Messages in this thread | ![/](/images/icornerl.gif) | | Date | Sat, 13 Nov 2010 17:37:35 -0800 (PST) | From | David Rientjes <> | Subject | Re: [PATCH] oom: allow a non-CAP_SYS_RESOURCE proces to oom_score_adj down |
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On Fri, 12 Nov 2010, Mandeep Singh Baines wrote:
> We'd like to be able to oom_score_adj a process up/down as its > enters/leaves the foreground. Currently, it is not possible to oom_adj > down without CAP_SYS_RESOURCE. This patch allows a task to decrease > its oom_score_adj back to the value that a CAP_SYS_RESOURCE thread set > it or its inherited value at fork. Assuming the thread that has forked > it has oom_score_adj of 0, each tab could decrease it back from 0 upon > activation unless a CAP_SYS_RESOURCE thread elevated it to something > higher. >
oom_score_adj_min doesn't appear to be inherited at fork in your patch.
> 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. >
This behavior should be documented in Documentation/filesystems/proc.txt.
> This patch updated based on feedback from > David Rientjes <rientjes@google.com>. > > Change-Id: If8f52363fd6c156e1730f43148aee987260e9c72
I know what a Change-Id is , but nobody else here does :)
> Signed-off-by: Mandeep Singh Baines <msb@chromium.org> > --- > fs/proc/base.c | 4 +++- > include/linux/sched.h | 2 ++ > 2 files changed, 5 insertions(+), 1 deletions(-) > > diff --git a/fs/proc/base.c b/fs/proc/base.c > index f3d02ca..e617413 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -1164,7 +1164,7 @@ static ssize_t oom_score_adj_write(struct file *file, const char __user *buf, > goto err_task_lock; > } > > - if (oom_score_adj < task->signal->oom_score_adj && > + if (oom_score_adj < task->signal->oom_score_adj_min && > !capable(CAP_SYS_RESOURCE)) { > err = -EACCES; > goto err_sighand; > @@ -1177,6 +1177,8 @@ static ssize_t oom_score_adj_write(struct file *file, const char __user *buf, > atomic_dec(&task->mm->oom_disable_count); > } > task->signal->oom_score_adj = oom_score_adj; > + if (capable(CAP_SYS_RESOURCE)) > + task->signal->oom_score_adj_min = oom_score_adj; > /* > * Scale /proc/pid/oom_adj appropriately ensuring that OOM_DISABLE is > * always attainable. > diff --git a/include/linux/sched.h b/include/linux/sched.h > index f53cdf2..2a71ee0 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -626,6 +626,8 @@ struct signal_struct { > > int oom_adj; /* OOM kill score adjustment (bit shift) */ > int oom_score_adj; /* OOM kill score adjustment */ > + int oom_score_adj_min; /* OOM kill score adjustment minimum value. > + * Only settable by CAP_SYS_RESOURCE. */ > > struct mutex cred_guard_mutex; /* guard against foreign influences on > * credential calculations
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