From: Willy Tarreau <w@1wt.eu>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Andrew <nick@nick-andrew.net>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Takashi Iwai <tiwai@suse.de>
Subject: Re: [RFC] Recursive printk
Date: Sat, 6 Dec 2008 08:33:05 +0100 [thread overview]
Message-ID: <20081206073304.GE24654@1wt.eu> (raw)
In-Reply-To: <20081205232016.366765e2.akpm@linux-foundation.org>
On Fri, Dec 05, 2008 at 11:20:16PM -0800, Andrew Morton wrote:
> > void snd_verbose_printk(const char *file, int line, const char *format, ...)
> > {
> > va_list args;
> >
> > if (format[0] == '<' && format[1] >= '0' && format[1] <= '7' && format[2] == '>') {
> > char tmp[] = "<0>";
> > tmp[1] = format[1];
> > printk("%sALSA %s:%d: ", tmp, file, line);
> > format += 3;
>
> That's racy. Two threads can fight over tmp[1]. It should do:
>
> printk("<%c>ALSA %s:%d: ", format[1], tmp, file, line);
>
> (I didn't know that you can even modify literal strings - shouldn't
> they be in read-only storage?)
no Andrew, this tmp[] is declared on the stack, and gcc emits code to
copy the constant "<0>" onto the stack every time this code is called
(which is basically just a 32-bit integer copy). So there's no race
either.
Regards,
Willy
next prev parent reply other threads:[~2008-12-06 7:33 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-06 6:59 [RFC] Recursive printk Nick Andrew
2008-12-06 6:59 ` [RFC PATCH v1 1/3] Split the vsnprintf function into two parts Nick Andrew
2008-12-06 7:00 ` [RFC PATCH v1 2/3] Add %v support to vsnprintf() Nick Andrew
2008-12-06 17:27 ` Linus Torvalds
2008-12-06 7:00 ` [RFC PATCH v1 3/3] Sample refactor of socket.c to use recursive printk Nick Andrew
2008-12-06 7:03 ` David Miller
2008-12-06 7:18 ` Valdis.Kletnieks
2008-12-06 7:40 ` Nick Andrew
2008-12-06 7:20 ` [RFC] Recursive printk Andrew Morton
2008-12-06 7:33 ` Willy Tarreau [this message]
2008-12-06 7:41 ` Andrew Morton
2008-12-06 8:16 ` Willy Tarreau
2008-12-06 9:43 ` Takashi Iwai
2008-12-06 7:42 ` Joe Perches
2008-12-06 8:40 ` Nick Andrew
2008-12-06 9:11 ` Joe Perches
2008-12-06 23:16 ` Nick Andrew
2008-12-06 23:24 ` Linus Torvalds
2008-12-06 19:35 ` Al Viro
2008-12-06 8:30 ` Nick Andrew
2008-12-08 1:42 ` Tejun Heo
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