[RFC/PATCH] FUSYN 11/11: Modifications to the core: scheduler

From: inaky . perez-gonzalez
Date: Fri Jul 23 2004 - 11:09:32 EST

Add support for priority boosting, hooks into the scheduling
code.

As we modify the task struct, fix the init_task. Currently
ugly as hell, needs to be improved.


arch/i386/kernel/init_task.c | 1
include/linux/init_task.h | 31 ++++++++++++
include/linux/sched.h | 22 ++++++++-
kernel/exit.c | 2
kernel/fork.c | 2
kernel/sched.c | 103 +++++++++++++++++++++++++++++++++++++------
kernel/signal.c | 14 +++++
7 files changed, 160 insertions(+), 15 deletions(-)

--- include/linux/init_task.h:1.1.1.5 Tue Apr 6 01:51:36 2004
+++ include/linux/init_task.h Wed May 26 22:14:47 2004
@@ -60,6 +60,32 @@
extern struct group_info init_groups;

/*
+ * Initialize the init task fuqueue's and fulock side
+ *
+ * Ugly as hell--any ideas on how to make this look better? The
+ * problem is that we remove stuff from the task struct when we
+ * disable FUSYN or FULOCK.
+ */
+#ifndef CONFIG_FUSYN
+# define FUQUEUE_INIT_TASK(a) /* Emtpy, nothing to init */
+#else /* #ifndef CONFIG_FUSYN */
+# define FUQUEUE_INIT_TASK(task) \
+ , /* Grumble, mumble, @od damn it */ \
+ .fuqueue_wait_lock = SPIN_LOCK_UNLOCKED, \
+ .fuqueue_wait = NULL, \
+ .fuqueue_waiter = NULL
+# ifndef CONFIG_FULOCK
+# define FULOCK_INIT_TASK(a) /* Emtpy, nothing to init */
+# else /* #ifndef CONFIG_FULOCK */
+# define FULOCK_INIT_TASK(task) \
+ , /* Grumble, mumble, @od damn it */ \
+ .fulock_olist = plist_INIT (&(task).fulock_olist, BOTTOM_PRIO), \
+ .fulock_olist_lock = SPIN_LOCK_UNLOCKED
+# endif
+#endif /* #ifndef CONFIG_FUSYN
+ */
+
+/*
* INIT_TASK is used to set up the first task table, touch at
* your own risk!. Base=0, limit=0x1fffff (=2MB)
*/
@@ -72,6 +98,7 @@
.lock_depth = -1, \
.prio = MAX_PRIO-20, \
.static_prio = MAX_PRIO-20, \
+ .boost_prio = BOTTOM_PRIO, \
.policy = SCHED_NORMAL, \
.cpus_allowed = CPU_MASK_ALL, \
.mm = NULL, \
@@ -111,7 +138,9 @@
.alloc_lock = SPIN_LOCK_UNLOCKED, \
.proc_lock = SPIN_LOCK_UNLOCKED, \
.switch_lock = SPIN_LOCK_UNLOCKED, \
- .journal_info = NULL, \
+ .journal_info = NULL \
+ FUQUEUE_INIT_TASK(tsk) \
+ FULOCK_INIT_TASK(tsk), \
}


--- include/linux/sched.h:1.1.1.14 Tue Apr 6 01:51:36 2004
+++ include/linux/sched.h Wed Jun 9 23:36:40 2004
@@ -29,6 +29,7 @@
#include <linux/completion.h>
#include <linux/pid.h>
#include <linux/percpu.h>
+#include <linux/plist.h> /* fulock ownership list */

struct exec_domain;

@@ -174,6 +175,9 @@

#define MAX_SCHEDULE_TIMEOUT LONG_MAX
extern signed long FASTCALL(schedule_timeout(signed long timeout));
+struct timeout;
+#define MAX_SCHEDULE_TIMEOUT_EXT ((struct timeout *) ~0)
+extern void FASTCALL(schedule_timeout_ext (const struct timeout *timeout));
asmlinkage void schedule(void);

struct namespace;
@@ -286,6 +290,7 @@
#define MAX_RT_PRIO MAX_USER_RT_PRIO

#define MAX_PRIO (MAX_RT_PRIO + 40)
+#define BOTTOM_PRIO INT_MAX

#define rt_task(p) ((p)->prio < MAX_RT_PRIO)

