Re: [PATCH] rcu: Use per_cpu_ptr to get the pointer of per_cpu variable

Re: [PATCH] rcu: Use per_cpu_ptr to get the pointer of per_cpu variable

[Uladzislau Rezki]

On Wed, Jun 30, 2021 at 10:08:02PM +0800, Liu Song wrote:
> From: Liu Song <liu.song11@zte.com.cn>
> 
> In rcu, most codes have used per_cpu_ptr to obtain per_cpu variable
> pointers. This patch adjusts a few codes that have not done so.
> 
> Signed-off-by: Liu Song <liu.song11@zte.com.cn>
> ---
>  kernel/rcu/tasks.h      | 2 +-
>  kernel/rcu/tree.c       | 4 ++--
>  kernel/rcu/tree_stall.h | 2 +-
>  3 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> index 350ebf5051f9..0275217cb6e4 100644
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -875,7 +875,7 @@ static void trc_read_check_handler(void *t_in)
>  	// Allow future IPIs to be sent on CPU and for task.
>  	// Also order this IPI handler against any later manipulations of
>  	// the intended task.
> -	smp_store_release(&per_cpu(trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
> +	smp_store_release(per_cpu_ptr(&trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
>  	smp_store_release(&texp->trc_ipi_to_cpu, -1); // ^^^
>  }
>  
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 8e78b2430c16..5cab8e39a731 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -399,7 +399,7 @@ bool rcu_eqs_special_set(int cpu)
>  	int old;
>  	int new;
>  	int new_old;
> -	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
> +	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
>  
>  	new_old = atomic_read(&rdp->dynticks);
>  	do {
> @@ -1333,7 +1333,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
>  	 */
>  	jtsq = READ_ONCE(jiffies_to_sched_qs);
>  	ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu);
> -	rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu);
> +	rnhqp = per_cpu_ptr(&rcu_data.rcu_need_heavy_qs, rdp->cpu);
>  	if (!READ_ONCE(*rnhqp) &&
>  	    (time_after(jiffies, rcu_state.gp_start + jtsq * 2) ||
>  	     time_after(jiffies, rcu_state.jiffies_resched) ||
> diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
> index 59b95cc5cbdf..990fdb793d57 100644
> --- a/kernel/rcu/tree_stall.h
> +++ b/kernel/rcu/tree_stall.h
> @@ -349,7 +349,7 @@ static void rcu_dump_cpu_stacks(void)
>  
>  static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
>  {
> -	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
> +	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
>  
>  	sprintf(cp, "last_accelerate: %04lx/%04lx dyntick_enabled: %d",
>  		rdp->last_accelerate & 0xffff, jiffies & 0xffff,
> -- 
> 2.20.1
> 
To me it looks OK.

Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

--
Vlad Rezki

Re: [PATCH] rcu: Use per_cpu_ptr to get the pointer of per_cpu variable

[Neeraj Upadhyay]

On 6/30/2021 7:38 PM, Liu Song wrote:
> From: Liu Song <liu.song11@zte.com.cn>
> 
> In rcu, most codes have used per_cpu_ptr to obtain per_cpu variable
> pointers. This patch adjusts a few codes that have not done so.
> 

Minor: Can we also add below statement?
"This patch doesn't introduce any functional change."

> Signed-off-by: Liu Song <liu.song11@zte.com.cn>
> ---
>   kernel/rcu/tasks.h      | 2 +-
>   kernel/rcu/tree.c       | 4 ++--
>   kernel/rcu/tree_stall.h | 2 +-
>   3 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> index 350ebf5051f9..0275217cb6e4 100644
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -875,7 +875,7 @@ static void trc_read_check_handler(void *t_in)
>   	// Allow future IPIs to be sent on CPU and for task.
>   	// Also order this IPI handler against any later manipulations of
>   	// the intended task.
> -	smp_store_release(&per_cpu(trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
> +	smp_store_release(per_cpu_ptr(&trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
>   	smp_store_release(&texp->trc_ipi_to_cpu, -1); // ^^^
>   }
>   
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 8e78b2430c16..5cab8e39a731 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -399,7 +399,7 @@ bool rcu_eqs_special_set(int cpu)
>   	int old;
>   	int new;
>   	int new_old;
> -	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
> +	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);

rcu_eqs_special_set() does not exist in rcu dev branch [1]; so this 
might need rebase.


