From: Tejun Heo <tj@kernel.org>
To: Eric Sandeen <sandeen@sandeen.net>
Cc: xfs mailing list <xfs@oss.sgi.com>
Subject: Re: stack bloat after stackprotector changes
Date: Wed, 07 Oct 2009 10:32:57 +0900 [thread overview]
Message-ID: <4ACBEFC9.3020707@kernel.org> (raw)
In-Reply-To: <4ACB50C1.80702@sandeen.net>
Hello,
Eric Sandeen wrote:
> Tejun Heo wrote:
>> Eric Sandeen wrote:
>>> It seems that after:
>>>
>>> commit 5d707e9c8ef2a3596ed5c975c6ff05cec890c2b4
>>> Author: Tejun Heo <tj@kernel.org>
>>> Date: Mon Feb 9 22:17:39 2009 +0900
>>>
>>> stackprotector: update make rules
>>>
>>> xfs stack usage jumped up a fair bit;
>>>
>>> Not a lot in each case but could be significant as it accumulates.
>>>
>>> I'm not familiar w/ the gcc stack protector feature; would this be an
>>> expected result?
>>
>> Yeah, it adds a bit of stack usage per each function call and around
>> arrays which seem like they could overflow, so the behavior is
>> expected and I can see it can be a problem with function call depth
>> that deep. Has it caused actual stack overflow?
>>
>> Thanks.
>>
>
> It's hard to point at one thing and say "that caused it" but I did
> overflow (or come very close to it - this one was within 8 bytes).
>
> Add 20 byte or so to each of 65 calls and it starts to matter I guess.
>
> Granted, xfs is being piggy too (as are some of the more common
> functions in the callchain - do_sync_write and write_cache_pages at 320
> bytes each...)
>
> -Eric
>
> Depth Size Location (65 entries)
> ----- ---- --------
> 0) 7280 80 check_object+0x6c/0x1d3
Yeap, that's pretty darn close.
But the thing is that stackprotector is a feature which consumes
certain amount of stack space, so there I'm afraid really isn't a way
around that other than trying to diet the piggies or enlarging the
stack. :-(
Thanks.
--
tejun
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prev parent reply other threads:[~2009-10-07 1:31 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-05 21:01 stack bloat after stackprotector changes Eric Sandeen
2009-10-06 5:53 ` Tejun Heo
2009-10-06 14:14 ` Eric Sandeen
2009-10-07 1:32 ` Tejun Heo [this message]
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