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/*
* Mach Operating System
* Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
* All Rights Reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*/
/*
*
* File: kern/thread_swap.c
* Author: Avadis Tevanian, Jr.
* Date: 1987
*
* Mach thread swapper:
* Find idle threads to swap, freeing up kernel stack resources
* at the expense of allowing them to execute.
*
* Swap in threads that need to be run. This is done here
* by the swapper thread since it cannot be done (in general)
* when the kernel tries to place a thread on a run queue.
*
* Note: The act of swapping a thread in Mach does not mean that
* its memory gets forcibly swapped to secondary storage. The memory
* for the task corresponding to a swapped thread is paged out
* through the normal paging mechanism.
*
*/
#include <ipc/ipc_kmsg.h>
#include <kern/counters.h>
#include <kern/debug.h>
#include <kern/thread.h>
#include <kern/lock.h>
#include <vm/vm_map.h>
#include <vm/vm_kern.h>
#include <mach/vm_param.h>
#include <kern/sched_prim.h>
#include <kern/processor.h>
#include <kern/thread_swap.h>
#include <machine/machspl.h> /* for splsched */
queue_head_t swapin_queue;
decl_simple_lock_data(, swapper_lock_data)
#define swapper_lock() simple_lock(&swapper_lock_data)
#define swapper_unlock() simple_unlock(&swapper_lock_data)
/*
* swapper_init: [exported]
*
* Initialize the swapper module.
*/
void swapper_init(void)
{
queue_init(&swapin_queue);
simple_lock_init(&swapper_lock_data);
}
/*
* thread_swapin: [exported]
*
* Place the specified thread in the list of threads to swapin. It
* is assumed that the thread is locked, therefore we are at splsched.
*
* We don't bother with stack_alloc_try to optimize swapin;
* our callers have already tried that route.
*/
void thread_swapin(thread_t thread)
{
switch (thread->state & TH_SWAP_STATE) {
case TH_SWAPPED:
/*
* Swapped out - queue for swapin thread.
*/
thread->state = (thread->state & ~TH_SWAP_STATE)
| TH_SW_COMING_IN;
swapper_lock();
enqueue_tail(&swapin_queue, &(thread->links));
swapper_unlock();
thread_wakeup((event_t) &swapin_queue);
break;
case TH_SW_COMING_IN:
/*
* Already queued for swapin thread, or being
* swapped in.
*/
break;
default:
/*
* Already swapped in.
*/
panic("thread_swapin");
}
}
/*
* thread_doswapin:
*
* Swapin the specified thread, if it should be runnable, then put
* it on a run queue. No locks should be held on entry, as it is
* likely that this routine will sleep (waiting for stack allocation).
*/
kern_return_t thread_doswapin(thread_t thread)
{
kern_return_t kr;
spl_t s;
/*
* Allocate the kernel stack.
*/
kr = stack_alloc(thread, thread_continue);
if (kr != KERN_SUCCESS)
return kr;
/*
* Place on run queue.
*/
s = splsched();
thread_lock(thread);
thread->state &= ~(TH_SWAPPED | TH_SW_COMING_IN);
if (thread->state & TH_RUN)
thread_setrun(thread, TRUE);
thread_unlock(thread);
(void) splx(s);
return KERN_SUCCESS;
}
/*
* swapin_thread: [exported]
*
* This procedure executes as a kernel thread. Threads that need to
* be swapped in are swapped in by this thread.
*/
void __attribute__((noreturn)) swapin_thread_continue(void)
{
for (;;) {
thread_t thread;
spl_t s;
s = splsched();
swapper_lock();
while ((thread = (thread_t) dequeue_head(&swapin_queue))
!= THREAD_NULL) {
kern_return_t kr;
swapper_unlock();
(void) splx(s);
kr = thread_doswapin(thread); /* may block */
s = splsched();
swapper_lock();
if (kr != KERN_SUCCESS) {
enqueue_head(&swapin_queue,
(queue_entry_t) thread);
break;
}
}
assert_wait((event_t) &swapin_queue, FALSE);
swapper_unlock();
(void) splx(s);
counter(c_swapin_thread_block++);
thread_block(swapin_thread_continue);
}
}
void swapin_thread(void)
{
stack_privilege(current_thread());
swapin_thread_continue();
/*NOTREACHED*/
}
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