target_list() which advances the iterator by the number of
CPUs in the cluster.

If gic_compute_target_list() reaches the last CPU it leaves the iterator
pointing at the last CPU. This means the next time round the for_each_cpu()
loop cpumask_next() will be called with an invalid CPU.

This triggers a warning when built with CONFIG_DEBUG_PER_CPU_MAPS:
[    3.077738] GICv3: CPU1: found redistributor 1 region 0:0x000000002f120000
[    3.077943] CPU1: Booted secondary processor [410fd0f0]
[    3.078542] ------------[ cut here ]------------
[    3.078746] WARNING: CPU: 1 PID: 0 at ../include/linux/cpumask.h:121 gic_raise_softirq+0x12c/0x170
[    3.078812] Modules linked in:
[    3.078869]
[    3.078930] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.8.0-rc5+ #5188
[    3.078994] Hardware name: Foundation-v8A (DT)
[    3.079059] task: ffff80087a1a0080 task.stack: ffff80087a19c000
[    3.079145] PC is at gic_raise_softirq+0x12c/0x170
[    3.079226] LR is at gic_raise_softirq+0xa4/0x170
[    3.079296] pc : [<ffff0000083ead24>] lr : [<ffff0000083eac9c>] pstate: 200001c9
[    3.081139] Call trace:
[    3.081202] Exception stack(0xffff80087a19fbe0 to 0xffff80087a19fd10)

[    3.082269] [<ffff0000083ead24>] gic_raise_softirq+0x12c/0x170
[    3.082354] [<ffff00000808e614>] smp_send_reschedule+0x34/0x40
[    3.082433] [<ffff0000080e80a0>] resched_curr+0x50/0x88
[    3.082512] [<ffff0000080e89d0>] check_preempt_curr+0x60/0xd0
[    3.082593] [<ffff0000080e8a60>] ttwu_do_wakeup+0x20/0xe8
[    3.082672] [<ffff0000080e8bb8>] ttwu_do_activate+0x90/0xc0
[    3.082753] [<ffff0000080ea9a4>] try_to_wake_up+0x224/0x370
[    3.082836] [<ffff0000080eabc8>] default_wake_function+0x10/0x18
[    3.082920] [<ffff000008103134>] __wake_up_common+0x5c/0xa0
[    3.083003] [<ffff0000081031f4>] __wake_up_locked+0x14/0x20
[    3.083086] [<ffff000008103f80>] complete+0x40/0x60
[    3.083168] [<ffff00000808df7c>] secondary_start_kernel+0x15c/0x1d0
[    3.083240] [<00000000808911a4>] 0x808911a4
[    3.113401] Detected PIPT I-cache on CPU2

Avoid updating the iterator if the next call to cpumask_next() would
cause the for_each_cpu() loop to exit.

There is no change to gic_raise_softirq()'s behaviour, (cpumask_next()s
eventual call to _find_next_bit() will return early as start >= nbits),
this patch just silences the warning.

Signed-off-by: James Morse <james.morse@arm.com>
---
 drivers/irqchip/irq-gic-v3.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index ede5672ab34d..9e37c447cc2c 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -548,6 +548,7 @@ static int gic_starting_cpu(unsigned int cpu)
 static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
 				   unsigned long cluster_id)
 {
+	int next_cpu;
 	int cpu = *base_cpu;
 	unsigned long mpidr = cpu_logical_map(cpu);
 	u16 tlist = 0;
@@ -562,9 +563,10 @@ static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
 
 		tlist |= 1 << (mpidr & 0xf);
 
-		cpu = cpumask_next(cpu, mask);
-		if (cpu >= nr_cpu_ids)
+		next_cpu = cpumask_next(cpu, mask);
+		if (next_cpu >= nr_cpu_ids)
 			goto out;
+		cpu = next_cpu;
 
 		mpidr = cpu_logical_map(cpu);
 
-- 
2.8.0.rc3

^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH] irqchip/gicv3: silence noisy DEBUG_PER_CPU_MAPS warning
@ 2016-09-19 17:29 ` James Morse
  0 siblings, 0 replies; 6+ messages in thread
From: James Morse @ 2016-09-19 17:29 UTC (permalink / raw)
  To: linux-kernel
  Cc: linux-arm-kernel, Thomas Gleixner, Jason Cooper, Marc Zyngier,
	James Morse

gic_raise_softirq() walks the list of cpus using for_each_cpu(), it calls
gic_compute_target_list() which advances the iterator by the number of
CPUs in the cluster.