[1]
https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/tree/kernel/rcu/tree.c?h=dev

>   
>   	new_old = atomic_read(&rdp->dynticks);
>   	do {
> @@ -1333,7 +1333,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
>   	 */
>   	jtsq = READ_ONCE(jiffies_to_sched_qs);
>   	ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu);
> -	rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu);
> +	rnhqp = per_cpu_ptr(&rcu_data.rcu_need_heavy_qs, rdp->cpu);
>   	if (!READ_ONCE(*rnhqp) &&
>   	    (time_after(jiffies, rcu_state.gp_start + jtsq * 2) ||
>   	     time_after(jiffies, rcu_state.jiffies_resched) ||
> diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
> index 59b95cc5cbdf..990fdb793d57 100644
> --- a/kernel/rcu/tree_stall.h
> +++ b/kernel/rcu/tree_stall.h
> @@ -349,7 +349,7 @@ static void rcu_dump_cpu_stacks(void)
>   
>   static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
>   {
> -	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
> +	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
>   
>   	sprintf(cp, "last_accelerate: %04lx/%04lx dyntick_enabled: %d",
>   		rdp->last_accelerate & 0xffff, jiffies & 0xffff,
>

Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>



Thanks
Neeraj

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a 
member of the Code Aurora Forum, hosted by The Linux Foundation

Re: [PATCH] rcu: Use per_cpu_ptr to get the pointer of per_cpu variable

[Paul E. McKenney]

On Thu, Jul 01, 2021 at 08:24:32PM +0530, Neeraj Upadhyay wrote:
> 
> 
> On 6/30/2021 7:38 PM, Liu Song wrote:
> > From: Liu Song <liu.song11@zte.com.cn>
> > 
> > In rcu, most codes have used per_cpu_ptr to obtain per_cpu variable
> > pointers. This patch adjusts a few codes that have not done so.
> > 
> 
> Minor: Can we also add below statement?
> "This patch doesn't introduce any functional change."
> 
> > Signed-off-by: Liu Song <liu.song11@zte.com.cn>

Applied with the usual wordsmithing, including adding words to this
effect, so thank you all!  I removed the obsolete chunk that Neeraj
pointed out as well.

Please take a look and check to see if all is well.

							Thanx, Paul

------------------------------------------------------------------------

commit 9a6b5a10785f4d9b4f073736e6648fa3851882bd
Author: Liu Song <liu.song11@zte.com.cn>
Date:   Wed Jun 30 22:08:02 2021 +0800

    rcu: Use per_cpu_ptr to get the pointer of per_cpu variable
    
    There are a few remaining locations in kernel/rcu that still use
    "&per_cpu()".  This commit replaces them with "per_cpu_ptr(&)", and does
    not introduce any functional change..
    
    Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
    Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
    Signed-off-by: Liu Song <liu.song11@zte.com.cn>
    Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index f9f52daacd1c..806160c44b17 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -923,7 +923,7 @@ static void trc_read_check_handler(void *t_in)
 	// Allow future IPIs to be sent on CPU and for task.
 	// Also order this IPI handler against any later manipulations of
 	// the intended task.
-	smp_store_release(&per_cpu(trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
+	smp_store_release(per_cpu_ptr(&trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
 	smp_store_release(&texp->trc_ipi_to_cpu, -1); // ^^^
 }
 
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index a627a200a5ae..f42b98af3ed3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1290,7 +1290,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
 	 */
 	jtsq = READ_ONCE(jiffies_to_sched_qs);
 	ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu);
-	rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu);
+	rnhqp = per_cpu_ptr(&rcu_data.rcu_need_heavy_qs, rdp->cpu);
 	if (!READ_ONCE(*rnhqp) &&
 	    (time_after(jiffies, rcu_state.gp_start + jtsq * 2) ||
 	     time_after(jiffies, rcu_state.jiffies_resched) ||
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index a8d0fcf0826f..677ee3d8671b 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -351,7 +351,7 @@ static void rcu_dump_cpu_stacks(void)
 
 static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
 {
-	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
+	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
 
 	sprintf(cp, "last_accelerate: %04lx/%04lx dyntick_enabled: %d",
 		rdp->last_accelerate & 0xffff, jiffies & 0xffff,

Re: [PATCH] rcu: Use per_cpu_ptr to get the pointer of per_cpu variable

[Neeraj Upadhyay]

On 7/1/2021 10:01 PM, Paul E. McKenney wrote:
> On Thu, Jul 01, 2021 at 08:24:32PM +0530, Neeraj Upadhyay wrote:
>>
>>
>> On 6/30/2021 7:38 PM, Liu Song wrote:
>>> From: Liu Song <liu.song11@zte.com.cn>
>>>
>>> In rcu, most codes have used per_cpu_ptr to obtain per_cpu variable
>>> pointers. This patch adjusts a few codes that have not done so.
>>>
>>
>> Minor: Can we also add below statement?
>> "This patch doesn't introduce any functional change."
>>
>>> Signed-off-by: Liu Song <liu.song11@zte.com.cn>
> 
> Applied with the usual wordsmithing, including adding words to this
> effect, so thank you all!  I removed the obsolete chunk that Neeraj
> pointed out as well.
> 
> Please take a look and check to see if all is well.
> 

