Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit f68f447e authored by John Hawkes's avatar John Hawkes Committed by Linus Torvalds
Browse files

[PATCH] ia64 cpuset + build_sched_domains() mangles structures 



I've already sent this to the maintainers, and this is now being sent to a
larger community audience.  I have fixed a problem with the ia64 version of
build_sched_domains(), but a similar fix still needs to be made to the
generic build_sched_domains() in kernel/sched.c.

The "dynamic sched domains" functionality has recently been merged into
2.6.13-rcN that sees the dynamic declaration of a cpu-exclusive (a.k.a.
"isolated") cpuset and rebuilds the CPU Scheduler sched domains and sched
groups to separate away the CPUs in this cpu-exclusive cpuset from the
remainder of the non-isolated CPUs.  This allows the non-isolated CPUs to
completely ignore the isolated CPUs when doing load-balancing.

Unfortunately, build_sched_domains() expects that a sched domain will
include all the CPUs of each node in the domain, i.e., that no node will
belong in both an isolated cpuset and a non-isolated cpuset.  Declaring a
cpuset that violates this presumption will produce flawed data structures
and will oops the kernel.

To trigger the problem (on a NUMA system with >1 CPUs per node):
   cd /dev/cpuset
   mkdir newcpuset
   cd newcpuset
   echo 0 >cpus
   echo 0 >mems
   echo 1 >cpu_exclusive

I have fixed this shortcoming for ia64 NUMA (with multiple CPUs per node).
A similar shortcoming exists in the generic build_sched_domains() (in
kernel/sched.c) for NUMA, and that needs to be fixed also.  The fix
involves dynamically allocating sched_group_nodes[] and
sched_group_allnodes[] for each invocation of build_sched_domains(), rather
than using global arrays for these structures.  Care must be taken to
remember kmalloc() addresses so that arch_destroy_sched_domains() can
properly kfree() the new dynamic structures.

Signed-off-by: default avatarJohn Hawkes <hawkes@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 38f18527

arch/ia64/kernel/domain.c

+69 −21
Original line number Diff line number Diff line
@@ -120,10 +120,10 @@ static int cpu_to_phys_group(int cpu) 
 * gets dynamically allocated.

 */

static DEFINE_PER_CPU(struct sched_domain, node_domains);

static struct sched_group *sched_group_nodes[MAX_NUMNODES];

static struct sched_group **sched_group_nodes_bycpu[NR_CPUS];



static DEFINE_PER_CPU(struct sched_domain, allnodes_domains);

static struct sched_group sched_group_allnodes[MAX_NUMNODES];

static struct sched_group *sched_group_allnodes_bycpu[NR_CPUS];



static int cpu_to_allnodes_group(int cpu)

{
@@ -138,6 +138,21 @@ static int cpu_to_allnodes_group(int cpu) 
void build_sched_domains(const cpumask_t *cpu_map)

{

	int i;

#ifdef CONFIG_NUMA

	struct sched_group **sched_group_nodes = NULL;

	struct sched_group *sched_group_allnodes = NULL;



	/*

	 * Allocate the per-node list of sched groups

	 */

	sched_group_nodes = kmalloc(sizeof(struct sched_group*)*MAX_NUMNODES,

					   GFP_ATOMIC);

	if (!sched_group_nodes) {

		printk(KERN_WARNING "Can not alloc sched group node list\n");

		return;

	}

	sched_group_nodes_bycpu[first_cpu(*cpu_map)] = sched_group_nodes;

#endif



	/*

	 * Set up domains for cpus specified by the cpu_map.
@@ -150,8 +165,21 @@ void build_sched_domains(const cpumask_t *cpu_map) 
		cpus_and(nodemask, nodemask, *cpu_map);



#ifdef CONFIG_NUMA

		if (num_online_cpus()

		if (cpus_weight(*cpu_map)

				> SD_NODES_PER_DOMAIN*cpus_weight(nodemask)) {

			if (!sched_group_allnodes) {

				sched_group_allnodes

					= kmalloc(sizeof(struct sched_group)

							* MAX_NUMNODES,

						  GFP_KERNEL);

				if (!sched_group_allnodes) {

					printk(KERN_WARNING

					"Can not alloc allnodes sched group\n");

					break;

				}

				sched_group_allnodes_bycpu[i]

						= sched_group_allnodes;

			}

			sd = &per_cpu(allnodes_domains, i);

			*sd = SD_ALLNODES_INIT;

			sd->span = *cpu_map;
@@ -214,6 +242,7 @@ void build_sched_domains(const cpumask_t *cpu_map) 
	}



#ifdef CONFIG_NUMA

	if (sched_group_allnodes)

		init_sched_build_groups(sched_group_allnodes, *cpu_map,

					&cpu_to_allnodes_group);
@@ -226,8 +255,10 @@ void build_sched_domains(const cpumask_t *cpu_map) 
		int j;



		cpus_and(nodemask, nodemask, *cpu_map);

		if (cpus_empty(nodemask))

		if (cpus_empty(nodemask)) {

			sched_group_nodes[i] = NULL;

			continue;

		}



		domainspan = sched_domain_node_span(i);

		cpus_and(domainspan, domainspan, *cpu_map);
@@ -372,6 +403,22 @@ void arch_destroy_sched_domains(const cpumask_t *cpu_map) 
{

#ifdef CONFIG_NUMA

	int i;

	int cpu;



	for_each_cpu_mask(cpu, *cpu_map) {

		struct sched_group *sched_group_allnodes

			= sched_group_allnodes_bycpu[cpu];

		struct sched_group **sched_group_nodes

			= sched_group_nodes_bycpu[cpu];



		if (sched_group_allnodes) {

			kfree(sched_group_allnodes);

			sched_group_allnodes_bycpu[cpu] = NULL;

		}



		if (!sched_group_nodes)

			continue;



		for (i = 0; i < MAX_NUMNODES; i++) {

			cpumask_t nodemask = node_to_cpumask(i);

			struct sched_group *oldsg, *sg = sched_group_nodes[i];
@@ -389,8 +436,9 @@ void arch_destroy_sched_domains(const cpumask_t *cpu_map) 
			kfree(oldsg);

			if (oldsg != sched_group_nodes[i])

				goto next_sg;

		sched_group_nodes[i] = NULL;

		}

		kfree(sched_group_nodes);

		sched_group_nodes_bycpu[cpu] = NULL;

	}

#endif

}