If gic_compute_target_list() reaches the last CPU it leaves the iterator
pointing at the last CPU. This means the next time round the for_each_cpu()
loop cpumask_next() will be called with an invalid CPU.

This triggers a warning when built with CONFIG_DEBUG_PER_CPU_MAPS:
[    3.077738] GICv3: CPU1: found redistributor 1 region 0:0x000000002f120000
[    3.077943] CPU1: Booted secondary processor [410fd0f0]
[    3.078542] ------------[ cut here ]------------
[    3.078746] WARNING: CPU: 1 PID: 0 at ../include/linux/cpumask.h:121 gic_raise_softirq+0x12c/0x170
[    3.078812] Modules linked in:
[    3.078869]
[    3.078930] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.8.0-rc5+ #5188
[    3.078994] Hardware name: Foundation-v8A (DT)
[    3.079059] task: ffff80087a1a0080 task.stack: ffff80087a19c000
[    3.079145] PC is at gic_raise_softirq+0x12c/0x170
[    3.079226] LR is at gic_raise_softirq+0xa4/0x170
[    3.079296] pc : [<ffff0000083ead24>] lr : [<ffff0000083eac9c>] pstate: 200001c9
[    3.081139] Call trace:
[    3.081202] Exception stack(0xffff80087a19fbe0 to 0xffff80087a19fd10)

[    3.082269] [<ffff0000083ead24>] gic_raise_softirq+0x12c/0x170
[    3.082354] [<ffff00000808e614>] smp_send_reschedule+0x34/0x40
[    3.082433] [<ffff0000080e80a0>] resched_curr+0x50/0x88
[    3.082512] [<ffff0000080e89d0>] check_preempt_curr+0x60/0xd0
[    3.082593] [<ffff0000080e8a60>] ttwu_do_wakeup+0x20/0xe8
[    3.082672] [<ffff0000080e8bb8>] ttwu_do_activate+0x90/0xc0
[    3.082753] [<ffff0000080ea9a4>] try_to_wake_up+0x224/0x370
[    3.082836] [<ffff0000080eabc8>] default_wake_function+0x10/0x18
[    3.082920] [<ffff000008103134>] __wake_up_common+0x5c/0xa0
[    3.083003] [<ffff0000081031f4>] __wake_up_locked+0x14/0x20
[    3.083086] [<ffff000008103f80>] complete+0x40/0x60
[    3.083168] [<ffff00000808df7c>] secondary_start_kernel+0x15c/0x1d0
[    3.083240] [<00000000808911a4>] 0x808911a4
[    3.113401] Detected PIPT I-cache on CPU2

Avoid updating the iterator if the next call to cpumask_next() would
cause the for_each_cpu() loop to exit.

There is no change to gic_raise_softirq()'s behaviour, (cpumask_next()s
eventual call to _find_next_bit() will return early as start >= nbits),
this patch just silences the warning.

Signed-off-by: James Morse <james.morse@arm.com>
---
 drivers/irqchip/irq-gic-v3.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index ede5672ab34d..9e37c447cc2c 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -548,6 +548,7 @@ static int gic_starting_cpu(unsigned int cpu)
 static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
 				   unsigned long cluster_id)
 {
+	int next_cpu;
 	int cpu = *base_cpu;
 	unsigned long mpidr = cpu_logical_map(cpu);
 	u16 tlist = 0;
@@ -562,9 +563,10 @@ static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
 
 		tlist |= 1 << (mpidr & 0xf);
 
-		cpu = cpumask_next(cpu, mask);
-		if (cpu >= nr_cpu_ids)
+		next_cpu = cpumask_next(cpu, mask);
+		if (next_cpu >= nr_cpu_ids)
 			goto out;
+		cpu = next_cpu;
 
 		mpidr = cpu_logical_map(cpu);
 
