>From 25aa166505aff2561dd715c927c654d0bbb432ba Mon Sep 17 00:00:00 2001
From: raz <raziebe@xxxxxxxxx>
Date: Tue, 20 Dec 2011 22:54:56 +0200
Add positioning routine find_pos. find_pos returns
the place where to put the sleeper before.
I sort only rt tasks, OTHER policy is pushed back in
queue. I do not distinct between SCHED_RR and SCHED_FIFO
policies and they are treated as a single policy
for the sorting algorithm.
SETPRIO operates only when user issues a single semop
operation and not an array of opretions.
SETFIFO is the default for backward compatbility.
Signed-off-by: raz <raziebe@xxxxxxxxx>
---
ipc/sem.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++--
1 files changed, 49 insertions(+), 2 deletions(-)
diff --git a/ipc/sem.c b/ipc/sem.c
index 90dc5a1..921056d 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1343,6 +1343,51 @@ static int get_queue_result(struct sem_queue *q)
return error;
}
+/*
+ * find the best place to put the task sorted by rt prio
+*/
+static struct list_head *find_pos(struct sem *curr, int alter,
+ struct task_struct *p)
+{
+ struct sem_queue *q;
+ struct sem_queue *ret_pos = NULL;
+ struct list_head *tasks_queue = &curr->sem_pending;
+
+ if (!alter)
+ return tasks_queue;
+
+ if (!(curr->flags & PRIO_SEM))
+ return tasks_queue;
+ /*
+ * make no effort to sort SCHED_OTHER,
+ * just push task to the back of the queue.
+ */
+ if (!(p->policy == SCHED_FIFO || p->policy == SCHED_RR))
+ return tasks_queue;
+ /*
+ * make no distinction between SCHED_FIFO
+ * and SCHED_RR policies.
+ */
+ list_for_each_entry(q, tasks_queue, simple_list) {
+ struct task_struct *t;
+
+ t = q->sleeper;
+ if (current->rt_priority == t->rt_priority) {
+ /*
+ * push in a FIFO manner
+ * tasks in same priority
+ */
+ ret_pos = q;
+ continue;
+ }
+ if (current->rt_priority < t->rt_priority)
+ continue;
+ return &q->simple_list;
+ }
+ if (ret_pos)
+ return ret_pos->simple_list.next;
+ return tasks_queue;
+}
SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
unsigned, nsops, const struct timespec __user *, timeout)
@@ -1357,6 +1402,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
unsigned long jiffies_left = 0;
struct ipc_namespace *ns;
struct list_head tasks;
+ struct list_head *pending_pos;
ns = current->nsproxy->ipc_ns;
@@ -1478,10 +1524,11 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
struct sem *curr;
curr = &sma->sem_base[sops->sem_num];
+ pending_pos = find_pos(curr, alter, current);
if (alter)
- list_add_tail(&queue.simple_list, &curr->sem_pending);
+ list_add_tail(&queue.simple_list, pending_pos);
else
- list_add(&queue.simple_list, &curr->sem_pending);
+ list_add(&queue.simple_list, pending_pos);
} else {
INIT_LIST_HEAD(&queue.simple_list);
sma->complex_count++;
--
1.7.5.4
--
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