Hi,
On Fri, Jun 23, 2006 at 03:40:25AM -0400, Chuck Ebbert wrote:
> Add cpu_relax() to infinite loops in crash.c and
> doublefault.c. This is the safest change.
Thanks for your continued work on this!
What's the reasoning for not running halt() in doublefault_fn()?
In order to consolidate those places to safely halt a CPU,
I could think of (possibly in a header file):
/* very, very safely halt CPU:
- do minimal checking in case CPU might already be overheated (unreliable!)
(also use inlining to avoid call overhead on an unreliable CPU)
- try to use halt() and cpu_relax() very liberally to keep the crashed
CPU as cool as possible (crash might have happened due to CPU fan failure!)
While ACPI specifies CPU shutdown on over-temperature, we really don't
want to rely on this since it might be broken or we simply don't use ACPI
mode at all...
*/
inline void safely_halt_cpu(int do_minimal_checking)
{
/* inlining will optimize the branching away */
if (!do_minimal_checking) {
if (cpu_data[smp_processor_id()].hlt_works_ok)
for (;;) {
halt();
/* halt failed? still make sure to cpu_relax()! */
cpu_relax();
}
else
for (;;) {
cpu_relax();
cpu_relax();
cpu_relax();
}
} else {
halt();
/* halt didn't work, so still keep as cool as possible: */
for (;;) {
cpu_relax();
cpu_relax();
cpu_relax();
}
}
}
Does my preliminary code even make any sense at all? ;)
Might want to cleverly rearrange it to try to get rid of the cpu_relax()
duplication while not abandoning any advantage of those different
conditions.
Andreas Mohr
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