-- 
2.8.0.rc3

^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [PATCH] irqchip/gicv3: silence noisy DEBUG_PER_CPU_MAPS warning
  2016-09-19 17:29 ` James Morse
@ 2016-09-19 17:38   ` Marc Zyngier
  -1 siblings, 0 replies; 6+ messages in thread
From: Marc Zyngier @ 2016-09-19 17:38 UTC (permalink / raw)
  To: linux-arm-kernel

Hi James,

On 19/09/16 18:29, James Morse wrote:
> gic_raise_softirq() walks the list of cpus using for_each_cpu(), it calls
> gic_compute_target_list() which advances the iterator by the number of
> CPUs in the cluster.
> 
> If gic_compute_target_list() reaches the last CPU it leaves the iterator
> pointing at the last CPU. This means the next time round the for_each_cpu()
> loop cpumask_next() will be called with an invalid CPU.
> 
> This triggers a warning when built with CONFIG_DEBUG_PER_CPU_MAPS:
> [    3.077738] GICv3: CPU1: found redistributor 1 region 0:0x000000002f120000
> [    3.077943] CPU1: Booted secondary processor [410fd0f0]
> [    3.078542] ------------[ cut here ]------------
> [    3.078746] WARNING: CPU: 1 PID: 0 at ../include/linux/cpumask.h:121 gic_raise_softirq+0x12c/0x170
> [    3.078812] Modules linked in:
> [    3.078869]
> [    3.078930] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.8.0-rc5+ #5188
> [    3.078994] Hardware name: Foundation-v8A (DT)
> [    3.079059] task: ffff80087a1a0080 task.stack: ffff80087a19c000
> [    3.079145] PC is at gic_raise_softirq+0x12c/0x170
> [    3.079226] LR is at gic_raise_softirq+0xa4/0x170
> [    3.079296] pc : [<ffff0000083ead24>] lr : [<ffff0000083eac9c>] pstate: 200001c9
> [    3.081139] Call trace:
> [    3.081202] Exception stack(0xffff80087a19fbe0 to 0xffff80087a19fd10)
> 
> [    3.082269] [<ffff0000083ead24>] gic_raise_softirq+0x12c/0x170
> [    3.082354] [<ffff00000808e614>] smp_send_reschedule+0x34/0x40
> [    3.082433] [<ffff0000080e80a0>] resched_curr+0x50/0x88
> [    3.082512] [<ffff0000080e89d0>] check_preempt_curr+0x60/0xd0
> [    3.082593] [<ffff0000080e8a60>] ttwu_do_wakeup+0x20/0xe8
> [    3.082672] [<ffff0000080e8bb8>] ttwu_do_activate+0x90/0xc0
> [    3.082753] [<ffff0000080ea9a4>] try_to_wake_up+0x224/0x370
> [    3.082836] [<ffff0000080eabc8>] default_wake_function+0x10/0x18
> [    3.082920] [<ffff000008103134>] __wake_up_common+0x5c/0xa0
> [    3.083003] [<ffff0000081031f4>] __wake_up_locked+0x14/0x20
> [    3.083086] [<ffff000008103f80>] complete+0x40/0x60
> [    3.083168] [<ffff00000808df7c>] secondary_start_kernel+0x15c/0x1d0
> [    3.083240] [<00000000808911a4>] 0x808911a4
> [    3.113401] Detected PIPT I-cache on CPU2
> 
> Avoid updating the iterator if the next call to cpumask_next() would
> cause the for_each_cpu() loop to exit.
> 
> There is no change to gic_raise_softirq()'s behaviour, (cpumask_next()s
> eventual call to _find_next_bit() will return early as start >= nbits),
> this patch just silences the warning.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
>  drivers/irqchip/irq-gic-v3.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index ede5672ab34d..9e37c447cc2c 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -548,6 +548,7 @@ static int gic_starting_cpu(unsigned int cpu)
>  static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
>  				   unsigned long cluster_id)
>  {
> +	int next_cpu;
>  	int cpu = *base_cpu;
>  	unsigned long mpidr = cpu_logical_map(cpu);
>  	u16 tlist = 0;
> @@ -562,9 +563,10 @@ static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
>  
>  		tlist |= 1 << (mpidr & 0xf);
>  
> -		cpu = cpumask_next(cpu, mask);
> -		if (cpu >= nr_cpu_ids)
> +		next_cpu = cpumask_next(cpu, mask);
> +		if (next_cpu >= nr_cpu_ids)
>  			goto out;
> +		cpu = next_cpu;
>  
>  		mpidr = cpu_logical_map(cpu);
>  
> 

