Commit:     7378547f2c83ca16a30d0a7c488a43a688ea0888
Parent:     c9927c2bf4f45bb85e8b502ab3fb79ad6483c244
Author:     Milton Miller <[EMAIL PROTECTED]>
AuthorDate: Wed Oct 24 18:23:48 2007 +0200
Committer:  Ingo Molnar <[EMAIL PROTECTED]>
CommitDate: Wed Oct 24 18:23:48 2007 +0200

    sched: fix sched_domain sysctl registration again
    commit  029190c515f15f512ac85de8fc686d4dbd0ae731 (cpuset
    sched_load_balance flag) was not tested SCHED_DEBUG enabled as
    committed as it dereferences NULL when used and it reordered
    the sysctl registration to cause it to never show any domains
    or their tunables.
    1) restore arch_init_sched_domains ordering
        we can't walk the domains before we build them
        presently we register cpus with empty directories (no domain
        directories or files).
    2) make unregister_sched_domain_sysctl do nothing when already unregistered
        detach_destroy_domains is now called one set of cpus at a time
        unregister_syctl dereferences NULL if called with a null.
        While the the function would always dereference null if called
        twice, in the previous code it was always called once and then
        was followed a register.  So only the hidden bug of the
        sysctl_root_table not being allocated followed by an attempt to
        free it would have shown the error.
    3) always call unregister and register in partition_sched_domains
        The code is "smart" about unregistering only needed domains.
        Since we aren't guaranteed any calls to unregister, always
        unregister.   Without calling register on the way out we
        will not have a table or any sysctl tree.
    4) warn if register is called without unregistering
        The previous table memory is lost, leaving pointers to the
        later freed memory in sysctl and leaking the memory of the
    Before this patch on a 2-core 4-thread box compiled for SMT and NUMA,
    the domains appear empty (there are actually 3 levels per cpu).  And as
    soon as two domains a null pointer is dereferenced (unreliable in this
    case is stack garbage):
    bu19a:~# ls -R /proc/sys/kernel/sched_domain/
    cpu0  cpu1  cpu2  cpu3
    bu19a:~# mkdir /dev/cpuset
    bu19a:~# mount -tcpuset cpuset /dev/cpuset/
    bu19a:~# cd /dev/cpuset/
    bu19a:/dev/cpuset# echo 0 > sched_load_balance
    bu19a:/dev/cpuset# mkdir one
    bu19a:/dev/cpuset# echo 1 > one/cpus
    bu19a:/dev/cpuset# echo 0 > one/sched_load_balance
    Unable to handle kernel paging request for data at address 0x00000018
    Faulting instruction address: 0xc00000000006b608
    NIP: c00000000006b608 LR: c00000000006b604 CTR: 0000000000000000
    REGS: c000000018d973f0 TRAP: 0300   Not tainted  (2.6.23-bml)
    MSR: 9000000000009032 <EE,ME,IR,DR>  CR: 28242442  XER: 00000000
    DAR: 0000000000000018, DSISR: 0000000040000000
    TASK = c00000001912e340[1987] 'bash' THREAD: c000000018d94000 CPU: 2
    NIP [c00000000006b608] .unregister_sysctl_table+0x38/0x110
    LR [c00000000006b604] .unregister_sysctl_table+0x34/0x110
    Call Trace:
    [c000000018d97670] [c000000007017270] 0xc000000007017270 (unreliable)
    [c000000018d97720] [c000000000058710] .detach_destroy_domains+0x30/0xb0
    [c000000018d977b0] [c00000000005cf1c] .partition_sched_domains+0x1bc/0x230
    [c000000018d97870] [c00000000009fdc4] .rebuild_sched_domains+0xb4/0x4c0
    [c000000018d97970] [c0000000000a02e8] .update_flag+0x118/0x170
    [c000000018d97a80] [c0000000000a1768] .cpuset_common_file_write+0x568/0x820
    [c000000018d97c00] [c00000000009d95c] .cgroup_file_write+0x7c/0x180
    [c000000018d97cf0] [c0000000000e76b8] .vfs_write+0xe8/0x1b0
    [c000000018d97d90] [c0000000000e810c] .sys_write+0x4c/0x90
    [c000000018d97e30] [c00000000000852c] syscall_exit+0x0/0x40
    Signed-off-by: Milton Miller <[EMAIL PROTECTED]>
    Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
 kernel/sched.c |   25 ++++++++++++++++++++-----
 1 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 2810e56..e51f0ea 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5461,11 +5461,12 @@ static void register_sched_domain_sysctl(void)
        struct ctl_table *entry = sd_alloc_ctl_entry(cpu_num + 1);
        char buf[32];
+       WARN_ON(sd_ctl_dir[0].child);
+       sd_ctl_dir[0].child = entry;
        if (entry == NULL)
-       sd_ctl_dir[0].child = entry;
        for_each_online_cpu(i) {
                snprintf(buf, 32, "cpu%d", i);
                entry->procname = kstrdup(buf, GFP_KERNEL);
@@ -5473,14 +5474,19 @@ static void register_sched_domain_sysctl(void)
                entry->child = sd_alloc_ctl_cpu_table(i);
+       WARN_ON(sd_sysctl_header);
        sd_sysctl_header = register_sysctl_table(sd_ctl_root);
+/* may be called multiple times per register */
 static void unregister_sched_domain_sysctl(void)
-       unregister_sysctl_table(sd_sysctl_header);
+       if (sd_sysctl_header)
+               unregister_sysctl_table(sd_sysctl_header);
        sd_sysctl_header = NULL;
-       sd_free_ctl_entry(&sd_ctl_dir[0].child);
+       if (sd_ctl_dir[0].child)
+               sd_free_ctl_entry(&sd_ctl_dir[0].child);
 static void register_sched_domain_sysctl(void)
@@ -6424,13 +6430,17 @@ static cpumask_t fallback_doms;
 static int arch_init_sched_domains(const cpumask_t *cpu_map)
+       int err;
        ndoms_cur = 1;
        doms_cur = kmalloc(sizeof(cpumask_t), GFP_KERNEL);
        if (!doms_cur)
                doms_cur = &fallback_doms;
        cpus_andnot(*doms_cur, *cpu_map, cpu_isolated_map);
+       err = build_sched_domains(doms_cur);
-       return build_sched_domains(doms_cur);
+       return err;
 static void arch_destroy_sched_domains(const cpumask_t *cpu_map)
@@ -6479,6 +6489,9 @@ void partition_sched_domains(int ndoms_new, cpumask_t 
        int i, j;
+       /* always unregister in case we don't destroy any domains */
+       unregister_sched_domain_sysctl();
        if (doms_new == NULL) {
                ndoms_new = 1;
                doms_new = &fallback_doms;
@@ -6514,6 +6527,8 @@ match2:
        doms_cur = doms_new;
        ndoms_cur = ndoms_new;
+       register_sched_domain_sysctl();
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
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