linux-kernel - Re: [tip:perf/core] perf/x86: Add generic Intel uncore PMU support

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: <4FE3A9DF.20303@zytor.com>
Date:	Thu, 21 Jun 2012 16:10:23 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	mingo@...nel.org, linux-kernel@...r.kernel.org,
	a.p.zijlstra@...llo.nl, torvalds@...ux-foundation.org,
	zheng.z.yan@...el.com, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/core] perf/x86: Add generic Intel uncore PMU support

On 06/21/2012 03:51 PM, Andrew Morton wrote:
> 
> What *is* significant is the effect of a signedness change upon
> arithmetic, conversions, warnings, etc.  And whether such a change
> might actually introduce bugs.
> 
> 
> Back away and ask the broader questions: why did ktime_t choose
> unsigned?  Is time a signed concept?  What is the right thing to do
> here, from a long-term design perspective?

Time is definitely a signed concept -- it has no beginning or end (well,
the Big Bang, but the ±110 Myr or so uncertainty of the exact timing of
the Big Bang makes it a horridly awkward choice for epoch.)

Now, for some users of time you can inherently guarantee there will
never be any references to time before a particular event, e.g. system
boot, in which case an unsigned number might make sense, but as a whole
I think using a signed type as time_t in nearly all Unix implementation
was The Right Thing.

	-hpa
--
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/