It took me a while to convince myself that the original code was
correct, and it obviously wasn't... Oh well, paper bag time.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>

Thomas, any chance you could pick that one for -rc8?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

^ permalink raw reply	[flat|nested] 6+ messages in thread
* Re: [PATCH] irqchip/gicv3: silence noisy DEBUG_PER_CPU_MAPS warning
@ 2016-09-19 17:38   ` Marc Zyngier
  0 siblings, 0 replies; 6+ messages in thread
From: Marc Zyngier @ 2016-09-19 17:38 UTC (permalink / raw)
  To: James Morse, linux-kernel; +Cc: linux-arm-kernel, Thomas Gleixner, Jason Cooper

Hi James,

On 19/09/16 18:29, James Morse wrote:
> gic_raise_softirq() walks the list of cpus using for_each_cpu(), it calls
> gic_compute_target_list() which advances the iterator by the number of
> CPUs in the cluster.
> 
> If gic_compute_target_list() reaches the last CPU it leaves the iterator
> pointing at the last CPU. This means the next time round the for_each_cpu()
> loop cpumask_next() will be called with an invalid CPU.
> 
> This triggers a warning when built with CONFIG_DEBUG_PER_CPU_MAPS:
> [    3.077738] GICv3: CPU1: found redistributor 1 region 0:0x000000002f120000
> [    3.077943] CPU1: Booted secondary processor [410fd0f0]
> [    3.078542] ------------[ cut here ]------------
> [    3.078746] WARNING: CPU: 1 PID: 0 at ../include/linux/cpumask.h:121 gic_raise_softirq+0x12c/0x170
> [    3.078812] Modules linked in:
> [    3.078869]
> [    3.078930] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.8.0-rc5+ #5188
> [    3.078994] Hardware name: Foundation-v8A (DT)
> [    3.079059] task: ffff80087a1a0080 task.stack: ffff80087a19c000
> [    3.079145] PC is at gic_raise_softirq+0x12c/0x170
> [    3.079226] LR is at gic_raise_softirq+0xa4/0x170
> [    3.079296] pc : [<ffff0000083ead24>] lr : [<ffff0000083eac9c>] pstate: 200001c9
> [    3.081139] Call trace:
> [    3.081202] Exception stack(0xffff80087a19fbe0 to 0xffff80087a19fd10)
> 
> [    3.082269] [<ffff0000083ead24>] gic_raise_softirq+0x12c/0x170
> [    3.082354] [<ffff00000808e614>] smp_send_reschedule+0x34/0x40
> [    3.082433] [<ffff0000080e80a0>] resched_curr+0x50/0x88
> [    3.082512] [<ffff0000080e89d0>] check_preempt_curr+0x60/0xd0
> [    3.082593] [<ffff0000080e8a60>] ttwu_do_wakeup+0x20/0xe8
> [    3.082672] [<ffff0000080e8bb8>] ttwu_do_activate+0x90/0xc0
> [    3.082753] [<ffff0000080ea9a4>] try_to_wake_up+0x224/0x370
> [    3.082836] [<ffff0000080eabc8>] default_wake_function+0x10/0x18
> [    3.082920] [<ffff000008103134>] __wake_up_common+0x5c/0xa0
> [    3.083003] [<ffff0000081031f4>] __wake_up_locked+0x14/0x20
> [    3.083086] [<ffff000008103f80>] complete+0x40/0x60
> [    3.083168] [<ffff00000808df7c>] secondary_start_kernel+0x15c/0x1d0
> [    3.083240] [<00000000808911a4>] 0x808911a4
> [    3.113401] Detected PIPT I-cache on CPU2
> 
> Avoid updating the iterator if the next call to cpumask_next() would
> cause the for_each_cpu() loop to exit.
> 
> There is no change to gic_raise_softirq()'s behaviour, (cpumask_next()s
> eventual call to _find_next_bit() will return early as start >= nbits),
> this patch just silences the warning.
> 
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
>  drivers/irqchip/irq-gic-v3.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index ede5672ab34d..9e37c447cc2c 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -548,6 +548,7 @@ static int gic_starting_cpu(unsigned int cpu)
>  static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
>  				   unsigned long cluster_id)
>  {
> +	int next_cpu;
>  	int cpu = *base_cpu;
>  	unsigned long mpidr = cpu_logical_map(cpu);
>  	u16 tlist = 0;
> @@ -562,9 +563,10 @@ static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
>  
>  		tlist |= 1 << (mpidr & 0xf);
>  
> -		cpu = cpumask_next(cpu, mask);
> -		if (cpu >= nr_cpu_ids)
> +		next_cpu = cpumask_next(cpu, mask);
> +		if (next_cpu >= nr_cpu_ids)
>  			goto out;
> +		cpu = next_cpu;
>  
>  		mpidr = cpu_logical_map(cpu);
>  
> 

