[RFC][PATCH 04/11] sched: add resource limits for -deadline tasks.

[Raistlin <raistlin@linux.it>]

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Add resource limits for non-root tasks in using the SCHED_DEADLINE
policy, very similarly to what already exists for RT policies.

In fact, this patch:
 - adds the resource limit RLIMIT_DLDLINE, which is the minimum value
   a user task can use as its own deadline;
 - adds the resource limit RLIMIT_DLRTIME, which is the maximum value
   a user task can use as it own runtime.

Notice that to exploit these, a modified version of the ulimit
utility and a modified resource.h header file are needed. They
both will be available on the website of the project.

Signed-off-by: Dario Faggioli <raistlin@linux.it>
---
 include/asm-generic/resource.h |    7 ++++++-
 kernel/sched.c                 |   25 +++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletions(-)

diff --git a/include/asm-generic/resource.h b/include/asm-generic/resource.h
index 587566f..4a1d0e2 100644
--- a/include/asm-generic/resource.h
+++ b/include/asm-generic/resource.h
@@ -45,7 +45,10 @@
 					   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_DLDLINE		16	/* minimum deadline in us */
+#define RLIMIT_DLRTIME		17	/* maximum runtime in us */
+#define RLIM_NLIMITS		18
 
 /*
  * SuS says limits have to be unsigned.
@@ -87,6 +90,8 @@
 	[RLIMIT_NICE]		= { 0, 0 },				\
 	[RLIMIT_RTPRIO]		= { 0, 0 },				\
 	[RLIMIT_RTTIME]		= {  RLIM_INFINITY,  RLIM_INFINITY },	\
+	[RLIMIT_DLDLINE]	= { ULONG_MAX, ULONG_MAX },		\
+	[RLIMIT_DLRTIME]	= { 0, 0 },				\
 }
 
 #endif	/* __KERNEL__ */
diff --git a/kernel/sched.c b/kernel/sched.c
index 19e90fc..61b1561 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6407,6 +6407,31 @@ recheck:
 	 * Allow unprivileged RT tasks to decrease priority:
 	 */
 	if (user && !capable(CAP_SYS_NICE)) {
+		if (dl_policy(policy)) {
+			u64 rlim_dline, rlim_rtime;
+			u64 dline, rtime;
+
+			if (!lock_task_sighand(p, &flags))
+				return -ESRCH;
+			rlim_dline = p->signal->rlim[RLIMIT_DLDLINE].rlim_cur;
+			rlim_rtime = p->signal->rlim[RLIMIT_DLRTIME].rlim_cur;
+			unlock_task_sighand(p, &flags);
+
+			/* can't set/change -deadline policy */
+			if (policy != p->policy && !rlim_rtime)
+				return -EPERM;
+
+			/* can't decrease the deadline */
+			rlim_dline *= NSEC_PER_USEC;
+			dline = timespec_to_ns(&param_ex->sched_deadline);
+			if (dline < p->dl.dl_deadline && dline < rlim_dline)
+				return -EPERM;
+			/* can't increase the runtime */
+			rlim_rtime *= NSEC_PER_USEC;
+			rtime = timespec_to_ns(&param_ex->sched_runtime);
+			if (rtime > p->dl.dl_runtime && rtime > rlim_rtime)
+				return -EPERM;
+		}
 		if (rt_policy(policy)) {
 			unsigned long rlim_rtprio;
 
-- 
1.7.0

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
----------------------------------------------------------------------
Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa  (Italy)

http://blog.linux.it/raistlin / raistlin@ekiga.net /
dario.faggioli@jabber.org

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