Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()"

From	Willy Tarreau <w@1wt.eu>
Newsgroups	linux.kernel
Subject	Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()"
Date	2015-11-23 18:00 +0100
Message-ID	<qy2D9-4un-49@gated-at.bofh.it> (permalink)
References	<qy2a7-4i0-43@gated-at.bofh.it> <qy2jN-4lG-31@gated-at.bofh.it> <qy2jN-4lG-45@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Mon, Nov 23, 2015 at 04:37:50PM +0000, Russell King - ARM Linux wrote:
> On Mon, Nov 23, 2015 at 05:33:59PM +0100, Willy Tarreau wrote:
> > I think you could do better by simply calling panic("BUG!") instead as
> > BUG() does. It will avoid the printk() call and pushing the file/line
> > number onto the stack. It will also probably not inflate the rodata this
> > way.
> 
> Does that not depend on the architectures BUG() implementation?  If an
> architecture implements it as a signalling illegal instruction and a
> lookup table, changing it to be a panic() would probably be more code.

That's a very good point, I didn't think about it and yes I think you're
right then (eg: when CONFIG_DEBUG_BUGVERBOSE is not set, x86 and arm will
only emit a single instruction).

Best regards,
Willy

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Thread

[RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Arnd Bergmann <arnd@arndb.de> - 2015-11-23 17:30 +0100
  Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Willy Tarreau <w@1wt.eu> - 2015-11-23 17:40 +0100
    Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-11-23 17:40 +0100
      Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Arnd Bergmann <arnd@arndb.de> - 2015-11-23 18:00 +0100
        Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Willy Tarreau <w@1wt.eu> - 2015-11-23 18:10 +0100
        Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-11-23 18:30 +0100
          Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Arnd Bergmann <arnd@arndb.de> - 2015-11-23 20:40 +0100
      Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Willy Tarreau <w@1wt.eu> - 2015-11-23 18:00 +0100
  Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-11-23 17:40 +0100
  Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Josh Triplett <josh@joshtriplett.org> - 2015-11-23 21:30 +0100
    Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Arnd Bergmann <arnd@arndb.de> - 2015-11-23 22:00 +0100
      Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Josh Triplett <josh@joshtriplett.org> - 2015-11-23 22:20 +0100
        Re: [RFC] asm-generic: default BUG_ON(x) to "if(x) BUG()" Arnd Bergmann <arnd@arndb.de> - 2015-11-23 22:40 +0100

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