Looks good to me

Thanks
Neeraj

> 							Thanx, Paul
> 
> ------------------------------------------------------------------------
> 
> commit 9a6b5a10785f4d9b4f073736e6648fa3851882bd
> Author: Liu Song <liu.song11@zte.com.cn>
> Date:   Wed Jun 30 22:08:02 2021 +0800
> 
>      rcu: Use per_cpu_ptr to get the pointer of per_cpu variable
>      
>      There are a few remaining locations in kernel/rcu that still use
>      "&per_cpu()".  This commit replaces them with "per_cpu_ptr(&)", and does
>      not introduce any functional change..
>      
>      Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
>      Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
>      Signed-off-by: Liu Song <liu.song11@zte.com.cn>
>      Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> 
> diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> index f9f52daacd1c..806160c44b17 100644
> --- a/kernel/rcu/tasks.h
> +++ b/kernel/rcu/tasks.h
> @@ -923,7 +923,7 @@ static void trc_read_check_handler(void *t_in)
>   	// Allow future IPIs to be sent on CPU and for task.
>   	// Also order this IPI handler against any later manipulations of
>   	// the intended task.
> -	smp_store_release(&per_cpu(trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
> +	smp_store_release(per_cpu_ptr(&trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
>   	smp_store_release(&texp->trc_ipi_to_cpu, -1); // ^^^
>   }
>   
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index a627a200a5ae..f42b98af3ed3 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1290,7 +1290,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
>   	 */
>   	jtsq = READ_ONCE(jiffies_to_sched_qs);
>   	ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu);
> -	rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu);
> +	rnhqp = per_cpu_ptr(&rcu_data.rcu_need_heavy_qs, rdp->cpu);
>   	if (!READ_ONCE(*rnhqp) &&
>   	    (time_after(jiffies, rcu_state.gp_start + jtsq * 2) ||
>   	     time_after(jiffies, rcu_state.jiffies_resched) ||
> diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
> index a8d0fcf0826f..677ee3d8671b 100644
> --- a/kernel/rcu/tree_stall.h
> +++ b/kernel/rcu/tree_stall.h
> @@ -351,7 +351,7 @@ static void rcu_dump_cpu_stacks(void)
>   
>   static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
>   {
> -	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
> +	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
>   
>   	sprintf(cp, "last_accelerate: %04lx/%04lx dyntick_enabled: %d",
>   		rdp->last_accelerate & 0xffff, jiffies & 0xffff,
> 

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a 
member of the Code Aurora Forum, hosted by The Linux Foundation

Re: [PATCH] rcu: Use per_cpu_ptr to get the pointer of per_cpu variable

[Uladzislau Rezki]

On Thu, Jul 01, 2021 at 10:35:43PM +0530, Neeraj Upadhyay wrote:
> 
> 
> On 7/1/2021 10:01 PM, Paul E. McKenney wrote:
> > On Thu, Jul 01, 2021 at 08:24:32PM +0530, Neeraj Upadhyay wrote:
> > > 
> > > 
> > > On 6/30/2021 7:38 PM, Liu Song wrote:
> > > > From: Liu Song <liu.song11@zte.com.cn>
> > > > 
> > > > In rcu, most codes have used per_cpu_ptr to obtain per_cpu variable
> > > > pointers. This patch adjusts a few codes that have not done so.
> > > > 
> > > 
> > > Minor: Can we also add below statement?
> > > "This patch doesn't introduce any functional change."
> > > 
> > > > Signed-off-by: Liu Song <liu.song11@zte.com.cn>
> > 
> > Applied with the usual wordsmithing, including adding words to this
> > effect, so thank you all!  I removed the obsolete chunk that Neeraj
> > pointed out as well.
> > 
> > Please take a look and check to see if all is well.
> > 
> 
> Looks good to me
> 
Same to me. Looks good.

There are two dots though in the commit message: "change.." :)

--
Vlad Rezki

Re: [PATCH] rcu: Use per_cpu_ptr to get the pointer of per_cpu variable

[Paul E. McKenney]

