linux-kernel - Re: [PATCH v2] trace/pid_list: Change gfp flags in pid_list_fill

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Message-Id: <20240705231112.4097fd46656778115acf7da1@kernel.org>
Date: Fri, 5 Jul 2024 23:11:12 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Levi Yun <yeoreum.yun@....com>
Cc: rostedt@...dmis.org, mathieu.desnoyers@...icios.com,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH v2] trace/pid_list: Change gfp flags in
 pid_list_fill_irq()

On Thu,  4 Jul 2024 16:02:26 +0100
Levi Yun <yeoreum.yun@....com> wrote:

> From: "levi.yun" <yeoreum.yun@....com>
> 
> pid_list_fill_irq() runs via irq_work.
> When CONFIG_PREEMPT_RT is disabled, it would run in irq_context.
> so it shouldn't sleep while memory allocation.
> 
> Change gfp flags from GFP_KERNEL to GFP_NOWAIT to prevent sleep in
> irq_work.
> 
> This change wouldn't impact functionality in practice because the worst-size
> is 2K.
> 

Looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

and 

Fixes: 8d6e90983ade ("tracing: Create a sparse bitmask for pid filtering")

Thank you,

> Signed-off-by: levi.yun <yeoreum.yun@....com>
> ---
>  kernel/trace/pid_list.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/pid_list.c b/kernel/trace/pid_list.c
> index 95106d02b32d..85de221c0b6f 100644
> --- a/kernel/trace/pid_list.c
> +++ b/kernel/trace/pid_list.c
> @@ -354,7 +354,7 @@ static void pid_list_refill_irq(struct irq_work *iwork)
>  	while (upper_count-- > 0) {
>  		union upper_chunk *chunk;
> 
> -		chunk = kzalloc(sizeof(*chunk), GFP_KERNEL);
> +		chunk = kzalloc(sizeof(*chunk), GFP_NOWAIT);
>  		if (!chunk)
>  			break;
>  		*upper_next = chunk;
> @@ -365,7 +365,7 @@ static void pid_list_refill_irq(struct irq_work *iwork)
>  	while (lower_count-- > 0) {
>  		union lower_chunk *chunk;
> 
> -		chunk = kzalloc(sizeof(*chunk), GFP_KERNEL);
> +		chunk = kzalloc(sizeof(*chunk), GFP_NOWAIT);
>  		if (!chunk)
>  			break;
>  		*lower_next = chunk;
> --
> LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
> 
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>