It took me a while to convince myself that the original code was
correct, and it obviously wasn't... Oh well, paper bag time.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>

Thomas, any chance you could pick that one for -rc8?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

^ permalink raw reply	[flat|nested] 6+ messages in thread
* [tip:irq/urgent] irqchip/gicv3: Silence noisy DEBUG_PER_CPU_MAPS warning
  2016-09-19 17:29 ` James Morse
  (?)
  (?)
@ 2016-09-19 19:13 ` tip-bot for James Morse
  -1 siblings, 0 replies; 6+ messages in thread
From: tip-bot for James Morse @ 2016-09-19 19:13 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: jason, tglx, marc.zyngier, mingo, james.morse, linux-kernel, hpa

Commit-ID:  7e947926fc3bfa095644c2933ec209128cbfd61e
Gitweb:     http://git.kernel.org/tip/7e947926fc3bfa095644c2933ec209128cbfd61e
Author:     James Morse <james.morse@arm.com>
AuthorDate: Mon, 19 Sep 2016 18:29:15 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 19 Sep 2016 21:07:12 +0200

irqchip/gicv3: Silence noisy DEBUG_PER_CPU_MAPS warning

gic_raise_softirq() walks the list of cpus using for_each_cpu(), it calls
gic_compute_target_list() which advances the iterator by the number of
CPUs in the cluster.

If gic_compute_target_list() reaches the last CPU it leaves the iterator
pointing at the last CPU. This means the next time round the for_each_cpu()
loop cpumask_next() will be called with an invalid CPU.

This triggers a warning when built with CONFIG_DEBUG_PER_CPU_MAPS:
[    3.077738] GICv3: CPU1: found redistributor 1 region 0:0x000000002f120000
[    3.077943] CPU1: Booted secondary processor [410fd0f0]
[    3.078542] ------------[ cut here ]------------
[    3.078746] WARNING: CPU: 1 PID: 0 at ../include/linux/cpumask.h:121 gic_raise_softirq+0x12c/0x170
[    3.078812] Modules linked in:
[    3.078869]
[    3.078930] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.8.0-rc5+ #5188
[    3.078994] Hardware name: Foundation-v8A (DT)
[    3.079059] task: ffff80087a1a0080 task.stack: ffff80087a19c000
[    3.079145] PC is at gic_raise_softirq+0x12c/0x170
[    3.079226] LR is at gic_raise_softirq+0xa4/0x170
[    3.079296] pc : [<ffff0000083ead24>] lr : [<ffff0000083eac9c>] pstate: 200001c9
[    3.081139] Call trace:
[    3.081202] Exception stack(0xffff80087a19fbe0 to 0xffff80087a19fd10)

