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Message-Id: <1190378737.30016.15.camel@gilboa-home-dev.localdomain>
Date: Fri, 21 Sep 2007 14:45:37 +0200
From: Gilboa Davara <gilboad@...il.com>
To: Paulo Marques <pmarques@...popie.com>
Cc: Satyam Sharma <satyam@...radead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Reduce __print_symbol/sprint_symbol stack usage.
Hello Paulo,
[snip]
> I must say I agree with Satyam here.
>
> Locking in the panic path might leave us without some critical debug
> information, which is much more important than all this.
>
> Maybe it would be better to change the print_symbol interface to avoid
> having a "char buffer[KSYM_SYMBOL_LEN];" at all.
>
> Most print_symbol callers use something like "yada yada %s" as the
> format string, with an optional "\n" in the end.
>
> if we change the interface from "print_symbol(fmt, addr)" to
> "print_symbol(prefix, addr, int newline)" we can simply do:
>
> printk(prefix);
> printk_symbol(addr);
> if (newline)
> printk("\n");
>
> where "printk_symbol" is a new function that does the same as
> sprint_symbol, but does "printk" instead of "sprintf".
>
> This should reduce immensely the stack usage of print_symbol without the
> need for locking.
I fully agree.
... Further more, multiple printk_symbols should be combined into a
single, multi-line printk transaction. (To prevent debug printk's from
trashing a BUG() dump_stack).
>
> Of course this requires changing _all_ callers of print_symbol to use
> the new interface, but these are less than 100 ;)
This is my first contribution to the Linux kernel. As such I rather
start small, and work my way up slowly. (Read: solve the immediate stack
over-run now, think about changing the symbol_display interface later)
>
> Comments?
I do agree that the current interface needs work.
... But as I said, I rather start slowly and on small scale. (Though I
did find a rather problematic place to start at... ;))
- Gilboa
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