lkml.org 
[lkml]   [2010]   [Nov]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH] oom: create a resource limit for oom_adj
    For ChromiumOS, we'd like to be able to oom_adj a process up/down
    as its leaves/enters the foreground. Currently, it is not possible
    to oom_adj down without CAP_SYS_RESOURCE. This patch creates a new
    resource limit, RLIMIT_OOMADJ, which is works in a similar fashion
    to RLIMIT_NICE. This allows a process's oom_adj to be lowered
    without CAP_SYS_RESOURCE as long as the new value is greater
    than the resource limit.

    Alternative considered:

    * a setuid binary
    * a daemon with CAP_SYS_RESOURCE

    Since you don't wan't all processes to be able to reduce their
    oom_adj, a setuid or daemon implementation would be complex. The
    alternatives also have much higher overhead.

    Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
    ---
    fs/proc/base.c | 12 ++++++++++--
    include/asm-generic/resource.h | 5 ++++-
    2 files changed, 14 insertions(+), 3 deletions(-)

    diff --git a/fs/proc/base.c b/fs/proc/base.c
    index f3d02ca..4384013 100644
    --- a/fs/proc/base.c
    +++ b/fs/proc/base.c
    @@ -462,6 +462,7 @@ static const struct limit_names lnames[RLIM_NLIMITS] = {
    [RLIMIT_NICE] = {"Max nice priority", NULL},
    [RLIMIT_RTPRIO] = {"Max realtime priority", NULL},
    [RLIMIT_RTTIME] = {"Max realtime timeout", "us"},
    + [RLIMIT_OOMADJ] = {"Max OOM adjust", NULL},
    };

    /* Display limits for a process */
    @@ -1057,8 +1058,15 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
    }

    if (oom_adjust < task->signal->oom_adj && !capable(CAP_SYS_RESOURCE)) {
    - err = -EACCES;
    - goto err_sighand;
    + /* convert oom_adj [15,-17] to rlimit style value [1,33] */
    + long oom_rlim = OOM_ADJUST_MAX + 1 - oom_adjust;
    +
    + if (oom_rlim > task->signal->rlim[RLIMIT_OOMADJ].rlim_cur) {
    + unlock_task_sighand(task, &flags);
    + put_task_struct(task);
    + err = -EACCES;
    + goto err_sighand;
    + }
    }

    if (oom_adjust != task->signal->oom_adj) {
    diff --git a/include/asm-generic/resource.h b/include/asm-generic/resource.h
    index 587566f..a8640a4 100644
    --- a/include/asm-generic/resource.h
    +++ b/include/asm-generic/resource.h
    @@ -45,7 +45,9 @@
    0-39 for nice level 19 .. -20 */
    #define RLIMIT_RTPRIO 14 /* maximum realtime priority */
    #define RLIMIT_RTTIME 15 /* timeout for RT tasks in us */
    -#define RLIM_NLIMITS 16
    +#define RLIMIT_OOMADJ 16 /* max oom_adj allowed to lower to
    + 0-32 for oom level 15 .. -17 */
    +#define RLIM_NLIMITS 17

    /*
    * SuS says limits have to be unsigned.
    @@ -86,6 +88,7 @@
    [RLIMIT_MSGQUEUE] = { MQ_BYTES_MAX, MQ_BYTES_MAX }, \
    [RLIMIT_NICE] = { 0, 0 }, \
    [RLIMIT_RTPRIO] = { 0, 0 }, \
    + [RLIMIT_OOMADJ] = { 0, 0 }, \
    [RLIMIT_RTTIME] = { RLIM_INFINITY, RLIM_INFINITY }, \
    }

    --
    1.7.3.1


    \
     
     \ /
      Last update: 2010-11-11 05:39    [W:0.023 / U:0.436 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site