blob: 8360fa3f676df2ec0e051235bb5aebea68cc9f83 [file] [log] [blame]
Jeff Dike2ea5bc52007-05-10 22:22:32 -07001/*
Anton Ivanovff6a1792017-11-20 21:17:58 +00002 * Copyright (C) 2017 - Cambridge Greys Ltd
3 * Copyright (C) 2011 - 2014 Cisco Systems Inc
Jeff Dikeba180fd2007-10-16 01:27:00 -07004 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
Linus Torvalds1da177e2005-04-16 15:20:36 -07005 * Licensed under the GPL
6 * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
7 * Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
8 */
9
Al Viro37185b32012-10-08 03:27:32 +010010#include <linux/cpumask.h>
11#include <linux/hardirq.h>
12#include <linux/interrupt.h>
13#include <linux/kernel_stat.h>
14#include <linux/module.h>
15#include <linux/sched.h>
16#include <linux/seq_file.h>
17#include <linux/slab.h>
18#include <as-layout.h>
19#include <kern_util.h>
20#include <os.h>
Anton Ivanovff6a1792017-11-20 21:17:58 +000021#include <irq_user.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070022
Anton Ivanovff6a1792017-11-20 21:17:58 +000023
24/* When epoll triggers we do not know why it did so
25 * we can also have different IRQs for read and write.
26 * This is why we keep a small irq_fd array for each fd -
27 * one entry per IRQ type
Jeff Diked973a772007-05-06 14:51:27 -070028 */
Jeff Dike9b4f0182006-03-27 01:14:31 -080029
Anton Ivanovff6a1792017-11-20 21:17:58 +000030struct irq_entry {
31 struct irq_entry *next;
32 int fd;
33 struct irq_fd *irq_array[MAX_IRQ_TYPE + 1];
34};
Jeff Dike9b4f0182006-03-27 01:14:31 -080035
Anton Ivanovff6a1792017-11-20 21:17:58 +000036static struct irq_entry *active_fds;
Jeff Dike9b4f0182006-03-27 01:14:31 -080037
Jeff Dikebfaafd72006-07-10 04:45:10 -070038static DEFINE_SPINLOCK(irq_lock);
39
Anton Ivanovff6a1792017-11-20 21:17:58 +000040static void irq_io_loop(struct irq_fd *irq, struct uml_pt_regs *regs)
41{
42/*
43 * irq->active guards against reentry
44 * irq->pending accumulates pending requests
45 * if pending is raised the irq_handler is re-run
46 * until pending is cleared
47 */
48 if (irq->active) {
49 irq->active = false;
50 do {
51 irq->pending = false;
52 do_IRQ(irq->irq, regs);
53 } while (irq->pending && (!irq->purge));
54 if (!irq->purge)
55 irq->active = true;
56 } else {
57 irq->pending = true;
58 }
59}
60
61void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
62{
63 struct irq_entry *irq_entry;
64 struct irq_fd *irq;
65
66 int n, i, j;
67
68 while (1) {
69 /* This is now lockless - epoll keeps back-referencesto the irqs
70 * which have trigger it so there is no need to walk the irq
71 * list and lock it every time. We avoid locking by turning off
72 * IO for a specific fd by executing os_del_epoll_fd(fd) before
73 * we do any changes to the actual data structures
74 */
75 n = os_waiting_for_events_epoll();
76
77 if (n <= 0) {
78 if (n == -EINTR)
79 continue;
80 else
81 break;
82 }
83
84 for (i = 0; i < n ; i++) {
85 /* Epoll back reference is the entry with 3 irq_fd
86 * leaves - one for each irq type.
