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SubjectRe: [PATCH] disable softlockup detection at boottime
On Mon, Apr 28, 2008 at 06:55:44PM +0200, Ingo Molnar wrote:
>
> good idea - but why dont you set softlockup_thresh to 0, which is the
> "off" switch already? (and that way it can be turned back on later as
> well, by the sysadmin.)
>

I'm getting unaligned access errors trying to set it to anything, so it's not working for me currently (2.6.25):

It's tripping up on the address of 'one', which is an int that is not properly aligned for the unsigned long comparison in proc_doulongvec_minmax on my 64 bit machine. Also, the value '0' is invalid for softlockup_thresh, correct?

I temporarily got around these issues with the following hack.

Index: linux/kernel/sysctl.c
===================================================================
--- linux.orig/kernel/sysctl.c 2008-04-16 21:49:44.000000000 -0500
+++ linux/kernel/sysctl.c 2008-04-28 13:37:43.000561710 -0500
@@ -748,9 +748,9 @@ static struct ctl_table kern_table[] = {
.data = &softlockup_thresh,
.maxlen = sizeof(unsigned long),
.mode = 0644,
- .proc_handler = &proc_doulongvec_minmax,
+ .proc_handler = &proc_dointvec_minmax,
.strategy = &sysctl_intvec,
- .extra1 = &one,
+ .extra1 = &zero,
.extra2 = &sixty,


Also, I'm not convinced that changing this to 0 does indeed switch off softlockup detection (but I could be missing something):

void softlockup_tick(void)
{
..
..
/* Warn about unreasonable delays: */
if (now <= (touch_timestamp + softlockup_thresh))
return;
per_cpu(print_timestamp, this_cpu) = touch_timestamp;

spin_lock(&print_lock);
printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n",
this_cpu, now - touch_timestamp,
current->comm, task_pid_nr(current));


Dimitri


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