id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	field_blocks	field_dependson	field_seealso
220	Unexpected FPU exception in top utility	Stanislav Kozina		"Sometimes I got FPU exception (number 16) when computing percentages using floating point instruction in `top' utility.

The exception was detected when running on two ia32 CPUs under qemu-kvm simulator, using one CPU there was no problem. But the exception depends on many other things - changing message echoed by printf on very different place can change if the FPU exception rises or not.

There is a branch to preserve this behaviour:
lp:~ersin/helenos/fpu-bug

In the branch there is the skeleton of the `top' utility, which still sometimes emits the exception. If you get this branch, compile, run system (rather on pair ia32 CPUs), run `top' and press few keys on the keyboard, you should get the exception.

The `top' utility still retrieves some data from kernel, but these are just to get some random numbers. You can replace them with hardcoded values, but then you have to compile `top' with -O0 flag, otherwise compiler removes FPU computation at all.

The only other thing, which still remains in the code, is the `tgetchar' method, which was copied from `tetris'. This one probably really causes the exception, because without it I was not able to get it."	defect	closed	major	0.4.3	helenos/kernel/ia32	mainline	worksforme	fpu