87 */
88 irq_entry = (struct irq_entry *)
89 os_epoll_get_data_pointer(i);
90 for (j = 0; j < MAX_IRQ_TYPE ; j++) {
91 irq = irq_entry->irq_array[j];
92 if (irq == NULL)
93 continue;
94 if (os_epoll_triggered(i, irq->events) > 0)
95 irq_io_loop(irq, regs);
96 if (irq->purge) {
97 irq_entry->irq_array[j] = NULL;
98 kfree(irq);
99 }
100 }
101 }
102 }
103}
104
105static int assign_epoll_events_to_irq(struct irq_entry *irq_entry)
106{
107 int i;
108 int events = 0;
109 struct irq_fd *irq;
110
111 for (i = 0; i < MAX_IRQ_TYPE ; i++) {
112 irq = irq_entry->irq_array[i];
113 if (irq != NULL)
114 events = irq->events | events;
115 }
116 if (events > 0) {
117 /* os_add_epoll will call os_mod_epoll if this already exists */
118 return os_add_epoll_fd(events, irq_entry->fd, irq_entry);
119 }
120 /* No events - delete */
121 return os_del_epoll_fd(irq_entry->fd);
122}
123
124
125
WANG Cong4c182ae2008-07-23 21:28:47 -0700126static int activate_fd(int irq, int fd, int type, void *dev_id)
Jeff Dike9b4f0182006-03-27 01:14:31 -0800127{
Anton Ivanovff6a1792017-11-20 21:17:58 +0000128 struct irq_fd *new_fd;
129 struct irq_entry *irq_entry;
130 int i, err, events;
Jeff Dike9b4f0182006-03-27 01:14:31 -0800131 unsigned long flags;
Jeff Dike9b4f0182006-03-27 01:14:31 -0800132
Jeff Dikebf8fde72008-02-04 22:31:04 -0800133 err = os_set_fd_async(fd);
Jesper Juhl191ef962006-05-01 12:15:57 -0700134 if (err < 0)
Jeff Dike9b4f0182006-03-27 01:14:31 -0800135 goto out;
136
Anton Ivanovff6a1792017-11-20 21:17:58 +0000137 spin_lock_irqsave(&irq_lock, flags);
Jeff Dike9b4f0182006-03-27 01:14:31 -0800138
Anton Ivanovff6a1792017-11-20 21:17:58 +0000139 /* Check if we have an entry for this fd */
Jeff Dike9b4f0182006-03-27 01:14:31 -0800140
Paolo 'Blaisorblade' Giarrusso0f978692007-03-07 20:41:13 -0800141 err = -EBUSY;
Anton Ivanovff6a1792017-11-20 21:17:58 +0000142 for (irq_entry = active_fds;
143 irq_entry != NULL; irq_entry = irq_entry->next) {
144 if (irq_entry->fd == fd)
145 break;
146 }
147
148 if (irq_entry == NULL) {
149 /* This needs to be atomic as it may be called from an
150 * IRQ context.
151 */
152 irq_entry = kmalloc(sizeof(struct irq_entry), GFP_ATOMIC);
153 if (irq_entry == NULL) {
154 printk(KERN_ERR
155 "Failed to allocate new IRQ entry\n");
Jeff Dike9b4f0182006-03-27 01:14:31 -0800156 goto out_unlock;
157 }
Anton Ivanovff6a1792017-11-20 21:17:58 +0000158 irq_entry->fd = fd;
159 for (i = 0; i < MAX_IRQ_TYPE; i++)
160 irq_entry->irq_array[i] = NULL;
161 irq_entry->next = active_fds;
162 active_fds = irq_entry;
Jeff Dike9b4f0182006-03-27 01:14:31 -0800163 }
164
Anton Ivanovff6a1792017-11-20 21:17:58 +0000165 /* Check if we are trying to re-register an interrupt for a
166 * particular fd
Jeff Dike9b4f0182006-03-27 01:14:31 -0800167 */
Anton Ivanovff6a1792017-11-20 21:17:58 +0000168
169 if (irq_entry->irq_array[type] != NULL) {
170 printk(KERN_ERR
171 "Trying to reregister IRQ %d FD %d TYPE %d ID %p\n",
172 irq, fd, type, dev_id
173 );
174 goto out_unlock;
175 } else {
176 /* New entry for this fd */
177
178 err = -ENOMEM;
