buildworld panic on ia64
xcllnt at mac.com
Wed Jul 8 16:26:15 UTC 2009
On Jul 8, 2009, at 4:49 AM, Anton Shterenlikht wrote:
> On Tue, Jul 07, 2009 at 05:29:06PM -0700, Marcel Moolenaar wrote:
>> On Jul 7, 2009, at 6:36 AM, Rink Springer wrote:
>>>> I tried to reproduce the error, got this on the way:
>>>> # XXX: bogusly disabled high FP regs
>>> I get this message quite often as well; I intend to figure out
>>> going on. Marcel, if you have any idea, please let me know.
>> It's a race condition. The high FP registers are lazily
>> context-switched and this error is emitted when a thread
>> wants to use the high FP registers when they are disabled
>> and the CPU onto which the thread is running has the high
>> FP registers corresponding to that thread in registers.
>> In that scenario the high FP registers should not even be
>> In the above case the kernel simply enables the high FP
>> registers and continues the thread. For the most part the
>> condition is harmless, but I've been looking at a panic
>> that's the result of inconsistency in the high FP state,
>> so the race is potentially fatal.
>> BTW: I never got the error when doing a buildworld. I
>> think Anton's non-standard compiler options make GCC much
>> more FP intensive and thus prone to causing the race.
> Marcel, sorry, I probably misunderstood "compiler options"
> in the previous reply. Did you mean -j option in
> make -j10 buildworld?
-j is a make option. Modulo the FP race you're perfectly fine
with any -j value that matches the number of CPUs in your box
(with 4xNCPUS a rule-of-thumb maximum probably).
If the compiler isn't FP intensive, then even -j128 on a dual-
CPU box is not causing you problems (it's pointless though :-)
xcllnt at mac.com
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