linux-kernel - Re: [PATCH 2/6] kernel: add task

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Date:   Thu, 8 Oct 2020 14:58:32 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-kernel@...r.kernel.org, io-uring@...r.kernel.org,
        peterz@...radead.org, tglx@...utronix.de
Subject: Re: [PATCH 2/6] kernel: add task_sigpending() helper

On 10/05, Jens Axboe wrote:
>
>  static inline int signal_pending_state(long state, struct task_struct *p)
>  {
>  	if (!(state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL)))
>  		return 0;
> -	if (!signal_pending(p))
> +	if (!task_sigpending(p))
>  		return 0;

This looks obviously wrong. Say, schedule() in TASK_INTERRUPTIBLE should
not block if TIF_NOTIFY_SIGNAL is set.

With this change set_notify_signal() will not force the task to return
from wait_event_interruptible, mutex_lock_interruptible, etc.

>  	return (state & TASK_INTERRUPTIBLE) || __fatal_signal_pending(p);
> @@ -389,7 +394,7 @@ static inline bool fault_signal_pending(vm_fault_t fault_flags,
>  {
>  	return unlikely((fault_flags & VM_FAULT_RETRY) &&
>  			(fatal_signal_pending(current) ||
> -			 (user_mode(regs) && signal_pending(current))));
> +			 (user_mode(regs) && task_sigpending(current))));

This looks unnecessary,

> @@ -773,7 +773,7 @@ static int ptrace_peek_siginfo(struct task_struct *child,
>  		data += sizeof(siginfo_t);
>  		i++;
>  
> -		if (signal_pending(current))
> +		if (task_sigpending(current))

This too.

IMO, this patch should do s/signal_pending/task_sigpending/ only if it is
strictly needed for correctness.

Oleg.