179 new_fd = kmalloc(sizeof(struct irq_fd), GFP_ATOMIC);
180 if (new_fd == NULL)
181 goto out_unlock;
182
183 events = os_event_mask(type);
184
185 *new_fd = ((struct irq_fd) {
186 .id = dev_id,
187 .irq = irq,
188 .type = type,
189 .events = events,
190 .active = true,
191 .pending = false,
192 .purge = false
193 });
194 /* Turn off any IO on this fd - allows us to
195 * avoid locking the IRQ loop
196 */
197 os_del_epoll_fd(irq_entry->fd);
198 irq_entry->irq_array[type] = new_fd;
199 }
200
201 /* Turn back IO on with the correct (new) IO event mask */
202 assign_epoll_events_to_irq(irq_entry);
203 spin_unlock_irqrestore(&irq_lock, flags);
204 maybe_sigio_broken(fd, (type != IRQ_NONE));
Jeff Dike9b4f0182006-03-27 01:14:31 -0800205
Jeff Dike19bdf042006-09-25 23:33:04 -0700206 return 0;
Anton Ivanovff6a1792017-11-20 21:17:58 +0000207out_unlock:
Jeff Dikebfaafd72006-07-10 04:45:10 -0700208 spin_unlock_irqrestore(&irq_lock, flags);
Anton Ivanovff6a1792017-11-20 21:17:58 +0000209out:
Jeff Dike19bdf042006-09-25 23:33:04 -0700210 return err;
Jeff Dike9b4f0182006-03-27 01:14:31 -0800211}
212
Anton Ivanovff6a1792017-11-20 21:17:58 +0000213/*
214 * Walk the IRQ list and dispose of any unused entries.
215 * Should be done under irq_lock.
216 */
Jeff Dike9b4f0182006-03-27 01:14:31 -0800217
Anton Ivanovff6a1792017-11-20 21:17:58 +0000218static void garbage_collect_irq_entries(void)
219{
220 int i;
221 bool reap;
222 struct irq_entry *walk;
223 struct irq_entry *previous = NULL;
224 struct irq_entry *to_free;
225
226 if (active_fds == NULL)
227 return;
228 walk = active_fds;
229 while (walk != NULL) {
230 reap = true;
231 for (i = 0; i < MAX_IRQ_TYPE ; i++) {
232 if (walk->irq_array[i] != NULL) {
233 reap = false;
234 break;
235 }
236 }
237 if (reap) {
238 if (previous == NULL)
239 active_fds = walk->next;
240 else
241 previous->next = walk->next;
242 to_free = walk;
243 } else {
244 to_free = NULL;
245 }
246 walk = walk->next;
YueHaibingd312a252018-08-03 14:39:11 +0800247 kfree(to_free);
Anton Ivanovff6a1792017-11-20 21:17:58 +0000248 }
Jeff Dike9b4f0182006-03-27 01:14:31 -0800249}
250
Anton Ivanovff6a1792017-11-20 21:17:58 +0000251/*
252 * Walk the IRQ list and get the descriptor for our FD
253 */
Jeff Dike9b4f0182006-03-27 01:14:31 -0800254
Anton Ivanovff6a1792017-11-20 21:17:58 +0000255static struct irq_entry *get_irq_entry_by_fd(int fd)
Jeff Dike9b4f0182006-03-27 01:14:31 -0800256{
Anton Ivanovff6a1792017-11-20 21:17:58 +0000257 struct irq_entry *walk = active_fds;
Jeff Dike9b4f0182006-03-27 01:14:31 -0800258
Anton Ivanovff6a1792017-11-20 21:17:58 +0000259 while (walk != NULL) {
260 if (walk->fd == fd)
261 return walk;
262 walk = walk->next;
263 }
264 return NULL;
Jeff Dike9b4f0182006-03-27 01:14:31 -0800265}
266
Jeff Dike9b4f0182006-03-27 01:14:31 -0800267
Anton Ivanovff6a1792017-11-20 21:17:58 +0000268/*
269 * Walk the IRQ list and dispose of an entry for a specific
270 * device, fd and number. Note - if sharing an IRQ for read
271 * and writefor the same FD it will be disposed in either case.
