Re: [PATCH] Reduce stack used by lib/hexdump.c

Andrew Morton
2007-12-06T07:11:44Z

On Thu, 6 Dec 2007 00:58:38 -0500 Kyle Moffett <mrmacman_g4@mac.com> wrote:

> On Dec 05, 2007, at 21:42:35, Joe Perches wrote:
> > On Wed, 2007-12-05 at 18:18 -0800, Randy Dunlap wrote:
> >> Joe Perches wrote:
> >>> Maybe just eliminate the 16 or 32 byte width option and force it
> >>> to only 16 byte widths.
> >> Have you checked users (callers)? I'm pretty sure that one of the
> >> callers wanted 32 and that's why it's there.
> >
> > I did. There is only 1 subsystem. That's easy to change.
> >
> > drivers/mtd/ubi/debug.c: print_hex_dump(KERN_DEBUG, "",
> > DUMP_PREFIX_OFFSET, 32, 1,
> > drivers/mtd/ubi/io.c: print_hex_dump(KERN_DEBUG, "",
> > DUMP_PREFIX_OFFSET, 32, 1,
> >
> > Long lines in the log file are not too easy to read anyway. Using
> > 16 byte dumps per line instead of 32 isn't painful.
> >
> > It gets rid of the allocation, reduces the argument count and makes
> > the kernel smaller. I think it's all good.
> >
> > Every current caller would have to change though.
>
> Alternatively, since print_hex_dump is not a performance-critical
> path (and usually indicates an error/debug condition), you could
> probably just make a static "hexdump_lock" spinlock and
> spin_lock_irqsave()/spin_unlock_irqrestore(). It would always nest
> inside any other lock (except during crash, where we break locks
> already for printk()), and I doubt any of the callers would notice
> the serialization since they're already serialized on the printk buffer.
>

Yup, that'd work.