@@ -330,6 +335,8 @@
};


+struct fuqueue;
+struct fuqueue_waiter;
struct io_context; /* See blkdev.h */
void exit_io_context(void);

@@ -369,7 +376,7 @@

int lock_depth; /* Lock depth */

- int prio, static_prio;
+ int prio, static_prio, boost_prio;
struct list_head run_list;
prio_array_t *array;

@@ -493,6 +500,15 @@

unsigned long ptrace_message;
siginfo_t *last_siginfo; /* For ptrace use. */
+#ifdef CONFIG_FUSYN /* FIXME: I don't really like this... */
+ struct fuqueue *fuqueue_wait; /* waiting for this qeueue */
+ struct fuqueue_waiter *fuqueue_waiter; /* waiting for this qeueue */
+ spinlock_t fuqueue_wait_lock;
+#endif
+#ifdef CONFIG_FULOCK /* FIXME: I don't really like this... */
+ struct plist fulock_olist; /* Fulock ownership list */
+ spinlock_t fulock_olist_lock;
+#endif
};

static inline pid_t process_group(struct task_struct *tsk)
@@ -557,6 +573,9 @@
extern int task_curr(task_t *p);
extern int idle_cpu(int cpu);

+/* Set the boost priority */
+extern unsigned __prio_boost (task_t *, int);
+
void yield(void);

/*
@@ -599,6 +618,7 @@
extern unsigned long itimer_next;
extern void do_timer(struct pt_regs *);

+extern int try_to_wake_up(struct task_struct *p, unsigned int state, int sync);
extern int FASTCALL(wake_up_state(struct task_struct * tsk, unsigned int state));
extern int FASTCALL(wake_up_process(struct task_struct * tsk));
#ifdef CONFIG_SMP
--- kernel/exit.c:1.1.1.11 Tue Apr 6 01:51:37 2004
+++ kernel/exit.c Wed May 26 22:14:57 2004
@@ -22,6 +22,7 @@
#include <linux/profile.h>
#include <linux/mount.h>
#include <linux/proc_fs.h>
+#include <linux/fulock.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
@@ -771,6 +772,7 @@
}

acct_process(code);
+ exit_fulocks(tsk);
__exit_mm(tsk);

exit_sem(tsk);
--- kernel/fork.c:1.1.1.14 Tue Apr 6 01:51:37 2004
+++ kernel/fork.c Wed May 26 22:14:57 2004
@@ -31,6 +31,7 @@
#include <linux/futex.h>
#include <linux/ptrace.h>
#include <linux/mount.h>
+#include <linux/fulock.h>

#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -964,6 +965,7 @@
goto bad_fork_cleanup_signal;
if ((retval = copy_namespace(clone_flags, p)))
goto bad_fork_cleanup_mm;
+ init_fulocks(p);
retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
if (retval)
goto bad_fork_cleanup_namespace;
--- kernel/sched.c:1.1.1.18 Tue Apr 6 01:51:37 2004
+++ kernel/sched.c Wed Jun 23 00:07:06 2004
@@ -33,6 +33,7 @@
#include <linux/suspend.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
+#include <linux/fuqueue.h>
#include <linux/smp.h>
#include <linux/timer.h>
#include <linux/rcupdate.h>
@@ -356,13 +357,10 @@
*
* Both properties are important to certain workloads.
*/
-static int effective_prio(task_t *p)
+static inline int __effective_prio(task_t *p)
{
int bonus, prio;

- if (rt_task(p))
- return p->prio;
-
bonus = CURRENT_BONUS(p) - MAX_BONUS / 2;

prio = p->static_prio - bonus;
@@ -372,6 +370,13 @@
prio = MAX_PRIO-1;
return prio;
}
+static int effective_prio(task_t *p)
+{
+ int new_prio;
+ new_prio = rt_task(p)? p->prio : __effective_prio(p);
+ return min (new_prio, p->boost_prio);
+}
+

