linux-kernel - Re: [PATCH v2] livepatch: Replace the fake signal sending with TIF_NOTIFY

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Date:   Mon, 29 Mar 2021 09:45:37 -0400
From:   Joe Lawrence <joe.lawrence@...hat.com>
To:     Miroslav Benes <mbenes@...e.cz>, jpoimboe@...hat.com,
        jikos@...nel.org, pmladek@...e.com
Cc:     live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        axboe@...nel.dk
Subject: Re: [PATCH v2] livepatch: Replace the fake signal sending with
 TIF_NOTIFY_SIGNAL infrastructure

On 3/29/21 9:28 AM, Miroslav Benes wrote:
> Livepatch sends a fake signal to all remaining blocking tasks of a
> running transition after a set period of time. It uses TIF_SIGPENDING
> flag for the purpose. Commit 12db8b690010 ("entry: Add support for
> TIF_NOTIFY_SIGNAL") added a generic infrastructure to achieve the same.
> Replace our bespoke solution with the generic one.
> 
> Reviewed-by: Jens Axboe <axboe@...nel.dk>
> Reviewed-by: Petr Mladek <pmladek@...e.com>
> Signed-off-by: Miroslav Benes <mbenes@...e.cz>
> ---
> v2:
> - #include from kernel/signal.c removed [Petr]
> 
>   kernel/livepatch/transition.c | 5 ++---
>   kernel/signal.c               | 4 +---
>   2 files changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
> index f6310f848f34..3a4beb9395c4 100644
> --- a/kernel/livepatch/transition.c
> +++ b/kernel/livepatch/transition.c
> @@ -9,6 +9,7 @@
>   
>   #include <linux/cpu.h>
>   #include <linux/stacktrace.h>
> +#include <linux/tracehook.h>
>   #include "core.h"
>   #include "patch.h"
>   #include "transition.h"
> @@ -369,9 +370,7 @@ static void klp_send_signals(void)
>   			 * Send fake signal to all non-kthread tasks which are
>   			 * still not migrated.
>   			 */
> -			spin_lock_irq(&task->sighand->siglock);
> -			signal_wake_up(task, 0);
> -			spin_unlock_irq(&task->sighand->siglock);
> +			set_notify_signal(task);
>   		}
>   	}
>   	read_unlock(&tasklist_lock);
> diff --git a/kernel/signal.c b/kernel/signal.c
> index f2a1b898da29..604290a8ca89 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -43,7 +43,6 @@
>   #include <linux/cn_proc.h>
>   #include <linux/compiler.h>
>   #include <linux/posix-timers.h>
> -#include <linux/livepatch.h>
>   #include <linux/cgroup.h>
>   #include <linux/audit.h>
>   
> @@ -181,8 +180,7 @@ void recalc_sigpending_and_wake(struct task_struct *t)
>   
>   void recalc_sigpending(void)
>   {
> -	if (!recalc_sigpending_tsk(current) && !freezing(current) &&
> -	    !klp_patch_pending(current))
> +	if (!recalc_sigpending_tsk(current) && !freezing(current))
>   		clear_thread_flag(TIF_SIGPENDING);
>   
>   }
> 

Looks good to me.  Thanks for checking on this and updating.

Acked-by: Joe Lawrence <joe.lawrence@...hat.com>

-- Joe