linux-kernel - Re: Regression in 2.6.23-rc2-mm2, mounting cpusets causes a hang

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Message-ID: <20070814192306.GB32553@vino.hallyn.com>
Date:	Tue, 14 Aug 2007 14:23:06 -0500
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Lee Schermerhorn <Lee.Schermerhorn@...com>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>, clameter@....com,
	bob.picco@...com, nacc@...ibm.com, kamezawa.hiroyu@...fujitsu.com,
	mel@...net.ie, akpm@...ux-foundation.org,
	Balbir Singh <balbir@...ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	lkml <linux-kernel@...r.kernel.org>,
	ckrm-tech <ckrm-tech@...ts.sourceforge.net>
Subject: Re: Regression in 2.6.23-rc2-mm2, mounting cpusets causes a hang

Quoting Lee Schermerhorn (Lee.Schermerhorn@...com):
> On Tue, 2007-08-14 at 13:03 -0500, Serge E. Hallyn wrote:
> > Quoting Lee Schermerhorn (Lee.Schermerhorn@...com):
> > > On Mon, 2007-08-13 at 15:12 -0500, Serge E. Hallyn wrote:
> > > > Quoting Dhaval Giani (dhaval@...ux.vnet.ibm.com):
> > > > > Hi,
> > > > > 
> > > > > On mounting cpusets using containers, I have been hitting the following
> > > > > bug.
> > > > > 
> > > > > 
> > > > > -----------[ cut here ]------------
> > > > > kernel BUG at kernel/cpuset.c:331!
> > > <snip>
> > > > > CONFIG_HIGHMEM=y
> > > > > CONFIG_X86_PAE=y
> > > > > # CONFIG_NUMA is not set
> > > > > CONFIG_ARCH_POPULATES_NODE_MAP=y
> > > > > CONFIG_SELECT_MEMORY_MODEL=y
> > > > > CONFIG_FLATMEM_MANUAL=y
> > > > > # CONFIG_DISCONTIGMEM_MANUAL is not set
> > > > > # CONFIG_SPARSEMEM_MANUAL is not set
> > > > > CONFIG_FLATMEM=y
> > > > > CONFIG_FLAT_NODE_MEM_MAP=y
> > > > > # CONFIG_SPARSEMEM_STATIC is not set
> > > > > CONFIG_SPLIT_PTLOCK_CPUS=4
> > > > > CONFIG_RESOURCES_64BIT=y
> > > > > CONFIG_ZONE_DMA_FLAG=1
> > > <snip>
> > > > 
> > > > Yeah, I'm seeing the same thing.  Oddly, my node_states[N_NORMAL_MEMORY]
> > > > and node_states[N_HIGH_MEMORY] are empty, while node_states[N_ONLINE]
> > > > contains my single cpu (on i386 kvm image).
> > > > 
> > > > -serge
> > > 
> > > Yes, you'll definitely hit that BUG if the N_HIGH_MEMORY mask is empty.
> > > So far, I can't see how this could be, tho'.  __build_all_zonelists()
> > > should be called for non-NUMA as well as NUMA.  It iterates over "all
> > 
> > Yup, and it is, and some debug statements insist that
> > node_set_state(nid, N_HIGH_MEMORY) is being called for cpu 0,
> > and the state is in fact being correctly set.
> > 
> > So it must get cleared later...
> 
> OK.  That helps.  I'll see what I can find...

Well apparently I lied?  I don't think it's getting cleared in node_states.
I'm doing:

static void guarantee_online_mems(const struct cpuset *cs, nodemask_t *pmask)
{
        int nid=0;
        printk(KERN_NOTICE "%s: at top, node %d is %d\n",
                __FUNCTION__, nid, node_state(nid, N_HIGH_MEMORY));
        while (cs && !nodes_intersects(cs->mems_allowed,
                                        node_states[N_HIGH_MEMORY])) {
                printk(KERN_NOTICE "%s: in loop\n", __FUNCTION__);
                cs = cs->parent;
        }
        if (cs) {
                printk(KERN_NOTICE "%s: cs was true\n", __FUNCTION__);
                nodes_and(*pmask, cs->mems_allowed,
                                        node_states[N_HIGH_MEMORY]);
        }
        else
        {
                printk(KERN_NOTICE "%s: cs was false\n", __FUNCTION__);
                *pmask = node_states[N_HIGH_MEMORY];
        }
        printk(KERN_NOTICE "%s: at bottom, node %d is %d\n",
                __FUNCTION__, nid, node_state(nid, N_HIGH_MEMORY));
        printk(KERN_NOTICE "%s: at bottom, in pmask node %d is %d\n",
                __FUNCTION__, nid, node_isset(nid, *pmask));
        BUG_ON(!nodes_intersects(*pmask, node_states[N_HIGH_MEMORY]));
}

and getting:

guarantee_online_mems: in loop
guarantee_online_mems: cs was false
guarantee_online_mems: at bottom, node 0 is 1
guarantee_online_mems: at bottom, in pmask node 0 is 0


So I'm guess that
	*pmask = node_states[N_HIGH_MEMORY];
isn't doing what it was intended to do?  That or I've got node_state()
wrong...

-serge
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