On Thu, Jul 01, 2021 at 08:39:33PM +0200, Uladzislau Rezki wrote:
> On Thu, Jul 01, 2021 at 10:35:43PM +0530, Neeraj Upadhyay wrote:
> > 
> > 
> > On 7/1/2021 10:01 PM, Paul E. McKenney wrote:
> > > On Thu, Jul 01, 2021 at 08:24:32PM +0530, Neeraj Upadhyay wrote:
> > > > 
> > > > 
> > > > On 6/30/2021 7:38 PM, Liu Song wrote:
> > > > > From: Liu Song <liu.song11@zte.com.cn>
> > > > > 
> > > > > In rcu, most codes have used per_cpu_ptr to obtain per_cpu variable
> > > > > pointers. This patch adjusts a few codes that have not done so.
> > > > > 
> > > > 
> > > > Minor: Can we also add below statement?
> > > > "This patch doesn't introduce any functional change."
> > > > 
> > > > > Signed-off-by: Liu Song <liu.song11@zte.com.cn>
> > > 
> > > Applied with the usual wordsmithing, including adding words to this
> > > effect, so thank you all!  I removed the obsolete chunk that Neeraj
> > > pointed out as well.
> > > 
> > > Please take a look and check to see if all is well.
> > > 
> > 
> > Looks good to me
> > 
> Same to me. Looks good.
> 
> There are two dots though in the commit message: "change.." :)

Good eyes, fixed, thank you!

							Thanx, Paul

Re: [PATCH] rcu: Use per_cpu_ptr to get the pointer of per_cpu variable

[Joel Fernandes]

On Thu, Jul 1, 2021 at 3:57 PM Paul E. McKenney <paulmck@kernel.org> wrote:
>
> On Thu, Jul 01, 2021 at 08:39:33PM +0200, Uladzislau Rezki wrote:
> > On Thu, Jul 01, 2021 at 10:35:43PM +0530, Neeraj Upadhyay wrote:
> > >
> > >
> > > On 7/1/2021 10:01 PM, Paul E. McKenney wrote:
> > > > On Thu, Jul 01, 2021 at 08:24:32PM +0530, Neeraj Upadhyay wrote:
> > > > >
> > > > >
> > > > > On 6/30/2021 7:38 PM, Liu Song wrote:
> > > > > > From: Liu Song <liu.song11@zte.com.cn>
> > > > > >
> > > > > > In rcu, most codes have used per_cpu_ptr to obtain per_cpu variable
> > > > > > pointers. This patch adjusts a few codes that have not done so.
> > > > > >
> > > > >
> > > > > Minor: Can we also add below statement?
> > > > > "This patch doesn't introduce any functional change."
> > > > >
> > > > > > Signed-off-by: Liu Song <liu.song11@zte.com.cn>
> > > >
> > > > Applied with the usual wordsmithing, including adding words to this
> > > > effect, so thank you all!  I removed the obsolete chunk that Neeraj
> > > > pointed out as well.
> > > >
> > > > Please take a look and check to see if all is well.
> > > >
> > >
> > > Looks good to me
> > >
> > Same to me. Looks good.
> >
> > There are two dots though in the commit message: "change.." :)
>
> Good eyes, fixed, thank you!

LGTM as well, thanks!
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>

Re: [PATCH] rcu: Use per_cpu_ptr to get the pointer of per_cpu variable

[Paul E. McKenney]

On Thu, Jul 01, 2021 at 04:03:58PM -0400, Joel Fernandes wrote:
> On Thu, Jul 1, 2021 at 3:57 PM Paul E. McKenney <paulmck@kernel.org> wrote:
> >
> > On Thu, Jul 01, 2021 at 08:39:33PM +0200, Uladzislau Rezki wrote:
> > > On Thu, Jul 01, 2021 at 10:35:43PM +0530, Neeraj Upadhyay wrote:
> > > >
> > > >
> > > > On 7/1/2021 10:01 PM, Paul E. McKenney wrote:
> > > > > On Thu, Jul 01, 2021 at 08:24:32PM +0530, Neeraj Upadhyay wrote:
> > > > > >
> > > > > >
> > > > > > On 6/30/2021 7:38 PM, Liu Song wrote:
> > > > > > > From: Liu Song <liu.song11@zte.com.cn>
> > > > > > >
> > > > > > > In rcu, most codes have used per_cpu_ptr to obtain per_cpu variable
> > > > > > > pointers. This patch adjusts a few codes that have not done so.
> > > > > > >
> > > > > >
> > > > > > Minor: Can we also add below statement?
> > > > > > "This patch doesn't introduce any functional change."
> > > > > >
> > > > > > > Signed-off-by: Liu Song <liu.song11@zte.com.cn>
> > > > >
> > > > > Applied with the usual wordsmithing, including adding words to this
> > > > > effect, so thank you all!  I removed the obsolete chunk that Neeraj
> > > > > pointed out as well.
> > > > >
> > > > > Please take a look and check to see if all is well.
> > > > >
> > > >
> > > > Looks good to me
> > > >
> > > Same to me. Looks good.
> > >
> > > There are two dots though in the commit message: "change.." :)
> >
> > Good eyes, fixed, thank you!
> 
> LGTM as well, thanks!
> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>

And one more.  ;-)

Again, thank you all!

							Thanx, Paul