[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: John 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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 69 insertions, 21 deletions

diff --git a/arch/ia64/kernel/domain.c b/arch/ia64/kernel/domain.c
index bbb8efe126b..e907109983f 100644
--- a/arch/ia64/kernel/domain.c
+++ b/arch/ia64/kernel/domain.c
@@ -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;
@@ -214,8 +242,9 @@ void build_sched_domains(const cpumask_t *cpu_map)
         }
 
 #ifdef CONFIG_NUMA
-        init_sched_build_groups(sched_group_allnodes, *cpu_map,
-                                &cpu_to_allnodes_group);
+        if (sched_group_allnodes)
+                init_sched_build_groups(sched_group_allnodes, *cpu_map,
+                                        &cpu_to_allnodes_group);
 
         for (i = 0; i < MAX_NUMNODES; i++) {
                 /* Set up node groups */
@@ -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);
@@ -372,25 +403,42 @@ void arch_destroy_sched_domains(const cpumask_t *cpu_map)
 {
 #ifdef CONFIG_NUMA
         int i;
-        for (i = 0; i < MAX_NUMNODES; i++) {
-                cpumask_t nodemask = node_to_cpumask(i);
-                struct sched_group *oldsg, *sg = sched_group_nodes[i];
+        int cpu;
 
-                cpus_and(nodemask, nodemask, *cpu_map);
-                if (cpus_empty(nodemask))
-                        continue;
+        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 (sg == NULL)
+                if (sched_group_allnodes) {
+                        kfree(sched_group_allnodes);
+                        sched_group_allnodes_bycpu[cpu] = NULL;
+                }
+
+                if (!sched_group_nodes)
                         continue;
-                sg = sg->next;
+
+                for (i = 0; i < MAX_NUMNODES; i++) {
+                        cpumask_t nodemask = node_to_cpumask(i);
+                        struct sched_group *oldsg, *sg = sched_group_nodes[i];
+
+                        cpus_and(nodemask, nodemask, *cpu_map);
+                        if (cpus_empty(nodemask))
+                                continue;
+
+                        if (sg == NULL)
+                                continue;
+                        sg = sg->next;
 next_sg:
-                oldsg = sg;
-                sg = sg->next;
-                kfree(oldsg);
-                if (oldsg != sched_group_nodes[i])
-                        goto next_sg;
-                sched_group_nodes[i] = NULL;
+                        oldsg = sg;
+                        sg = sg->next;
+                        kfree(oldsg);
+                        if (oldsg != sched_group_nodes[i])
+                                goto next_sg;
+                }
+                kfree(sched_group_nodes);
+                sched_group_nodes_bycpu[cpu] = NULL;
         }
 #endif
 }
-