Messages in this thread Patch in this message | | | Date | Wed, 10 Nov 2010 20:35:41 -0800 | From | Mandeep Singh Baines <> | Subject | [PATCH] oom: create a resource limit for oom_adj |
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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
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