linux-kernel - Re: [Bug #11342] Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.LFD.1.10.0808260939070.3363@nehalem.linux-foundation.org>
Date:	Tue, 26 Aug 2008 09:51:46 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Yinghai Lu <yhlu.kernel@...il.com>
cc:	Ingo Molnar <mingo@...e.hu>, David Miller <davem@...emloft.net>,
	Alan.Brunelle@...com, travis@....com, tglx@...utronix.de,
	rjw@...k.pl,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	kernel-testers@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	arjan@...ux.intel.com, rusty@...tcorp.com.au
Subject: Re: [Bug #11342] Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c -
 bisected



On Tue, 26 Aug 2008, Yinghai Lu wrote:
> 
> wonder if could use "unsigned long *" directly.

I would actually suggest something like this:

 - we continue to have a magic "cpumask_t".

 - we do different cases for big and small NR_CPUS:

	#if NR_CPUS <= BITS_PER_LONG

	/*
	 * Make it an array - that way passing it as an argument will
	 * always pass it as a pointer!
	 */
	typedef unsigned long cpumask_t[1];

	static inline void create_cpumask(cpumask_t *p)
	{
		*p = 0;
	}
	static inline void free_cpumask(cpumask_t *p)
	{
	}

	#else

	typedef unsigned long *cpumask_t;

	static inline void create_cpumask(cpumask_t *p)
	{
		*p = kcalloc(..);
	}

	static inline void free_cpumask(cpumask_t *p)
	{
		kfree(*p);
	}

	#endif

and now after you do this, you can just do something like

	cpumask_t mycpu;

	create_cpumask(&mycpu);
	..
	free_cpumask(&mycpu);

and in between, you can use 'cpumask' as a pointer, because even when it 
is an array directly allocated on the stack, the array can always 
degenerate into a pointer by C type rules!

And for the small-NR_CPUS case there is zero overhead.

			Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/