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SubjectRe: [RFC] Recursive printk
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



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