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SubjectRe: patch to fix set_itimer() behaviour in boundary cases
Matthias Lang <> 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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