On Tue, 2007-08-28 at 12:46 -0700, Stephane Eranian wrote:
> I think I found the problem. As I suspected, it seems there is an assymetry > between the 1st end 2nd counter (just like what they have on P6 core). Yet > for architectural perfmon v1, this restriction is supposed to be lifted. > > Unfortunately, a quick look at the errata document at > http://download.intel.com/design/mobile/SPECUPDT/30922212.pdf > > for Core Duo shows bugs A49 as 'nofix': > Core Duo processor has a bug which renders the enable bit (22) of > PERFEVTSEL1 inoperative. The processor behaves like former P6 cores, > the enable bit of PERFEVTSEL0 controls the activation of both counters Your patch switched the nmi from PERFEVTSEL0 to PERFEVTSEL1 (right?).. So 0 works, 1 does not , for me anyway .. > That explains why you get the 'NMI stuck' message when using PERFEVTSEL1. > I suspect when using PERFEVTSEL0, then NMI watchdog is not stuck. So it > is possible that in case NMI is stuck the code does not cleanly shutdown the > NMI interrupt and you get some spurious NMI interrupt later in the boot at > you are stuck because you are holding a lock. We need to look at the error > path of check_nmi_watchdog(). I glance through it and could not find the place > where the APIC vector is cleared. As far as I can tell the check_nmi_watchdog() doesn't take locks, and it can't safely share a lock with the NMI .. The patch below fixes the hang (not the stuck NMI) .. Not totally sure why, but the cpus are stuck in a loop waiting for the endflag which never comes .. This also plays with the nmi hz which might do something.. /proc/interrupt doesn't show any nmi's either.. Daniel Signed-off-by: Daniel Walker <[EMAIL PROTECTED]> Index: linux-2.6.22/arch/i386/kernel/nmi.c =================================================================== --- linux-2.6.22.orig/arch/i386/kernel/nmi.c 2007-08-15 00:51:12.000000000 +0000 +++ linux-2.6.22/arch/i386/kernel/nmi.c 2007-08-28 20:15:04.000000000 +0000 @@ -82,7 +82,7 @@ static __init void nmi_cpu_busy(void *da static int __init check_nmi_watchdog(void) { unsigned int *prev_nmi_count; - int cpu; + int cpu, ret = 0; if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DEFAULT)) return 0; @@ -125,18 +125,18 @@ static int __init check_nmi_watchdog(voi if (!atomic_read(&nmi_active)) { kfree(prev_nmi_count); atomic_set(&nmi_active, -1); - return -1; - } + printk("nmi malfunctioning.\n"); + ret = -1; + } else + printk("OK.\n"); endflag = 1; - printk("OK.\n"); - /* now that we know it works we can reduce NMI frequency to something more reasonable; makes a difference in some configs */ if (nmi_watchdog == NMI_LOCAL_APIC) nmi_hz = lapic_adjust_nmi_hz(1); kfree(prev_nmi_count); - return 0; + return ret; } /* This needs to happen later in boot so counters are working */ late_initcall(check_nmi_watchdog); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