[    3.082269] [<ffff0000083ead24>] gic_raise_softirq+0x12c/0x170
[    3.082354] [<ffff00000808e614>] smp_send_reschedule+0x34/0x40
[    3.082433] [<ffff0000080e80a0>] resched_curr+0x50/0x88
[    3.082512] [<ffff0000080e89d0>] check_preempt_curr+0x60/0xd0
[    3.082593] [<ffff0000080e8a60>] ttwu_do_wakeup+0x20/0xe8
[    3.082672] [<ffff0000080e8bb8>] ttwu_do_activate+0x90/0xc0
[    3.082753] [<ffff0000080ea9a4>] try_to_wake_up+0x224/0x370
[    3.082836] [<ffff0000080eabc8>] default_wake_function+0x10/0x18
[    3.082920] [<ffff000008103134>] __wake_up_common+0x5c/0xa0
[    3.083003] [<ffff0000081031f4>] __wake_up_locked+0x14/0x20
[    3.083086] [<ffff000008103f80>] complete+0x40/0x60
[    3.083168] [<ffff00000808df7c>] secondary_start_kernel+0x15c/0x1d0
[    3.083240] [<00000000808911a4>] 0x808911a4
[    3.113401] Detected PIPT I-cache on CPU2

Avoid updating the iterator if the next call to cpumask_next() would
cause the for_each_cpu() loop to exit.

There is no change to gic_raise_softirq()'s behaviour, (cpumask_next()s
eventual call to _find_next_bit() will return early as start >= nbits),
this patch just silences the warning.

Fixes: 021f653791ad ("irqchip: gic-v3: Initial support for GICv3")
Signed-off-by: James Morse <james.morse@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Jason Cooper <jason@lakedaemon.net>
Link: http://lkml.kernel.org/r/1474306155-3303-1-git-send-email-james.morse@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 drivers/irqchip/irq-gic-v3.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index ede5672..f39ab57 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -548,8 +548,8 @@ static int gic_starting_cpu(unsigned int cpu)
 static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
 				   unsigned long cluster_id)
 {
-	int cpu = *base_cpu;
 	unsigned long mpidr = cpu_logical_map(cpu);
+	int next_cpu, cpu = *base_cpu;
 	u16 tlist = 0;
 
 	while (cpu < nr_cpu_ids) {
@@ -562,9 +562,10 @@ static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
 
 		tlist |= 1 << (mpidr & 0xf);
 
-		cpu = cpumask_next(cpu, mask);
-		if (cpu >= nr_cpu_ids)
+		next_cpu = cpumask_next(cpu, mask);
+		if (next_cpu >= nr_cpu_ids)
 			goto out;
+		cpu = next_cpu;
 
 		mpidr = cpu_logical_map(cpu);
 

^ permalink raw reply related	[flat|nested] 6+ messages in thread
* [tip:irq/urgent] irqchip/gicv3: Silence noisy DEBUG_PER_CPU_MAPS warning
  2016-09-19 17:29 ` James Morse
                   ` (2 preceding siblings ...)
  (?)
@ 2016-09-19 23:48 ` tip-bot for James Morse
  -1 siblings, 0 replies; 6+ messages in thread
From: tip-bot for James Morse @ 2016-09-19 23:48 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: tglx, james.morse, hpa, jason, linux-kernel, marc.zyngier, mingo

Commit-ID:  727653d6ce7103b245eb8041f55dd5885f4c3289
Gitweb:     http://git.kernel.org/tip/727653d6ce7103b245eb8041f55dd5885f4c3289
Author:     James Morse <james.morse@arm.com>
AuthorDate: Mon, 19 Sep 2016 18:29:15 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 20 Sep 2016 01:43:23 +0200

irqchip/gicv3: Silence noisy DEBUG_PER_CPU_MAPS warning

gic_raise_softirq() walks the list of cpus using for_each_cpu(), it calls
gic_compute_target_list() which advances the iterator by the number of
CPUs in the cluster.

If gic_compute_target_list() reaches the last CPU it leaves the iterator
pointing at the last CPU. This means the next time round the for_each_cpu()
loop cpumask_next() will be called with an invalid CPU.

