[PATCH] sched_domai: Allocate sched_group structures dynamically

As explained here:
	http://marc.theaimsgroup.com/?l=linux-kernel&m=114327539012323&w=2

there is a problem with sharing sched_group structures between two
separate sched_group structures for different sched_domains.

The patch has been tested and found to avoid the kernel lockup problem
described in above URL.

Signed-off-by: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 43 insertions, 5 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index ee4211bd40c5..122b75584a13 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5747,7 +5747,7 @@ static int cpu_to_cpu_group(int cpu)
 
 #ifdef CONFIG_SCHED_MC
 static DEFINE_PER_CPU(struct sched_domain, core_domains);
-static struct sched_group sched_group_core[NR_CPUS];
+static struct sched_group *sched_group_core_bycpu[NR_CPUS];
 #endif
 
 #if defined(CONFIG_SCHED_MC) && defined(CONFIG_SCHED_SMT)
@@ -5763,7 +5763,7 @@ static int cpu_to_core_group(int cpu)
 #endif
 
 static DEFINE_PER_CPU(struct sched_domain, phys_domains);
-static struct sched_group sched_group_phys[NR_CPUS];
+static struct sched_group *sched_group_phys_bycpu[NR_CPUS];
 static int cpu_to_phys_group(int cpu)
 {
 #if defined(CONFIG_SCHED_MC)
@@ -5823,9 +5823,9 @@ next_sg:
 /* Free memory allocated for various sched_group structures */
 static void free_sched_groups(const cpumask_t *cpu_map)
 {
+        int cpu;
 #ifdef CONFIG_NUMA
         int i;
-        int cpu;
 
         for_each_cpu_mask(cpu, *cpu_map) {
                 struct sched_group *sched_group_allnodes
@@ -5863,6 +5863,18 @@ next_sg:
                 sched_group_nodes_bycpu[cpu] = NULL;
         }
 #endif
+        for_each_cpu_mask(cpu, *cpu_map) {
+                if (sched_group_phys_bycpu[cpu]) {
+                        kfree(sched_group_phys_bycpu[cpu]);
+                        sched_group_phys_bycpu[cpu] = NULL;
+                }
+#ifdef CONFIG_SCHED_MC
+                if (sched_group_core_bycpu[cpu]) {
+                        kfree(sched_group_core_bycpu[cpu]);
+                        sched_group_core_bycpu[cpu] = NULL;
+                }
+#endif
+        }
 }
 
 /*
@@ -5872,6 +5884,10 @@ next_sg:
 static int build_sched_domains(const cpumask_t *cpu_map)
 {
         int i;
+        struct sched_group *sched_group_phys = NULL;
+#ifdef CONFIG_SCHED_MC
+        struct sched_group *sched_group_core = NULL;
+#endif
 #ifdef CONFIG_NUMA
         struct sched_group **sched_group_nodes = NULL;
         struct sched_group *sched_group_allnodes = NULL;
@@ -5930,6 +5946,18 @@ static int build_sched_domains(const cpumask_t *cpu_map)
                 cpus_and(sd->span, sd->span, *cpu_map);
 #endif
 
+                if (!sched_group_phys) {
+                        sched_group_phys
+                                = kmalloc(sizeof(struct sched_group) * NR_CPUS,
+                                          GFP_KERNEL);
+                        if (!sched_group_phys) {
+                                printk (KERN_WARNING "Can not alloc phys sched"
+                                                     "group\n");
+                                goto error;
+                        }
+                        sched_group_phys_bycpu[i] = sched_group_phys;
+                }
+
                 p = sd;
                 sd = &per_cpu(phys_domains, i);
                 group = cpu_to_phys_group(i);
@@ -5939,6 +5967,18 @@ static int build_sched_domains(const cpumask_t *cpu_map)
                 sd->groups = &sched_group_phys[group];
 
 #ifdef CONFIG_SCHED_MC
+                if (!sched_group_core) {
+                        sched_group_core
+                                = kmalloc(sizeof(struct sched_group) * NR_CPUS,
+                                          GFP_KERNEL);
+                        if (!sched_group_core) {
+                                printk (KERN_WARNING "Can not alloc core sched"
+                                                     "group\n");
+                                goto error;
+                        }
+                        sched_group_core_bycpu[i] = sched_group_core;
+                }
+
                 p = sd;
                 sd = &per_cpu(core_domains, i);
                 group = cpu_to_core_group(i);
@@ -6134,11 +6174,9 @@ static int build_sched_domains(const cpumask_t *cpu_map)
 
         return 0;
 
-#ifdef CONFIG_NUMA
 error:
         free_sched_groups(cpu_map);
         return -ENOMEM;
-#endif
 }
 /*
  * Set up scheduler domains and groups.  Callers must hold the hotplug lock.