linux-kernel - Re: [PATCH V2 7/9] fork: Add worker flag to ignore signals

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Date:   Wed, 22 Sep 2021 14:52:36 +0200
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Mike Christie <michael.christie@...cle.com>
Cc:     hdanton@...a.com, hch@...radead.org, stefanha@...hat.com,
        jasowang@...hat.com, mst@...hat.com, sgarzare@...hat.com,
        virtualization@...ts.linux-foundation.org, axboe@...nel.dk,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 7/9] fork: Add worker flag to ignore signals

On Tue, Sep 21, 2021 at 04:52:16PM -0500, Mike Christie wrote:
> The kthread API creates threads that ignore all signals by default so
> modules like vhost that will move from that API to kernel_worker will
> not be expecting them. This patch adds a worker flag that tells
> kernel_worker to setup the task to ignore signals.
> 
> Signed-off-by: Mike Christie <michael.christie@...cle.com>
> ---

Looks good,
Acked-by: Christian Brauner <christian.brauner@...ntu.com>

>  include/linux/sched/task.h |  1 +
>  kernel/fork.c              | 11 ++++++++++-
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
> index 781abbc1c288..aefa0d221b57 100644
> --- a/include/linux/sched/task.h
> +++ b/include/linux/sched/task.h
> @@ -21,6 +21,7 @@ struct css_set;
>  #define KERN_WORKER_IO		BIT(0)
>  #define KERN_WORKER_USER	BIT(1)
>  #define KERN_WORKER_NO_FILES	BIT(2)
> +#define KERN_WORKER_NO_SIGS	BIT(3)
>  
>  struct kernel_clone_args {
>  	u64 flags;
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 3f3fcabffa5f..34d3dca70cfb 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -2555,6 +2555,8 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
>  struct task_struct *kernel_worker(int (*fn)(void *), void *arg, int node,
>  				  unsigned long clone_flags, u32 worker_flags)
>  {
> +	struct task_struct *tsk;
> +
>  	struct kernel_clone_args args = {
>  		.flags		= ((lower_32_bits(clone_flags) | CLONE_VM |
>  				   CLONE_UNTRACED) & ~CSIGNAL),
> @@ -2564,7 +2566,14 @@ struct task_struct *kernel_worker(int (*fn)(void *), void *arg, int node,
>  		.worker_flags	= KERN_WORKER_USER | worker_flags,
>  	};
>  
> -	return copy_process(NULL, 0, node, &args);
> +	tsk = copy_process(NULL, 0, node, &args);
> +	if (IS_ERR(tsk))
> +		return tsk;
> +
> +	if (worker_flags & KERN_WORKER_NO_SIGS)
> +		ignore_signals(tsk);
> +
> +	return tsk;
>  }
>  EXPORT_SYMBOL_GPL(kernel_worker);
>  
> -- 
> 2.25.1
>