linux-kernel - Re: [Bug #11342] Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c

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Date:	Mon, 25 Aug 2008 13:52:23 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"Alan D. Brunelle" <Alan.Brunelle@...com>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [Bug #11342] Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c -
 bisected



On Mon, 25 Aug 2008, Linus Torvalds wrote:
> 
> But I'll look at your vmlinux, see what stands out.

Oops. I already see the problem.

Your .config has soem _huge_ CPU count, doesn't it?

checkstack.pl shows these things as the top problems:

	0xffffffff80266234 smp_call_function_mask [vmlinux]:    2736
	0xffffffff80234747 __build_sched_domains [vmlinux]:     2232
	0xffffffff8023523f __build_sched_domains [vmlinux]:     2232
	0xffffffff8021e884 setup_IO_APIC_irq [vmlinux]:         1616
	0xffffffff8021ee24 arch_setup_ht_irq [vmlinux]:         1600
	0xffffffff8021f144 arch_setup_msi_irq [vmlinux]:        1600
	0xffffffff8021e3b0 __assign_irq_vector [vmlinux]:       1592
	0xffffffff8021e626 __assign_irq_vector [vmlinux]:       1592
	0xffffffff8023257e move_task_off_dead_cpu [vmlinux]:    1592
	0xffffffff802326e8 move_task_off_dead_cpu [vmlinux]:    1592
	0xffffffff8025dbc5 tick_handle_oneshot_broadcast [vmlinux]:1544
	0xffffffff8025dcb4 tick_handle_oneshot_broadcast [vmlinux]:1544
	0xffffffff803f3dc4 store_scaling_governor [vmlinux]:    1376
	0xffffffff80279ef4 cpuset_write_resmask [vmlinux]:      1360
	0xffffffff803f465d cpufreq_add_dev [vmlinux]:           1352
	0xffffffff803f495b cpufreq_add_dev [vmlinux]:           1352
	0xffffffff803f3fc4 store_scaling_max_freq [vmlinux]:    1328
	0xffffffff803f4064 store_scaling_min_freq [vmlinux]:    1328
	0xffffffff803f44c4 cpufreq_update_policy [vmlinux]:     1328
	..

and sys_init_module is actually way way down the list. I bet the only 
reason it showed up at all was because dynamically it was such a deep 
callchain, and part of that callchain probably called some of those really 
nasty things.

Anyway, the reason smp_call_function_mask and friends have such _huge_ 
stack usages for you is that they contain a 'cpumask_t' on the stack.

For example, for me, usign a sane NR_CPU, the size of the stack frame for 
smp_call_function_mask is under 200 bytes.  For you, it's 2736 bytes.

How about you make CONFIG_NR_CPU's something _sane_? Like 16? Or do you 
really have four thousand CPU's in that system?

Oh, I guess you have the MAXSMP config enabled? I really think that was a 
bit too aggressive.

		Linus
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