Messages in this thread Patch in this message | | | From | Borsenkow Andrej <> | Subject | PATCH: apm.c - detection of brokern APM Idle call implementation | Date | 18 Dec 2001 20:54:47 +0300 |
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On Пнд, 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) { | |