This triggers a warning when built with CONFIG_DEBUG_PER_CPU_MAPS:
[    3.077738] GICv3: CPU1: found redistributor 1 region 0:0x000000002f120000
[    3.077943] CPU1: Booted secondary processor [410fd0f0]
[    3.078542] ------------[ cut here ]------------
[    3.078746] WARNING: CPU: 1 PID: 0 at ../include/linux/cpumask.h:121 gic_raise_softirq+0x12c/0x170
[    3.078812] Modules linked in:
[    3.078869]
[    3.078930] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.8.0-rc5+ #5188
[    3.078994] Hardware name: Foundation-v8A (DT)
[    3.079059] task: ffff80087a1a0080 task.stack: ffff80087a19c000
[    3.079145] PC is at gic_raise_softirq+0x12c/0x170
[    3.079226] LR is at gic_raise_softirq+0xa4/0x170
[    3.079296] pc : [<ffff0000083ead24>] lr : [<ffff0000083eac9c>] pstate: 200001c9
[    3.081139] Call trace:
[    3.081202] Exception stack(0xffff80087a19fbe0 to 0xffff80087a19fd10)

[    3.082269] [<ffff0000083ead24>] gic_raise_softirq+0x12c/0x170
[    3.082354] [<ffff00000808e614>] smp_send_reschedule+0x34/0x40
[    3.082433] [<ffff0000080e80a0>] resched_curr+0x50/0x88
[    3.082512] [<ffff0000080e89d0>] check_preempt_curr+0x60/0xd0
[    3.082593] [<ffff0000080e8a60>] ttwu_do_wakeup+0x20/0xe8
[    3.082672] [<ffff0000080e8bb8>] ttwu_do_activate+0x90/0xc0
[    3.082753] [<ffff0000080ea9a4>] try_to_wake_up+0x224/0x370
[    3.082836] [<ffff0000080eabc8>] default_wake_function+0x10/0x18
[    3.082920] [<ffff000008103134>] __wake_up_common+0x5c/0xa0
[    3.083003] [<ffff0000081031f4>] __wake_up_locked+0x14/0x20
[    3.083086] [<ffff000008103f80>] complete+0x40/0x60
[    3.083168] [<ffff00000808df7c>] secondary_start_kernel+0x15c/0x1d0
[    3.083240] [<00000000808911a4>] 0x808911a4
[    3.113401] Detected PIPT I-cache on CPU2

Avoid updating the iterator if the next call to cpumask_next() would
cause the for_each_cpu() loop to exit.

There is no change to gic_raise_softirq()'s behaviour, (cpumask_next()s
eventual call to _find_next_bit() will return early as start >= nbits),
this patch just silences the warning.

Fixes: 021f653791ad ("irqchip: gic-v3: Initial support for GICv3")
Signed-off-by: James Morse <james.morse@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Jason Cooper <jason@lakedaemon.net>
Link: http://lkml.kernel.org/r/1474306155-3303-1-git-send-email-james.morse@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 drivers/irqchip/irq-gic-v3.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index ede5672..da6c0ba 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -548,7 +548,7 @@ static int gic_starting_cpu(unsigned int cpu)
 static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
 				   unsigned long cluster_id)
 {
-	int cpu = *base_cpu;
+	int next_cpu, cpu = *base_cpu;
 	unsigned long mpidr = cpu_logical_map(cpu);
 	u16 tlist = 0;
 
@@ -562,9 +562,10 @@ static u16 gic_compute_target_list(int *base_cpu, const struct cpumask *mask,
 
 		tlist |= 1 << (mpidr & 0xf);
 
-		cpu = cpumask_next(cpu, mask);
-		if (cpu >= nr_cpu_ids)
+		next_cpu = cpumask_next(cpu, mask);
+		if (next_cpu >= nr_cpu_ids)
 			goto out;
+		cpu = next_cpu;
 
 		mpidr = cpu_logical_map(cpu);
 

^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2016-09-19 23:48 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2016-09-19 17:29 [PATCH] irqchip/gicv3: silence noisy DEBUG_PER_CPU_MAPS warning James Morse
2016-09-19 17:29 ` James Morse
2016-09-19 17:38 ` Marc Zyngier
2016-09-19 17:38   ` Marc Zyngier
2016-09-19 19:13 ` [tip:irq/urgent] irqchip/gicv3: Silence " tip-bot for James Morse
2016-09-19 23:48 ` tip-bot for James Morse

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.