272 * If this behaviour is undesirable use different IRQ ids.
273 */
Jeff Dike9b4f0182006-03-27 01:14:31 -0800274
Anton Ivanovff6a1792017-11-20 21:17:58 +0000275#define IGNORE_IRQ 1
276#define IGNORE_DEV (1<<1)
277
278static void do_free_by_irq_and_dev(
279 struct irq_entry *irq_entry,
280 unsigned int irq,
281 void *dev,
282 int flags
283)
Jeff Dike9b4f0182006-03-27 01:14:31 -0800284{
Anton Ivanovff6a1792017-11-20 21:17:58 +0000285 int i;
286 struct irq_fd *to_free;
287
288 for (i = 0; i < MAX_IRQ_TYPE ; i++) {
289 if (irq_entry->irq_array[i] != NULL) {
290 if (
291 ((flags & IGNORE_IRQ) ||
292 (irq_entry->irq_array[i]->irq == irq)) &&
293 ((flags & IGNORE_DEV) ||
294 (irq_entry->irq_array[i]->id == dev))
295 ) {
296 /* Turn off any IO on this fd - allows us to
297 * avoid locking the IRQ loop
298 */
299 os_del_epoll_fd(irq_entry->fd);
300 to_free = irq_entry->irq_array[i];
301 irq_entry->irq_array[i] = NULL;
302 assign_epoll_events_to_irq(irq_entry);
303 if (to_free->active)
304 to_free->purge = true;
305 else
306 kfree(to_free);
307 }
308 }
309 }
Jeff Dike9b4f0182006-03-27 01:14:31 -0800310}
311
312void free_irq_by_fd(int fd)
313{
Anton Ivanovff6a1792017-11-20 21:17:58 +0000314 struct irq_entry *to_free;
315 unsigned long flags;
316
317 spin_lock_irqsave(&irq_lock, flags);
318 to_free = get_irq_entry_by_fd(fd);
319 if (to_free != NULL) {
320 do_free_by_irq_and_dev(
321 to_free,
322 -1,
323 NULL,
324 IGNORE_IRQ | IGNORE_DEV
325 );
326 }
327 garbage_collect_irq_entries();
328 spin_unlock_irqrestore(&irq_lock, flags);
Jeff Dike9b4f0182006-03-27 01:14:31 -0800329}
Anton Ivanovf1668502017-11-22 13:49:55 +0000330EXPORT_SYMBOL(free_irq_by_fd);
Jeff Dike9b4f0182006-03-27 01:14:31 -0800331
Anton Ivanovff6a1792017-11-20 21:17:58 +0000332static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
Jeff Dike9b4f0182006-03-27 01:14:31 -0800333{
Anton Ivanovff6a1792017-11-20 21:17:58 +0000334 struct irq_entry *to_free;
335 unsigned long flags;
Jeff Dike9b4f0182006-03-27 01:14:31 -0800336
Anton Ivanovff6a1792017-11-20 21:17:58 +0000337 spin_lock_irqsave(&irq_lock, flags);
338 to_free = active_fds;
339 while (to_free != NULL) {
340 do_free_by_irq_and_dev(
341 to_free,
342 irq,
343 dev,
344 0
345 );
346 to_free = to_free->next;
Jeff Dike9b4f0182006-03-27 01:14:31 -0800347 }
Anton Ivanovff6a1792017-11-20 21:17:58 +0000348 garbage_collect_irq_entries();
349 spin_unlock_irqrestore(&irq_lock, flags);
Jeff Dike9b4f0182006-03-27 01:14:31 -0800350}
351
Anton Ivanovff6a1792017-11-20 21:17:58 +0000352
Jeff Dike9b4f0182006-03-27 01:14:31 -0800353void reactivate_fd(int fd, int irqnum)
354{
