[PATCH] nice and rt-prio rlimits

Add a pair of rlimits for allowing non-root tasks to raise nice and rt
priorities. Defaults to traditional behavior. Originally written by
Chris Wright.

The patch implements a simple rlimit ceiling for the RT (and nice) priorities
a task can set.  The rlimit defaults to 0, meaning no change in behavior by
default.  A value of 50 means RT priority levels 1-50 are allowed.  A value of
100 means all 99 privilege levels from 1 to 99 are allowed.  CAP_SYS_NICE is
blanket permission.

(akpm: see http://www.uwsg.iu.edu/hypermail/linux/kernel/0503.1/1921.html for
tips on integrating this with PAM).

Signed-off-by: Matt Mackall <mpm@selenic.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 7 insertions, 1 deletions

diff --git a/include/asm-generic/resource.h b/include/asm-generic/resource.h
index b1fcda9eac23..cfe3692b23e5 100644
--- a/include/asm-generic/resource.h
+++ b/include/asm-generic/resource.h
@@ -41,8 +41,11 @@
 #define RLIMIT_LOCKS            10      /* maximum file locks held */
 #define RLIMIT_SIGPENDING       11      /* max number of pending signals */
 #define RLIMIT_MSGQUEUE         12      /* maximum bytes in POSIX mqueues */
+#define RLIMIT_NICE             13      /* max nice prio allowed to raise to
+                                           0-39 for nice level 19 .. -20 */
+#define RLIMIT_RTPRIO           14      /* maximum realtime priority */
 
-#define RLIM_NLIMITS            13
+#define RLIM_NLIMITS            15
 
 /*
  * SuS says limits have to be unsigned.
@@ -81,6 +84,8 @@
         [RLIMIT_LOCKS]          = {  RLIM_INFINITY,  RLIM_INFINITY },   \
         [RLIMIT_SIGPENDING]     = {             0,             0 },     \
         [RLIMIT_MSGQUEUE]       = {   MQ_BYTES_MAX,   MQ_BYTES_MAX },   \
+        [RLIMIT_NICE]           = { 0, 0 },                             \
+        [RLIMIT_RTPRIO]         = { 0, 0 },                             \
 }
 
 #endif  /* __KERNEL__ */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1cced971232c..8960f99ea128 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -845,6 +845,7 @@ extern void sched_idle_next(void);
 extern void set_user_nice(task_t *p, long nice);
 extern int task_prio(const task_t *p);
 extern int task_nice(const task_t *p);
+extern int can_nice(const task_t *p, const int nice);
 extern int task_curr(const task_t *p);
 extern int idle_cpu(int cpu);
 extern int sched_setscheduler(struct task_struct *, int, struct sched_param *);