/*
* __activate_task - move a task to the runqueue.
@@ -647,7 +652,7 @@
*
* returns failure only if the task is already active.
*/
-static int try_to_wake_up(task_t * p, unsigned int state, int sync)
+int try_to_wake_up(task_t * p, unsigned int state, int sync)
{
unsigned long flags;
int success = 0;
@@ -733,6 +738,8 @@
*/
p->thread_info->preempt_count = 1;
#endif
+ /* Initially the task has no priority boosting */
+ p->boost_prio = BOTTOM_PRIO;
/*
* Share the timeslice between parent and child, thus the
* total amount of pending timeslices in the system doesn't change,
@@ -1772,6 +1779,9 @@
* There are circumstances in which we can try to wake a task which has already
* started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
* zero in this (rare) case, and we handle it by continuing to scan the queue.
+ *
+ * fuqueue_wait_cancel needs to hook up here to properly rescheduler
+ * priority inheritance/protected tasks. Check its doc to learn why.
*/
static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
int nr_exclusive, int sync)
@@ -1783,6 +1793,7 @@
unsigned flags;
curr = list_entry(tmp, wait_queue_t, task_list);
flags = curr->flags;
+ fuqueue_waiter_cancel(curr->task, -EINTR);
if (curr->func(curr, mode, sync) &&
(flags & WQ_FLAG_EXCLUSIVE) &&
!--nr_exclusive)
@@ -1965,12 +1976,17 @@

void scheduling_functions_end_here(void) { }

+/*
+ * Note the initialization of old_prio and new_dynamic_prio. If we
+ * fall back through 'out_unlock', they will help to skip the call to
+ * fuqueue_waiter_chprio().
+ */
void set_user_nice(task_t *p, long nice)
{
unsigned long flags;
prio_array_t *array;
runqueue_t *rq;
- int old_prio, new_prio, delta;
+ int old_prio = p->prio, new_prio, delta;

if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
return;
@@ -1993,11 +2009,12 @@
if (array)
dequeue_task(p, array);

- old_prio = p->prio;
new_prio = NICE_TO_PRIO(nice);
delta = new_prio - old_prio;
p->static_prio = NICE_TO_PRIO(nice);
p->prio += delta;
+ old_prio = p->prio;
+ p->prio = min (p->prio, p->boost_prio);

if (array) {
enqueue_task(p, array);
@@ -2010,6 +2027,7 @@
}
out_unlock:
task_rq_unlock(rq, &flags);
+ fuqueue_waiter_chprio(p, old_prio);
}

EXPORT_SYMBOL(set_user_nice);
@@ -2102,20 +2120,79 @@
return pid ? find_task_by_pid(pid) : current;
}

+
+/**
+ * Boost the priority of a task from a new dynamic priority.
+ *
+ * On SCHED_NORMAL, sets boost_prio in as __effective_prio()
+ * would do to get the same prio when it is reinserted in the list.
+ *
+ * @p: Pointer to the task in question
+ * @prio: New boost priority to set
+ * @returns: !0 if the final new dynamic priority of the task has
+ * changed, 0 otherwise.
+ *
+ * This does not do fuqueue priority propagation (to avoid infinite
+ * recursion in the fuqueue code).
+ */
+unsigned __prio_boost(task_t *p, int prio)
+{
+ runqueue_t *rq;
+ prio_array_t *array;
+ long flags;
+ int old_prio, new_dynamic_prio, newprio;
+
+ if (p->boost_prio == prio)
+ return 0;
+
+ rq = task_rq_lock(p, &flags);
+ old_prio = p->prio;
+ array = p->array;
+ if (array)
+ deactivate_task(p, task_rq(p));
+ p->boost_prio = prio;
+ new_dynamic_prio = p->policy != SCHED_NORMAL?
+ MAX_USER_RT_PRIO - 1 - p->rt_priority
+ : __effective_prio(p);
+ newprio = min (new_dynamic_prio, p->boost_prio);
+ p->prio = newprio;
+ if (array) {
+ __activate_task(p, task_rq(p));
+ if (rq->curr == p) {
+ if (p->prio > old_prio)
+ resched_task(rq->curr);
+ }
+ else if (TASK_PREEMPTS_CURR (p, rq))
+ resched_task(rq->curr);
+ }
+ task_rq_unlock (rq, &flags);
+ return old_prio != newprio;
+}
+
+
/* Actually do priority change: must hold rq lock. */
static void __setscheduler(struct task_struct *p, int policy, int prio)
{
+ int newprio, oldprio;
+
BUG_ON(p->array);
p->policy = policy;
p->rt_priority = prio;
if (policy != SCHED_NORMAL)
- p->prio = MAX_USER_RT_PRIO-1 - p->rt_priority;
+ newprio = MAX_USER_RT_PRIO-1 - p->rt_priority;
else
- p->prio = p->static_prio;
+ newprio = p->static_prio;
+ oldprio = p->prio;
+ p->prio = min (newprio, p->boost_prio);
}

