Re: Failing back to INSANE timesource :) Time stopped today.

[Maciej W. Rozycki]

On Wed, 14 Apr 2004, Niclas Gustafsson wrote:

> Watching the /proc/interrupts with 10s apart after the "stop".
> 
> [root@s151 root]# more /proc/interrupts
>            CPU0
>   0:   66413955  local-APIC-edge  timer
[...]
> LOC:   67355837
> ERR:          0
> MIS:          0
> [root@s151 root]# more /proc/interrupts
>            CPU0
>   0:   66413955  local-APIC-edge  timer
[...]
> LOC:   67379568
> ERR:          0
> MIS:          0

 This may be because buggy SMM firmware messes with the 8259A (configured
for a transparent mode -- yes that rare "local-APIC-edge" mode is tricky
;-) ) insanely.  You've written this is an IBM box previously -- this 
would be no surprise.  The following patch should help -- I think it's 
already included in the -mm series.

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: macro@xxxxxxxxxxxxx, PGP key available        +

patch-2.6.5-timer_ack-2
--- linux.macro/arch/i386/kernel/io_apic.c	Wed Apr 14 03:57:24 2004
+++ linux/arch/i386/kernel/io_apic.c	Thu Apr 15 14:41:10 2004
@@ -2152,6 +2152,10 @@ static inline void check_timer(void)
 {
 	int pin1, pin2;
 	int vector;
+	unsigned int ver;
+
+	ver = apic_read(APIC_LVR);
+	ver = GET_APIC_VERSION(ver);
 
 	/*
 	 * get/set the timer IRQ vector:
@@ -2165,11 +2169,15 @@ static inline void check_timer(void)
 	 * mode for the 8259A whenever interrupts are routed
 	 * through I/O APICs.  Also IRQ0 has to be enabled in
 	 * the 8259A which implies the virtual wire has to be
-	 * disabled in the local APIC.
+	 * disabled in the local APIC.  Finally timer interrupts
+	 * need to be acknowledged manually in the 8259A for
+	 * do_slow_timeoffset() and for the i82489DX when using
+	 * the NMI watchdog.
 	 */
 	apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);
 	init_8259A(1);
-	timer_ack = 1;
+	timer_ack = !cpu_has_tsc;
+	timer_ack |= nmi_watchdog == NMI_IO_APIC && !APIC_INTEGRATED(ver);
 	enable_8259A_irq(0);
 
 	pin1 = find_isa_irq_pin(0, mp_INT);
@@ -2187,7 +2195,8 @@ static inline void check_timer(void)
 				disable_8259A_irq(0);
 				setup_nmi();
 				enable_8259A_irq(0);
-				check_nmi_watchdog();
+				if (check_nmi_watchdog() < 0)
+					timer_ack = !cpu_has_tsc;
 			}
 			return;
 		}
@@ -2210,7 +2219,8 @@ static inline void check_timer(void)
 				add_pin_to_irq(0, 0, pin2);
 			if (nmi_watchdog == NMI_IO_APIC) {
 				setup_nmi();
-				check_nmi_watchdog();
+				if (check_nmi_watchdog() < 0)
+					timer_ack = !cpu_has_tsc;
 			}
 			return;
 		}
-
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