|To:||Muthu Kumaran <email@example.com>|
|Subject:||Re: Switch FPU emulator trap to BREAK instruction|
|From:||David Daney <firstname.lastname@example.org>|
|Date:||Fri, 05 Feb 2010 09:36:20 -0800|
|User-agent:||Thunderbird 188.8.131.52 (X11/20090320)|
Muthu Kumaran wrote:
I am using 2.6.18 linux version on MIPS32 core. One of the application is using intensive floating point operations. This hardware doesn't have FPU and also the application is not compiled for software floating point support. Hence, it is using the floating point emulation. While running that application, On a timer interrupt there is a normal integer div instruction which gives wrong result in the HI register. However, when I applied the following patch, this problem disappeared. http://kerneltrap.org/mailarchive/git-commits-head/2008/10/30/3873324 When I looked into the patch, handling of invalid instruction exception is moved from trap to break.
Incorrect analysis. It was changed from an Adress Error (ADE) exception to a BREAK.
There is no other behavioural change in this patch. I really don't understand the need for this patch, May I ask someone to explain the background information behind this patch? Is this for any known issue?
The change log states the reason. FPU emulator delay slot emulation was failing on some systems.
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