Timer_irq_works() calls mdelay(10) to delay ten ticks and checks whether
the timer IRQ works or not. The mdelay() depends on the loops_per_jiffy
which is set up in calibrate_delay().
Timer_irq_works() has been in advance of calibrate_delay(). the mdelay()
doesn't work well in timer_irq_works().
Refactor the delay logic by replace the mdelay() with __delay() and
regard 2**MAX_BAND as the maximum threshold of CPU frequency.
Signed-off-by: Dou Liyang <douly.f...@cn.fujitsu.com>
---
arch/x86/kernel/apic/io_apic.c | 47 ++++++++++++++++++++++++++++++++++++------
1 file changed, 41 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 347bb9f..d3b0268 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1608,6 +1608,18 @@ static int __init notimercheck(char *s)
__setup("no_timer_check", notimercheck);
/*
+ * The loops_per_jiffy is not be set, udelay() or mdelay() cannot
+ * be called here.
+ * Set 16GHZ(loops_per_jiffy almost is 2**24) as the maximum threshold
+ * of CPU frequency. Exceed the threshold indicates the timer interrupt
+ * doesn't work.
+ *
+ * FIXME: Explore a new way to check the timer interrupt work.
+ */
+
+#define MAX_BAND 24
+
+/*
* There is a nasty bug in some older SMP boards, their mptable lies
* about the timer IRQ. We do the following to work around the situation:
*
@@ -1617,28 +1629,51 @@ __setup("no_timer_check", notimercheck);
*/
static int __init timer_irq_works(void)
{
- unsigned long t1 = jiffies;
+ unsigned long ticks;
unsigned long flags;
+ /* Set up approx 2 Bo*oMips to start */
+ int band = 11;
+ int loop_times;
if (no_timer_check)
return 1;
local_save_flags(flags);
local_irq_enable();
- /* Let ten ticks pass... */
- mdelay((10 * 1000) / HZ);
- local_irq_restore(flags);
+ /*
+ * Estimate the loops in (1,2] jiffies.
+ *
+ * After the loops (2**12+2**13+...+2**MAX_BAND) times,
+ * if time_before(jiffies, ticks + 2) is also n, That the
+ * timer interrupt did not work, return 0.
+ */
+ ticks = jiffies;
+ do {
+ if (band++ == MAX_BAND) {
+ local_irq_restore(flags);
+ return 0;
+ }
+
+ __delay(1 << band);
+ } while (time_before(jiffies, ticks + 2));
/*
* Expect a few ticks at least, to be sure some possible
* glue logic does not lock up after one or two first
* ticks in a non-ExtINT mode. Also the local APIC
- * might have cached one ExtINT interrupt. Finally, at
+ * might have cached one ExtINT interrupt. Finally, at
* least one tick may be lost due to delays.
+ *
+ * As 2**12+2**13+...+2**band < 2**(1 + band),
+ * it certainly delayed for more than 4 ticks.
*/
+ for (loop_times = 0; loop_times < 4; loop_times++)
+ __delay(1 << (1 + band));
+
+ local_irq_restore(flags);
/* jiffies wrap? */
- if (time_after(jiffies, t1 + 4))
+ if (time_after(jiffies, ticks + 4))
return 1;
return 0;
}
--
2.5.5
