linux-kernel - Re: use mutex instead of semaphore in RocketPort driver

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Message-Id: <1179853142.3296.1.camel@laptopd505.fenrus.org>
Date:	Tue, 22 May 2007 09:59:01 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	matthias.kaehlcke@...il.com
Subject: Re: use mutex instead of semaphore in RocketPort driver

>  
> -	down_interruptible(&info->write_sem);
> +	mutex_lock_interruptible(&info->write_mtx);
>  
>  #ifdef ROCKET_DEBUG_WRITE
>  	printk(KERN_INFO "rp_write %d chars...", count);
> @@ -1773,7 +1776,7 @@ end:
>  		wake_up_interruptible(&tty->poll_wait);
>  #endif
>  	}
> -	up(&info->write_sem);
> +	mutex_unlock(&info->write_mtx);
>  	return retval

this code is very very buggy.

mutex_lock_interruptible() may not get the mutex in case a signal
happens... and yet you unlox the mutex unconditionally!!!


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