Anton Ivanovff6a1792017-11-20 21:17:58 +0000355 /** NOP - we do auto-EOI now **/
Jeff Dike9b4f0182006-03-27 01:14:31 -0800356}
357
358void deactivate_fd(int fd, int irqnum)
359{
Anton Ivanovff6a1792017-11-20 21:17:58 +0000360 struct irq_entry *to_free;
Jeff Dike9b4f0182006-03-27 01:14:31 -0800361 unsigned long flags;
Jeff Dike9b4f0182006-03-27 01:14:31 -0800362
Anton Ivanovff6a1792017-11-20 21:17:58 +0000363 os_del_epoll_fd(fd);
Jeff Dikebfaafd72006-07-10 04:45:10 -0700364 spin_lock_irqsave(&irq_lock, flags);
Anton Ivanovff6a1792017-11-20 21:17:58 +0000365 to_free = get_irq_entry_by_fd(fd);
366 if (to_free != NULL) {
367 do_free_by_irq_and_dev(
368 to_free,
369 irqnum,
370 NULL,
371 IGNORE_DEV
372 );
Jeff Dike19bdf042006-09-25 23:33:04 -0700373 }
Anton Ivanovff6a1792017-11-20 21:17:58 +0000374 garbage_collect_irq_entries();
Jeff Dikebfaafd72006-07-10 04:45:10 -0700375 spin_unlock_irqrestore(&irq_lock, flags);
Jeff Dike19bdf042006-09-25 23:33:04 -0700376 ignore_sigio_fd(fd);
Jeff Dike9b4f0182006-03-27 01:14:31 -0800377}
Al Viro73395a02011-08-18 20:14:10 +0100378EXPORT_SYMBOL(deactivate_fd);
Jeff Dike9b4f0182006-03-27 01:14:31 -0800379
Jeff Diked973a772007-05-06 14:51:27 -0700380/*
381 * Called just before shutdown in order to provide a clean exec
382 * environment in case the system is rebooting. No locking because
383 * that would cause a pointless shutdown hang if something hadn't
384 * released the lock.
385 */
Jeff Dike9b4f0182006-03-27 01:14:31 -0800386int deactivate_all_fds(void)
387{
Anton Ivanovff6a1792017-11-20 21:17:58 +0000388 unsigned long flags;
389 struct irq_entry *to_free;
Jeff Dike9b4f0182006-03-27 01:14:31 -0800390
Anton Ivanovff6a1792017-11-20 21:17:58 +0000391 spin_lock_irqsave(&irq_lock, flags);
392 /* Stop IO. The IRQ loop has no lock so this is our
393 * only way of making sure we are safe to dispose
394 * of all IRQ handlers
395 */
Jeff Dike9b4f0182006-03-27 01:14:31 -0800396 os_set_ioignore();
Anton Ivanovff6a1792017-11-20 21:17:58 +0000397 to_free = active_fds;
398 while (to_free != NULL) {
399 do_free_by_irq_and_dev(
400 to_free,
401 -1,
402 NULL,
403 IGNORE_IRQ | IGNORE_DEV
404 );
405 to_free = to_free->next;
406 }
407 garbage_collect_irq_entries();
408 spin_unlock_irqrestore(&irq_lock, flags);
409 os_close_epoll_fd();
Jesper Juhl191ef962006-05-01 12:15:57 -0700410 return 0;
Jeff Dike9b4f0182006-03-27 01:14:31 -0800411}
412
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413/*
Simon Arlottb60745b2007-10-20 01:23:03 +0200414 * do_IRQ handles all normal device IRQs (the special
Linus Torvalds1da177e2005-04-16 15:20:36 -0700415 * SMP cross-CPU interrupts have their own specific
416 * handlers).
417 */
Jeff Dike77bf4402007-10-16 01:26:58 -0700418unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700419{
Al Viro7bea96f2006-10-08 22:49:34 +0100420 struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
421 irq_enter();
Richard Weinbergerbe76d812010-10-26 14:22:20 -0700422 generic_handle_irq(irq);
Al Viro7bea96f2006-10-08 22:49:34 +0100423 irq_exit();
424 set_irq_regs(old_regs);
425 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426}
427
Richard Weinbergerfa7a0442012-04-17 22:37:13 +0200428void um_free_irq(unsigned int irq, void *dev)
429{
430 free_irq_by_irq_and_dev(irq, dev);
431 free_irq(irq, dev);
432}
433EXPORT_SYMBOL(um_free_irq);
434
Linus Torvalds1da177e2005-04-16 15:20:36 -0700435int um_request_irq(unsigned int irq, int fd, int type,
David Howells40220c12006-10-09 12:19:47 +0100436 irq_handler_t handler,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700437 unsigned long irqflags, const char * devname,
438 void *dev_id)
439{
440 int err;
441
Jeff Dike9ac625a2007-11-14 17:00:23 -0800442 if (fd != -1) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700443 err = activate_fd(irq, fd, type, dev_id);
Jeff Dike9ac625a2007-11-14 17:00:23 -0800444 if (err)
445 return err;
446 }
447
448 return request_irq(irq, handler, irqflags, devname, dev_id);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700449}
Jeff Dike9ac625a2007-11-14 17:00:23 -0800450
Linus Torvalds1da177e2005-04-16 15:20:36 -0700451EXPORT_SYMBOL(um_request_irq);
452EXPORT_SYMBOL(reactivate_fd);
453
Jeff Dikeba180fd2007-10-16 01:27:00 -0700454/*
Thomas Gleixner1d119aa2011-02-06 22:45:34 +0000455 * irq_chip must define at least enable/disable and ack when
456 * the edge handler is used.
Jeff Dikeba180fd2007-10-16 01:27:00 -0700457 */
Thomas Gleixner1d119aa2011-02-06 22:45:34 +0000458static void dummy(struct irq_data *d)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700459{
460}
461
Paolo 'Blaisorblade' Giarrussodbce7062005-06-21 17:16:19 -0700462/* This is used for everything else than the timer. */
Thomas Gleixner6fa851c2009-06-16 15:33:29 -0700463static struct irq_chip normal_irq_type = {
Thomas Gleixnerd1ea13c2010-09-23 18:40:07 +0200464 .name = "SIGIO",
Thomas Gleixner1d119aa2011-02-06 22:45:34 +0000465 .irq_disable = dummy,
466 .irq_enable = dummy,
467 .irq_ack = dummy,
Richard Weinberger81bab4c2013-09-02 22:49:22 +0200468 .irq_mask = dummy,
469 .irq_unmask = dummy,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700470};
471
Thomas Gleixner6fa851c2009-06-16 15:33:29 -0700472static struct irq_chip SIGVTALRM_irq_type = {
Thomas Gleixnerd1ea13c2010-09-23 18:40:07 +0200473 .name = "SIGVTALRM",
Thomas Gleixner1d119aa2011-02-06 22:45:34 +0000474 .irq_disable = dummy,
475 .irq_enable = dummy,
476 .irq_ack = dummy,
Richard Weinberger81bab4c2013-09-02 22:49:22 +0200477 .irq_mask = dummy,
478 .irq_unmask = dummy,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700479};
480
481void __init init_IRQ(void)
482{
483 int i;
484
Thomas Gleixner0ebec352011-03-24 18:24:42 +0100485 irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
Richard Weinbergerbe76d812010-10-26 14:22:20 -0700486
Anton Ivanovff6a1792017-11-20 21:17:58 +0000487
Thomas Gleixner0ebec352011-03-24 18:24:42 +0100488 for (i = 1; i < NR_IRQS; i++)
489 irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
Anton Ivanovff6a1792017-11-20 21:17:58 +0000490 /* Initialize EPOLL Loop */
491 os_setup_epoll();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700492}
493
Jeff Dikec14b8492007-05-10 22:22:34 -0700494/*
495 * IRQ stack entry and exit:
496 *
497 * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
498 * and switch over to the IRQ stack after some preparation. We use
499 * sigaltstack to receive signals on a separate stack from the start.
500 * These two functions make sure the rest of the kernel won't be too
501 * upset by being on a different stack. The IRQ stack has a
502 * thread_info structure at the bottom so that current et al continue
503 * to work.
504 *
505 * to_irq_stack copies the current task's thread_info to the IRQ stack
506 * thread_info and sets the tasks's stack to point to the IRQ stack.
