Philippe Gerum wrote:
> On Sun, 2006-07-09 at 18:56 +0200, Jan Kiszka wrote:
> > I can confirm the failing NMI test here on my notebook with both nucleus
> > and native skin built into the kernel. I haven't seen false positive
> > NMIs yet, but the tracer is still on. Will switch off and re-check.
>
> FWIW, here, the false positive is raised immediately when starting the
> latency test.
The attached patch attempt to workaround these early shots, count them,
and display them in /proc/xenomai/nmi_early_shots. Could you try it on
your box and see if the /proc display moves ?
--
Gilles Chanteperdrix.
Index: ksrc/arch/i386/nmi.c
===================================================================
--- ksrc/arch/i386/nmi.c (revision 1316)
+++ ksrc/arch/i386/nmi.c (working copy)
@@ -61,6 +61,9 @@
unsigned long perfctr_msr;
unsigned long long next_linux_check;
unsigned int p4_cccr_val;
+
+ unsigned early_shots;
+ unsigned long long arm_date;
};
char __pad[SMP_CACHE_BYTES];
} rthal_nmi_wd_t ____cacheline_aligned;
@@ -108,8 +111,13 @@
rthal_nmi_wd_t *wd = &rthal_nmi_wds[cpu];
unsigned long long now;
- if (wd->armed)
+ if (wd->armed) {
+ if (rthal_rdtsc() - wd->arm_date < rthal_maxlat_tsc) {
+ ++wd->early_shots;
+ wd->next_linux_check = wd->arm_date + rthal_maxlat_tsc;
+ } else
rthal_nmi_emergency(regs);
+ }
now = rthal_rdtsc();
@@ -142,6 +150,27 @@
wrmsrl(wd->perfctr_msr, now - wd->next_linux_check);
}
+static int earlyshots_read_proc(char *page,
+ char **start,
+ off_t off, int count, int *eof, void *data)
+{
+ int i, len = 0;
+
+ for_each_online_cpu(i)
+ len += sprintf(page + len, "CPU#%d: %u\n",
+ i, rthal_nmi_wds[i].early_shots);
+ len -= off;
+ if (len <= off + count)
+ *eof = 1;
+ *start = page + off;
+ if (len > count)
+ len = count;
+ if (len < 0)
+ len = 0;
+
+ return len;
+}
+
int rthal_nmi_request(void (*emergency) (struct pt_regs *))
{
if (!nmi_active || !nmi_watchdog_tick)
@@ -180,6 +209,11 @@
rthal_linux_nmi_tick = nmi_watchdog_tick;
wmb();
nmi_watchdog_tick = &rthal_nmi_watchdog_tick;
+
+ __rthal_add_proc_leaf("nmi_early_shots",
+ &earlyshots_read_proc,
+ NULL, NULL, rthal_proc_root);
+
return 0;
}
@@ -188,6 +222,8 @@
if (!rthal_linux_nmi_tick)
return;
+ remove_proc_entry("nmi_early_shots", rthal_proc_root);
+
wrmsrl(rthal_nmi_perfctr_msr, 0 - RTHAL_CPU_FREQ);
touch_nmi_watchdog();
wmb();
@@ -215,6 +251,7 @@
rthal_local_irq_restore(flags);
}
+ wd->arm_date = rthal_rdtsc();
wrmsrl(wd->perfctr_msr, 0 - delay);
wmb();
wd->armed = 1;
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