Messages in this thread | | | Date | Tue, 20 Jun 2006 09:50:15 +0200 | From | Andreas Mohr <> | Subject | Re: [patch] i386: halt the CPU on serious errors |
| |
Hi,
On Tue, Jun 20, 2006 at 12:55:25AM -0400, Chuck Ebbert wrote: > Halt the CPU when serious errors are encountered and we > deliberately go into an infinite loop. > > Suggested by Andreas Mohr.
Thanks for the very fast patch, but:
> /* Assume hlt works */ > - halt(); > - for(;;); > + for (;;) > + halt();
The comment above seems to hint at this code in arch/i386/kernel/smp.c/ stop_this_cpu() which does proper hlt checks:
if (cpu_data[smp_processor_id()].hlt_works_ok) for(;;) halt(); for (;;);
So I'm unsure what happens if hlt is not supported properly. Maybe there's an invalid opcode exception in a loop then.
I think a patch should do the following (or more):
- try to group various CPU emergency stop places together - comment about trying to avoid overheating, mentioning ACPI thermal protection specifications and possibly *missing protection* in non-ACPI systems/modes (APM!) - if (hlt_works_ok), do hlt loop - if not, do a cpu_relax() loop (or even: for (;;) 3 times cpu_relax() for lower activity?)
One thing that may be worth pondering about is whether using cpu_relax() might actually keep the CPU slightly below the ACPI shutdown temperature limit and thus do *more* harm with a broken fan. In that case we might want to check for active ACPI mode and if active do a busy loop instead. This however may cause temperature to cycle (will a CPU shutdown reactivate itself after cooling down again?), so a cpu_relax() might still be better.
Andreas Mohr - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |