linux-kernel - Re: [PATCH] MN10300: Fix the PERCPU() alignment to allow for workqueues

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]

Date:	Tue, 26 Oct 2010 16:56:49 +0200
From:	Tejun Heo <tj@...nel.org>
To:	David Howells <dhowells@...hat.com>
CC:	torvalds@...l.org, akpm@...ux-foundation.org,
	linux-am33-list@...hat.com, linux-kernel@...r.kernel.org,
	Akira Takeuchi <takeuchi.akr@...panasonic.com>,
	Mark Salter <msalter@...hat.com>
Subject: Re: [PATCH] MN10300: Fix the PERCPU() alignment to allow for workqueues

Hello, David.

On 10/26/2010 04:50 PM, David Howells wrote:
>>> FRV's page size is 16KB, so on that we really don't want it to be
>>> PAGE_SIZE.
>>
>> Why not?  It's in the init section which will be freed anyway and with
>> the kernel image compression it's not even gonna add any noticeable
>> amount to the kernel image size.  There isn't any benefit in using
>> anything smaller than PAGE_SIZE for alignment.  Also, percpu allocator
>> guarantees alignment requirement upto PAGE_SIZE is honored.  If the
>> output section uses smaller alignment, the percpu AS will end up being
>> misaligned.
> 
> The bootloader we have doesn't do decompression.

I see.  :-(

> On the other hand, does the PERCPU stuff need to be allocated space
> in the image by the linker?  Can it be initialised to anything other
> than zeros?

Sure, for example, in kernel/timer.c.

  static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;

It doesn't seem too popular at this point tho.

Thanks.

-- 
tejun
--
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/