lkml.org 
[lkml]   [2014]   [Feb]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 48/51] mm, vmstat: Fix CPU hotplug callback registration
    Date
    Subsystems that want to register CPU hotplug callbacks, as well as perform
    initialization for the CPUs that are already online, often do it as shown
    below:

    get_online_cpus();

    for_each_online_cpu(cpu)
    init_cpu(cpu);

    register_cpu_notifier(&foobar_cpu_notifier);

    put_online_cpus();

    This is wrong, since it is prone to ABBA deadlocks involving the
    cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
    with CPU hotplug operations).

    Instead, the correct and race-free way of performing the callback
    registration is:

    cpu_maps_update_begin();

    for_each_online_cpu(cpu)
    init_cpu(cpu);

    /* Note the use of the double underscored version of the API */
    __register_cpu_notifier(&foobar_cpu_notifier);

    cpu_maps_update_done();


    Fix the vmstat code in the MM subsystem by using this latter form of callback
    registration.

    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Christoph Lameter <cl@linux.com>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
    Cc: Cody P Schafer <cody@linux.vnet.ibm.com>
    Cc: Toshi Kani <toshi.kani@hp.com>
    Cc: Dave Hansen <dave@sr71.net>
    Cc: linux-mm@kvack.org
    Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    ---

    mm/vmstat.c | 6 +++---
    1 file changed, 3 insertions(+), 3 deletions(-)

    diff --git a/mm/vmstat.c b/mm/vmstat.c
    index 7249614..70668ba 100644
    --- a/mm/vmstat.c
    +++ b/mm/vmstat.c
    @@ -1290,14 +1290,14 @@ static int __init setup_vmstat(void)
    #ifdef CONFIG_SMP
    int cpu;

    - register_cpu_notifier(&vmstat_notifier);
    + cpu_maps_update_begin();
    + __register_cpu_notifier(&vmstat_notifier);

    - get_online_cpus();
    for_each_online_cpu(cpu) {
    start_cpu_timer(cpu);
    node_set_state(cpu_to_node(cpu), N_CPU);
    }
    - put_online_cpus();
    + cpu_maps_update_done();
    #endif
    #ifdef CONFIG_PROC_FS
    proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations);


    \
     
     \ /
      Last update: 2014-02-06 04:01    [W:4.131 / U:0.908 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site