Date: Sat, 15 Jan 2005 01:36:57 -0800
From: William Lee Irwin III <wli@holomorphy.com>
To: Andrew Morton <akpm@osdl.org>
Cc: matthias@corelatus.se, linux-kernel@vger.kernel.org
Subject: Re: patch to fix set_itimer() behaviour in boundary cases
Message-ID: <20050115093657.GI3474@holomorphy.com>
References: <16872.55357.771948.196757@antilipe.corelatus.se> <20050115013013.1b3af366.akpm@osdl.org>
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Matthias Lang <matthias@corelatus.se> wrote:
>> The linux implementation of setitimer() doesn't behave quite as
>>  expected. I found several problems:
>>    1. POSIX says that negative times should cause setitimer() to 
>>       return -1 and set errno to EINVAL. In linux, the call succeeds.
>>    2. POSIX says that time values with usec >= 1000000 should
>>       cause the same behaviour. In linux, the call succeeds.
>>    3. If large time values are given, linux quietly truncates them
>>       to the maximum time representable in jiffies. On 2.4.4 on PPC,
>>       that's about 248 days. On 2.6.10 on x86, that's about 24 days.
>>       POSIX doesn't really say what to do in this case, but looking at
>>       established practice, i.e. "what BSD does", since the call comes 
>>       from BSD, *BSD returns -1 if the time is out of range.

On Sat, Jan 15, 2005 at 01:30:13AM -0800, Andrew Morton wrote:
> These are things we probably cannot change now.  All three are arguably
> sensible behaviour and do satisfy the principle of least surprise.  So
> there may be apps out there which will break if we "fix" these things.
> If the kernel version was 2.7.0 then well maybe...

We can easily do a "rolling upgrade" by adding new versions of the
system calls, giving glibc and apps grace periods to adjust to them,
and nuking the old versions in a few years.


-- wli
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