lkml.org 
[lkml]   [2006]   [Mar]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH 2.6.16-mm1 1/2] sched_domain: handle kmalloc failure
    I think there is a bug in build_sched_domains() when kmalloc fails to
    allocate memory for 'sched_group_allnodes'.

    Consider the case where build_sched_domains() is being invoked because a
    CPUset is being made exclusive. Further lets say user changed cpu_exclusive
    property of some CPUset as follow:

    echo 1 > cpu_exclusive # (Step a)
    echo 0 > cpu_exclusive # (Step b)
    echo 1 > cpu_exclusive # (Step c)


    Lets say that all memory allocations succeeded during the 1st attempt to
    make CPUset exclusive (Step a). Step a would result in the sched domain
    heirarchy being initialized for all CPUs in the CPUSet under
    consideration. Step b would cause those memory allocations to be freed
    up.

    Now during Step c, lets say that kmalloc failed to allocate for
    'sched_group_allnodes'. When that happens, the code just breaks out of
    the 'for' loop. I think that is wrong, as it would cause the previous
    assignments (made during Step a) to be retained. This could cause, among
    other things, sd->groups to be invalid (for allnodes_domains)?

    Patch below (against 2.6.16-mm1) fixes it. I have done some minimal test
    of it.

    Signed-off-by: Srivatsa Vaddagiri <vatsa@in.ibm.com>



    kernel/sched.c | 10 +++++++---
    1 files changed, 7 insertions(+), 3 deletions(-)

    diff -puN kernel/sched.c~sd_handle_error kernel/sched.c
    --- linux-2.6.16-mm1/kernel/sched.c~sd_handle_error 2006-03-25 11:39:07.000000000 +0530
    +++ linux-2.6.16-mm1-root/kernel/sched.c 2006-03-25 11:39:59.000000000 +0530
    @@ -5965,6 +5965,7 @@ void build_sched_domains(const cpumask_t
    {
    int i;
    #ifdef CONFIG_NUMA
    + int alloc_failed = 0;
    struct sched_group **sched_group_nodes = NULL;
    struct sched_group *sched_group_allnodes = NULL;

    @@ -5993,7 +5994,7 @@ void build_sched_domains(const cpumask_t
    #ifdef CONFIG_NUMA
    if (cpus_weight(*cpu_map)
    > SD_NODES_PER_DOMAIN*cpus_weight(nodemask)) {
    - if (!sched_group_allnodes) {
    + if (!sched_group_allnodes && !alloc_failed) {
    sched_group_allnodes
    = kmalloc(sizeof(struct sched_group)
    * MAX_NUMNODES,
    @@ -6001,7 +6002,7 @@ void build_sched_domains(const cpumask_t
    if (!sched_group_allnodes) {
    printk(KERN_WARNING
    "Can not alloc allnodes sched group\n");
    - break;
    + alloc_failed = 1;
    }
    sched_group_allnodes_bycpu[i]
    = sched_group_allnodes;
    @@ -6010,7 +6011,10 @@ void build_sched_domains(const cpumask_t
    *sd = SD_ALLNODES_INIT;
    sd->span = *cpu_map;
    group = cpu_to_allnodes_group(i);
    - sd->groups = &sched_group_allnodes[group];
    + sd->groups = sched_group_allnodes ?
    + &sched_group_allnodes[group] : NULL;
    + if (!sd->groups)
    + sd->flags = 0; /* No load balancing */
    p = sd;
    } else
    p = NULL;
    _

    --
    Regards,
    vatsa
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2006-03-25 09:30    [W:0.022 / U:9.028 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site