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Re: [PATCH] Fix ppc64 test-fenv

From: "Steve Munroe" <sjmunroe at us dot ibm dot com>
To: Jakub Jelinek <jakub at redhat dot com>
Cc: Ulrich Drepper <drepper at redhat dot com>, GNU libc hacker <libc-hacker at sources dot redhat dot com>, "Peter Bergner" <bergner at us dot ibm dot com>
Date: Fri, 11 Apr 2003 14:43:34 -0500
Subject: Re: [PATCH] Fix ppc64 test-fenv

Jakub Jelinek writes

> If the official kernel source contained a buggy prctl so that it is
unsafe
> to try prctl on kernels between 2.4.19 and 2.4.21, then
linux/configure.in
> needs to be changed for 2.4.21 the minimum required kernel version.
> Really, having glibc built without --enable-kernel switch just not work
> forever no matter what kernel it is running on is a bad idea.

prctl is not buggy. It either supports the feature or not. Your patch is OK
and should be integrated.

It just does not correct the fundamental problem. The 2.4.20 kernel does
not
initialize FE0|1 correctly for new processes lwp's. This disables FPE
raise,
until/unless this state is explicitely changed later.

The original fe_nomask.c hack (inherited from PPC32) to set FE0|1 was only
partially reliable on uniprocessors and unreliable on SMPs. That is why we
added the PR_SET_FPEXC feature. I feel that fe_nomask should either work
correctly or return ENOSYS. Your patch prevents test-fenv from seeing a
EINVAL.

The fix (both correct initial state for FE0|1 and the PR_SET_FPEXC feature
are in Marcelo's 2.4.21.pre tree and will be released with 2.4.21.

Follow-Ups:
- Re: [PATCH] Fix ppc64 test-fenv
  - From: Roland McGrath

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