linux-kernel - Re: [PATCH] Fix logical and operator at interrupt handler thread

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Date:	Wed, 01 Feb 2012 06:41:31 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Geunsik Lim <geunsik.lim@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Fix logical and operator at interrupt handler thread

Le mercredi 01 février 2012 à 14:19 +0900, Geunsik Lim a écrit :
> From: Geunsik Lim <geunsik.lim@...sung.com>
> 
> '&' is a bitwise operation. (e.g: a & b )
> Use '&&' and-operator instead of '&' bitwise operator.
> 
> Signed-off-by: Geunsik Lim <geunsik.lim@...sung.com>
> ---
>  kernel/irq/manage.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index a9a9dbe..c0730ad 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -773,7 +773,7 @@ static int irq_thread(void *data)
>  			struct irqaction *action);
>  	int wake;
>  
> -	if (force_irqthreads & test_bit(IRQTF_FORCED_THREAD,
> +	if (force_irqthreads && test_bit(IRQTF_FORCED_THREAD,
>  					&action->thread_flags))
>  		handler_fn = irq_forced_thread_fn;
>  	else


This was intentional, to have a single conditional move :

ffffffff810b0868:       0f b6 15 19 f5 bd 00    movzbl 0xbdf519(%rip),%edx        # ffffffff81c8fd88 <force_irqthreads>
ffffffff810b086f:       49 89 c5                mov    %rax,%r13
ffffffff810b0872:       48 8b 43 40             mov    0x40(%rbx),%rax
ffffffff810b0876:       be 01 00 00 00          mov    $0x1,%esi
ffffffff810b087b:       48 c1 e8 04             shr    $0x4,%rax
ffffffff810b087f:       85 c2                   test   %eax,%edx
ffffffff810b0881:       48 c7 c0 80 0a 0b 81    mov    $0xffffffff810b0a80,%rax
ffffffff810b0888:       48 c7 c2 40 dc 80 81    mov    $0xffffffff8180dc40,%rdx
ffffffff810b088f:       4c 0f 44 f8             cmove  %rax,%r15


I guess you could instead use jump_label here to shorten the code.




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