Re: [PATCH 3.15 33/37] Fix gcc-4.9.0 miscompilation of load_balance() in scheduler
From: Jakub Jelinek <hidden>
Date: 2014-07-30 07:21:37
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On Wed, Jul 30, 2014 at 09:13:08AM +0200, Markus Trippelsdorf wrote:
On 2014.07.30 at 08:53 +0200, Jakub Jelinek wrote:quoted
On Tue, Jul 29, 2014 at 06:49:09PM -0700, Greg Kroah-Hartman wrote:quoted
3.15-stable review patch. If anyone has any objections, please let me know.IMNSHO this is a too big hammer approach. The bug happened on a single file only (right?), so if anything, IMHO it could be disabled for that single file only, and better do it only for compilers with the bug.No. There are many more files affected. It just happens that Linus analyzed the assembly of this single file (fair.c) and found a bug. Just build your redhat distro kernel with GCC_COMPARE_DEBUG=1 and you'll see. So unless someone analyzes the assembly output of all other affected files by hand and finds no issues, one has to assume the worst.
I'm talking about wrong-code issues. For -fcompare-debug, we indeed check it primarily during gcc bootstrap (through bootstrap-debug) and some testcases, and we'll certainly try to build some more code with -fcompare-debug and fix the issues. Jakub