On ���, 2001-12-17 at 06:34, Dave Jones wrote:
> On 16 Dec 2001, Borsenkow Andrej wrote:
>
> > I thought once about run-time detection - if BIOS reports that Idle does
> > not slow down CPU try Idle call once and compare jiffies (probably
> > repeat several times to be sure). Is it sensible?
>
> A far simpler way would be to add DMI blacklist entries for the BIOSes
> that don't do this, although this assumes the problem machine has a DMI
> compliant BIOS.
>
Well, the following three-liners (+ comments) seems to do it. It checks
if clock was advanced after return from APM Idle - if not we assume BIOS
did not halt CPU and do it ourselves. The addidional condition &&
!current->need_resched is for the case when BIOS did halt CPU and
non-clock interrupt happened that waked up somebody else. But may be I
am just plain paranoid. The code has no impact for "BIOS slows CPU"
case.
It works here for broken BIOS. I appreciate if people with good BIOS
test it.
-andrej
--- apm.c.bor Tue Dec 18 20:30:08 2001
+++ apm.c Tue Dec 18 20:42:24 2001
@@ -1381,13 +1381,18 @@
*/
if (apm_do_idle() != -1) {
unsigned long start = jiffies;
+ unsigned long before;
while ((!exit_kapmd) && system_idle()) {
- if (apm_do_idle()) {
+ before = jiffies;
+ if (apm_do_idle() || (jiffies == before && !current->need_resched)) {
set_current_state(TASK_INTERRUPTIBLE);
/* APM needs us to snooze .. either
the BIOS call failed (-1) or it
slowed the clock (1). We sleep
- until it talks to us again */
+ until it talks to us again.
+ If clock did not advance CPU was
+ not halted by BIOS so we do it
+ now*/
schedule_timeout(1);
}
if ((jiffies - start) > APM_CHECK_TIMEOUT) {