507 *
508 * from_irq_stack copies the thread_info struct back (flags may have
509 * been modified) and resets the task's stack pointer.
510 *
511 * Tricky bits -
512 *
513 * What happens when two signals race each other? UML doesn't block
514 * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
515 * could arrive while a previous one is still setting up the
516 * thread_info.
517 *
518 * There are three cases -
519 * The first interrupt on the stack - sets up the thread_info and
520 * handles the interrupt
521 * A nested interrupt interrupting the copying of the thread_info -
522 * can't handle the interrupt, as the stack is in an unknown state
523 * A nested interrupt not interrupting the copying of the
524 * thread_info - doesn't do any setup, just handles the interrupt
525 *
526 * The first job is to figure out whether we interrupted stack setup.
527 * This is done by xchging the signal mask with thread_info->pending.
528 * If the value that comes back is zero, then there is no setup in
529 * progress, and the interrupt can be handled. If the value is
530 * non-zero, then there is stack setup in progress. In order to have
531 * the interrupt handled, we leave our signal in the mask, and it will
532 * be handled by the upper handler after it has set up the stack.
533 *
534 * Next is to figure out whether we are the outer handler or a nested
535 * one. As part of setting up the stack, thread_info->real_thread is
536 * set to non-NULL (and is reset to NULL on exit). This is the
537 * nesting indicator. If it is non-NULL, then the stack is already
538 * set up and the handler can run.
539 */
540
541static unsigned long pending_mask;
542
Jeff Dike508a9272007-09-18 22:46:49 -0700543unsigned long to_irq_stack(unsigned long *mask_out)
Jeff Dikec14b8492007-05-10 22:22:34 -0700544{
545 struct thread_info *ti;
546 unsigned long mask, old;
547 int nested;
548
Jeff Dike508a9272007-09-18 22:46:49 -0700549 mask = xchg(&pending_mask, *mask_out);
Jeff Dikeba180fd2007-10-16 01:27:00 -0700550 if (mask != 0) {
551 /*
552 * If any interrupts come in at this point, we want to
Jeff Dikec14b8492007-05-10 22:22:34 -0700553 * make sure that their bits aren't lost by our
554 * putting our bit in. So, this loop accumulates bits
555 * until xchg returns the same value that we put in.
556 * When that happens, there were no new interrupts,
557 * and pending_mask contains a bit for each interrupt
558 * that came in.
559 */
Jeff Dike508a9272007-09-18 22:46:49 -0700560 old = *mask_out;
Jeff Dikec14b8492007-05-10 22:22:34 -0700561 do {
562 old |= mask;
563 mask = xchg(&pending_mask, old);
Jeff Dikeba180fd2007-10-16 01:27:00 -0700564 } while (mask != old);
Jeff Dikec14b8492007-05-10 22:22:34 -0700565 return 1;
566 }
567
568 ti = current_thread_info();
569 nested = (ti->real_thread != NULL);
Jeff Dikeba180fd2007-10-16 01:27:00 -0700570 if (!nested) {
Jeff Dikec14b8492007-05-10 22:22:34 -0700571 struct task_struct *task;
572 struct thread_info *tti;
573
574 task = cpu_tasks[ti->cpu].task;
575 tti = task_thread_info(task);
Jeff Dike508a9272007-09-18 22:46:49 -0700576
Jeff Dikec14b8492007-05-10 22:22:34 -0700577 *ti = *tti;
578 ti->real_thread = tti;
579 task->stack = ti;
580 }
581
582 mask = xchg(&pending_mask, 0);
583 *mask_out |= mask | nested;
584 return 0;
585}
586
587unsigned long from_irq_stack(int nested)
588{
589 struct thread_info *ti, *to;
590 unsigned long mask;
591
592 ti = current_thread_info();
593
594 pending_mask = 1;
595
596 to = ti->real_thread;
597 current->stack = to;
598 ti->real_thread = NULL;
599 *to = *ti;
600
601 mask = xchg(&pending_mask, 0);
602 return mask & ~1;
603}
604