/*
* setscheduler - change the scheduling policy and/or RT priority of a thread.
+ *
+ * Note the initialization of old_prio. If we fall back through
+ * 'out_unlock*', it will help to skip the call to
+ * fuqueue_waiter_chprio(); this way we avoid the extra check on
+ * 'retval == 0'.
*/
static int setscheduler(pid_t pid, int policy, struct sched_param __user *param)
{
@@ -2150,7 +2227,7 @@
* runqueue lock must be held.
*/
rq = task_rq_lock(p, &flags);
-
+ oldprio = p->prio;
if (policy < 0)
policy = p->policy;
else {
@@ -2186,7 +2263,6 @@
if (array)
deactivate_task(p, task_rq(p));
retval = 0;
- oldprio = p->prio;
__setscheduler(p, policy, lp.sched_priority);
if (array) {
__activate_task(p, task_rq(p));
@@ -2204,9 +2280,9 @@

out_unlock:
task_rq_unlock(rq, &flags);
+ fuqueue_waiter_chprio(p, oldprio);
out_unlock_tasklist:
read_unlock_irq(&tasklist_lock);
-
out_nounlock:
return retval;
}
@@ -2868,6 +2944,7 @@
struct task_struct *p;
struct runqueue *rq;
unsigned long flags;
+ unsigned old_prio;

switch (action) {
case CPU_UP_PREPARE:
@@ -2877,8 +2954,10 @@
kthread_bind(p, cpu);
/* Must be high prio: stop_machine expects to yield to it. */
rq = task_rq_lock(p, &flags);
+ old_prio = p->prio;
__setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
task_rq_unlock(rq, &flags);
+ fuqueue_waiter_chprio(p, old_prio);
cpu_rq(cpu)->migration_thread = p;
break;
case CPU_ONLINE:
--- kernel/signal.c:1.1.1.12 Tue Apr 6 01:51:37 2004
+++ kernel/signal.c Wed Jun 23 00:06:23 2004
@@ -21,6 +21,7 @@
#include <linux/binfmts.h>
#include <linux/security.h>
#include <linux/ptrace.h>
+#include <linux/fuqueue.h>
#include <asm/param.h>
#include <asm/uaccess.h>
#include <asm/siginfo.h>
@@ -521,6 +522,7 @@
return signr;
}

+
/*
* Tell a process that it has a new active signal..
*
@@ -544,12 +546,20 @@
* executing another processor and just now entering stopped state.
* By calling wake_up_process any time resume is set, we ensure
* the process will wake up and handle its stop or death signal.
+ *
+ * fuqueue_waiter_cancel needs to hook up here to properly rescheduler
+ * priority inheritance/protected tasks. The reason is that
+ * when we resched a process that has boosted another one, we
+ * need to kick its butt off the CPU (and lower its priority) ASAP
+ * so that 't' can run.
*/
mask = TASK_INTERRUPTIBLE;
if (resume)
mask |= TASK_STOPPED;
- if (!wake_up_state(t, mask))
+ fuqueue_waiter_cancel(t, -EINTR);
+ if (!wake_up_state(t, mask)) {
kick_process(t);
+ }
}

/*
@@ -672,6 +682,8 @@
set_tsk_thread_flag(t, TIF_SIGPENDING);
state |= TASK_INTERRUPTIBLE;
}
+ /* FIXME: I am not that sure we need to cancel here */
+ fuqueue_waiter_cancel(t, -EINTR);
wake_up_state(t, state);

t = next_thread(t);
--- arch/i386/kernel/init_task.c:1.1.1.4 Tue Apr 6 00:21:44 2004
+++ arch/i386/kernel/init_task.c Wed May 26 21:14:03 2004
@@ -4,6 +4,7 @@
#include <linux/init.h>
#include <linux/init_task.h>
#include <linux/fs.h>
+#include <linux/fuqueue.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
-
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