User: Password:
|
|
Subscribe / Log in / New account

Re: [RFC] timers, pointers to functions and type safety

From:  Ingo Molnar <mingo-AT-elte.hu>
To:  Al Viro <viro-AT-ftp.linux.org.uk>
Subject:  Re: [RFC] timers, pointers to functions and type safety
Date:  Mon, 4 Dec 2006 12:48:51 +0100
Cc:  Thomas Gleixner <tglx-AT-linutronix.de>, Matthew Wilcox <matthew-AT-wil.cx>, Linus Torvalds <torvalds-AT-osdl.org>, linux-arch-AT-vger.kernel.org, linux-kernel-AT-vger.kernel.org
Archive-link:  Article, Thread


* Al Viro <viro@ftp.linux.org.uk> wrote:

> > This is going to make a lot of data structures smaller, when the 
> > timer_list is embedded in the structure itself and for the lot, 
> > which ignores the timer callback argument anyway.
> 
> container_of => still lousy type safety.  All over the sodding place.

the question is: which is more important, the type safety of a 
container_of() [or type cast], which if we get it wrong produces a 
/very/ trivial crash that is trivial to fix - or embedded timers data 
structure size all around the kernel? I believe the latter is more 
important.

and we could have a runtime debugging option to tie the type of the 
structure to the timer list entry. For example by using 
__builtin_classify_type(), sizeof() and offsetof() to fingerprint timer 
structs at init_timer time, and then checking for that at container_of() 
time - or something like that. In fact, gcc should really give us a 
better way to categorize types than __builtin_classify_type(). We could 
probably improve the situation by having some global registry of types 
known to the kernel, via a huge switch() around 
__builtin_types_compatible_p().

	Ingo


(Log in to post comments)


Copyright © 2006, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds