Loading...
1/*
2 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
4 * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
5 * Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
6 */
7
8#include "linux/cpumask.h"
9#include "linux/hardirq.h"
10#include "linux/interrupt.h"
11#include "linux/kernel_stat.h"
12#include "linux/module.h"
13#include "linux/sched.h"
14#include "linux/seq_file.h"
15#include "linux/slab.h"
16#include "as-layout.h"
17#include "kern_util.h"
18#include "os.h"
19
20/*
21 * This list is accessed under irq_lock, except in sigio_handler,
22 * where it is safe from being modified. IRQ handlers won't change it -
23 * if an IRQ source has vanished, it will be freed by free_irqs just
24 * before returning from sigio_handler. That will process a separate
25 * list of irqs to free, with its own locking, coming back here to
26 * remove list elements, taking the irq_lock to do so.
27 */
28static struct irq_fd *active_fds = NULL;
29static struct irq_fd **last_irq_ptr = &active_fds;
30
31extern void free_irqs(void);
32
33void sigio_handler(int sig, struct uml_pt_regs *regs)
34{
35 struct irq_fd *irq_fd;
36 int n;
37
38 if (smp_sigio_handler())
39 return;
40
41 while (1) {
42 n = os_waiting_for_events(active_fds);
43 if (n <= 0) {
44 if (n == -EINTR)
45 continue;
46 else break;
47 }
48
49 for (irq_fd = active_fds; irq_fd != NULL;
50 irq_fd = irq_fd->next) {
51 if (irq_fd->current_events != 0) {
52 irq_fd->current_events = 0;
53 do_IRQ(irq_fd->irq, regs);
54 }
55 }
56 }
57
58 free_irqs();
59}
60
61static DEFINE_SPINLOCK(irq_lock);
62
63static int activate_fd(int irq, int fd, int type, void *dev_id)
64{
65 struct pollfd *tmp_pfd;
66 struct irq_fd *new_fd, *irq_fd;
67 unsigned long flags;
68 int events, err, n;
69
70 err = os_set_fd_async(fd);
71 if (err < 0)
72 goto out;
73
74 err = -ENOMEM;
75 new_fd = kmalloc(sizeof(struct irq_fd), GFP_KERNEL);
76 if (new_fd == NULL)
77 goto out;
78
79 if (type == IRQ_READ)
80 events = UM_POLLIN | UM_POLLPRI;
81 else events = UM_POLLOUT;
82 *new_fd = ((struct irq_fd) { .next = NULL,
83 .id = dev_id,
84 .fd = fd,
85 .type = type,
86 .irq = irq,
87 .events = events,
88 .current_events = 0 } );
89
90 err = -EBUSY;
91 spin_lock_irqsave(&irq_lock, flags);
92 for (irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next) {
93 if ((irq_fd->fd == fd) && (irq_fd->type == type)) {
94 printk(KERN_ERR "Registering fd %d twice\n", fd);
95 printk(KERN_ERR "Irqs : %d, %d\n", irq_fd->irq, irq);
96 printk(KERN_ERR "Ids : 0x%p, 0x%p\n", irq_fd->id,
97 dev_id);
98 goto out_unlock;
99 }
100 }
101
102 if (type == IRQ_WRITE)
103 fd = -1;
104
105 tmp_pfd = NULL;
106 n = 0;
107
108 while (1) {
109 n = os_create_pollfd(fd, events, tmp_pfd, n);
110 if (n == 0)
111 break;
112
113 /*
114 * n > 0
115 * It means we couldn't put new pollfd to current pollfds
116 * and tmp_fds is NULL or too small for new pollfds array.
117 * Needed size is equal to n as minimum.
118 *
119 * Here we have to drop the lock in order to call
120 * kmalloc, which might sleep.
121 * If something else came in and changed the pollfds array
122 * so we will not be able to put new pollfd struct to pollfds
123 * then we free the buffer tmp_fds and try again.
124 */
125 spin_unlock_irqrestore(&irq_lock, flags);
126 kfree(tmp_pfd);
127
128 tmp_pfd = kmalloc(n, GFP_KERNEL);
129 if (tmp_pfd == NULL)
130 goto out_kfree;
131
132 spin_lock_irqsave(&irq_lock, flags);
133 }
134
135 *last_irq_ptr = new_fd;
136 last_irq_ptr = &new_fd->next;
137
138 spin_unlock_irqrestore(&irq_lock, flags);
139
140 /*
141 * This calls activate_fd, so it has to be outside the critical
142 * section.
143 */
144 maybe_sigio_broken(fd, (type == IRQ_READ));
145
146 return 0;
147
148 out_unlock:
149 spin_unlock_irqrestore(&irq_lock, flags);
150 out_kfree:
151 kfree(new_fd);
152 out:
153 return err;
154}
155
156static void free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg)
157{
158 unsigned long flags;
159
160 spin_lock_irqsave(&irq_lock, flags);
161 os_free_irq_by_cb(test, arg, active_fds, &last_irq_ptr);
162 spin_unlock_irqrestore(&irq_lock, flags);
163}
164
165struct irq_and_dev {
166 int irq;
167 void *dev;
168};
169
170static int same_irq_and_dev(struct irq_fd *irq, void *d)
171{
172 struct irq_and_dev *data = d;
173
174 return ((irq->irq == data->irq) && (irq->id == data->dev));
175}
176
177static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
178{
179 struct irq_and_dev data = ((struct irq_and_dev) { .irq = irq,
180 .dev = dev });
181
182 free_irq_by_cb(same_irq_and_dev, &data);
183}
184
185static int same_fd(struct irq_fd *irq, void *fd)
186{
187 return (irq->fd == *((int *)fd));
188}
189
190void free_irq_by_fd(int fd)
191{
192 free_irq_by_cb(same_fd, &fd);
193}
194
195/* Must be called with irq_lock held */
196static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out)
197{
198 struct irq_fd *irq;
199 int i = 0;
200 int fdi;
201
202 for (irq = active_fds; irq != NULL; irq = irq->next) {
203 if ((irq->fd == fd) && (irq->irq == irqnum))
204 break;
205 i++;
206 }
207 if (irq == NULL) {
208 printk(KERN_ERR "find_irq_by_fd doesn't have descriptor %d\n",
209 fd);
210 goto out;
211 }
212 fdi = os_get_pollfd(i);
213 if ((fdi != -1) && (fdi != fd)) {
214 printk(KERN_ERR "find_irq_by_fd - mismatch between active_fds "
215 "and pollfds, fd %d vs %d, need %d\n", irq->fd,
216 fdi, fd);
217 irq = NULL;
218 goto out;
219 }
220 *index_out = i;
221 out:
222 return irq;
223}
224
225void reactivate_fd(int fd, int irqnum)
226{
227 struct irq_fd *irq;
228 unsigned long flags;
229 int i;
230
231 spin_lock_irqsave(&irq_lock, flags);
232 irq = find_irq_by_fd(fd, irqnum, &i);
233 if (irq == NULL) {
234 spin_unlock_irqrestore(&irq_lock, flags);
235 return;
236 }
237 os_set_pollfd(i, irq->fd);
238 spin_unlock_irqrestore(&irq_lock, flags);
239
240 add_sigio_fd(fd);
241}
242
243void deactivate_fd(int fd, int irqnum)
244{
245 struct irq_fd *irq;
246 unsigned long flags;
247 int i;
248
249 spin_lock_irqsave(&irq_lock, flags);
250 irq = find_irq_by_fd(fd, irqnum, &i);
251 if (irq == NULL) {
252 spin_unlock_irqrestore(&irq_lock, flags);
253 return;
254 }
255
256 os_set_pollfd(i, -1);
257 spin_unlock_irqrestore(&irq_lock, flags);
258
259 ignore_sigio_fd(fd);
260}
261EXPORT_SYMBOL(deactivate_fd);
262
263/*
264 * Called just before shutdown in order to provide a clean exec
265 * environment in case the system is rebooting. No locking because
266 * that would cause a pointless shutdown hang if something hadn't
267 * released the lock.
268 */
269int deactivate_all_fds(void)
270{
271 struct irq_fd *irq;
272 int err;
273
274 for (irq = active_fds; irq != NULL; irq = irq->next) {
275 err = os_clear_fd_async(irq->fd);
276 if (err)
277 return err;
278 }
279 /* If there is a signal already queued, after unblocking ignore it */
280 os_set_ioignore();
281
282 return 0;
283}
284
285/*
286 * do_IRQ handles all normal device IRQs (the special
287 * SMP cross-CPU interrupts have their own specific
288 * handlers).
289 */
290unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
291{
292 struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
293 irq_enter();
294 generic_handle_irq(irq);
295 irq_exit();
296 set_irq_regs(old_regs);
297 return 1;
298}
299
300void um_free_irq(unsigned int irq, void *dev)
301{
302 free_irq_by_irq_and_dev(irq, dev);
303 free_irq(irq, dev);
304}
305EXPORT_SYMBOL(um_free_irq);
306
307int um_request_irq(unsigned int irq, int fd, int type,
308 irq_handler_t handler,
309 unsigned long irqflags, const char * devname,
310 void *dev_id)
311{
312 int err;
313
314 if (fd != -1) {
315 err = activate_fd(irq, fd, type, dev_id);
316 if (err)
317 return err;
318 }
319
320 return request_irq(irq, handler, irqflags, devname, dev_id);
321}
322
323EXPORT_SYMBOL(um_request_irq);
324EXPORT_SYMBOL(reactivate_fd);
325
326/*
327 * irq_chip must define at least enable/disable and ack when
328 * the edge handler is used.
329 */
330static void dummy(struct irq_data *d)
331{
332}
333
334/* This is used for everything else than the timer. */
335static struct irq_chip normal_irq_type = {
336 .name = "SIGIO",
337 .irq_disable = dummy,
338 .irq_enable = dummy,
339 .irq_ack = dummy,
340};
341
342static struct irq_chip SIGVTALRM_irq_type = {
343 .name = "SIGVTALRM",
344 .irq_disable = dummy,
345 .irq_enable = dummy,
346 .irq_ack = dummy,
347};
348
349void __init init_IRQ(void)
350{
351 int i;
352
353 irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
354
355 for (i = 1; i < NR_IRQS; i++)
356 irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
357}
358
359/*
360 * IRQ stack entry and exit:
361 *
362 * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
363 * and switch over to the IRQ stack after some preparation. We use
364 * sigaltstack to receive signals on a separate stack from the start.
365 * These two functions make sure the rest of the kernel won't be too
366 * upset by being on a different stack. The IRQ stack has a
367 * thread_info structure at the bottom so that current et al continue
368 * to work.
369 *
370 * to_irq_stack copies the current task's thread_info to the IRQ stack
371 * thread_info and sets the tasks's stack to point to the IRQ stack.
372 *
373 * from_irq_stack copies the thread_info struct back (flags may have
374 * been modified) and resets the task's stack pointer.
375 *
376 * Tricky bits -
377 *
378 * What happens when two signals race each other? UML doesn't block
379 * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
380 * could arrive while a previous one is still setting up the
381 * thread_info.
382 *
383 * There are three cases -
384 * The first interrupt on the stack - sets up the thread_info and
385 * handles the interrupt
386 * A nested interrupt interrupting the copying of the thread_info -
387 * can't handle the interrupt, as the stack is in an unknown state
388 * A nested interrupt not interrupting the copying of the
389 * thread_info - doesn't do any setup, just handles the interrupt
390 *
391 * The first job is to figure out whether we interrupted stack setup.
392 * This is done by xchging the signal mask with thread_info->pending.
393 * If the value that comes back is zero, then there is no setup in
394 * progress, and the interrupt can be handled. If the value is
395 * non-zero, then there is stack setup in progress. In order to have
396 * the interrupt handled, we leave our signal in the mask, and it will
397 * be handled by the upper handler after it has set up the stack.
398 *
399 * Next is to figure out whether we are the outer handler or a nested
400 * one. As part of setting up the stack, thread_info->real_thread is
401 * set to non-NULL (and is reset to NULL on exit). This is the
402 * nesting indicator. If it is non-NULL, then the stack is already
403 * set up and the handler can run.
404 */
405
406static unsigned long pending_mask;
407
408unsigned long to_irq_stack(unsigned long *mask_out)
409{
410 struct thread_info *ti;
411 unsigned long mask, old;
412 int nested;
413
414 mask = xchg(&pending_mask, *mask_out);
415 if (mask != 0) {
416 /*
417 * If any interrupts come in at this point, we want to
418 * make sure that their bits aren't lost by our
419 * putting our bit in. So, this loop accumulates bits
420 * until xchg returns the same value that we put in.
421 * When that happens, there were no new interrupts,
422 * and pending_mask contains a bit for each interrupt
423 * that came in.
424 */
425 old = *mask_out;
426 do {
427 old |= mask;
428 mask = xchg(&pending_mask, old);
429 } while (mask != old);
430 return 1;
431 }
432
433 ti = current_thread_info();
434 nested = (ti->real_thread != NULL);
435 if (!nested) {
436 struct task_struct *task;
437 struct thread_info *tti;
438
439 task = cpu_tasks[ti->cpu].task;
440 tti = task_thread_info(task);
441
442 *ti = *tti;
443 ti->real_thread = tti;
444 task->stack = ti;
445 }
446
447 mask = xchg(&pending_mask, 0);
448 *mask_out |= mask | nested;
449 return 0;
450}
451
452unsigned long from_irq_stack(int nested)
453{
454 struct thread_info *ti, *to;
455 unsigned long mask;
456
457 ti = current_thread_info();
458
459 pending_mask = 1;
460
461 to = ti->real_thread;
462 current->stack = to;
463 ti->real_thread = NULL;
464 *to = *ti;
465
466 mask = xchg(&pending_mask, 0);
467 return mask & ~1;
468}
469
1/*
2 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
4 * Derived (i.e. mostly copied) from arch/i386/kernel/irq.c:
5 * Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
6 */
7
8#include "linux/cpumask.h"
9#include "linux/hardirq.h"
10#include "linux/interrupt.h"
11#include "linux/kernel_stat.h"
12#include "linux/module.h"
13#include "linux/sched.h"
14#include "linux/seq_file.h"
15#include "linux/slab.h"
16#include "as-layout.h"
17#include "kern_util.h"
18#include "os.h"
19
20/*
21 * This list is accessed under irq_lock, except in sigio_handler,
22 * where it is safe from being modified. IRQ handlers won't change it -
23 * if an IRQ source has vanished, it will be freed by free_irqs just
24 * before returning from sigio_handler. That will process a separate
25 * list of irqs to free, with its own locking, coming back here to
26 * remove list elements, taking the irq_lock to do so.
27 */
28static struct irq_fd *active_fds = NULL;
29static struct irq_fd **last_irq_ptr = &active_fds;
30
31extern void free_irqs(void);
32
33void sigio_handler(int sig, struct uml_pt_regs *regs)
34{
35 struct irq_fd *irq_fd;
36 int n;
37
38 if (smp_sigio_handler())
39 return;
40
41 while (1) {
42 n = os_waiting_for_events(active_fds);
43 if (n <= 0) {
44 if (n == -EINTR)
45 continue;
46 else break;
47 }
48
49 for (irq_fd = active_fds; irq_fd != NULL;
50 irq_fd = irq_fd->next) {
51 if (irq_fd->current_events != 0) {
52 irq_fd->current_events = 0;
53 do_IRQ(irq_fd->irq, regs);
54 }
55 }
56 }
57
58 free_irqs();
59}
60
61static DEFINE_SPINLOCK(irq_lock);
62
63static int activate_fd(int irq, int fd, int type, void *dev_id)
64{
65 struct pollfd *tmp_pfd;
66 struct irq_fd *new_fd, *irq_fd;
67 unsigned long flags;
68 int events, err, n;
69
70 err = os_set_fd_async(fd);
71 if (err < 0)
72 goto out;
73
74 err = -ENOMEM;
75 new_fd = kmalloc(sizeof(struct irq_fd), GFP_KERNEL);
76 if (new_fd == NULL)
77 goto out;
78
79 if (type == IRQ_READ)
80 events = UM_POLLIN | UM_POLLPRI;
81 else events = UM_POLLOUT;
82 *new_fd = ((struct irq_fd) { .next = NULL,
83 .id = dev_id,
84 .fd = fd,
85 .type = type,
86 .irq = irq,
87 .events = events,
88 .current_events = 0 } );
89
90 err = -EBUSY;
91 spin_lock_irqsave(&irq_lock, flags);
92 for (irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next) {
93 if ((irq_fd->fd == fd) && (irq_fd->type == type)) {
94 printk(KERN_ERR "Registering fd %d twice\n", fd);
95 printk(KERN_ERR "Irqs : %d, %d\n", irq_fd->irq, irq);
96 printk(KERN_ERR "Ids : 0x%p, 0x%p\n", irq_fd->id,
97 dev_id);
98 goto out_unlock;
99 }
100 }
101
102 if (type == IRQ_WRITE)
103 fd = -1;
104
105 tmp_pfd = NULL;
106 n = 0;
107
108 while (1) {
109 n = os_create_pollfd(fd, events, tmp_pfd, n);
110 if (n == 0)
111 break;
112
113 /*
114 * n > 0
115 * It means we couldn't put new pollfd to current pollfds
116 * and tmp_fds is NULL or too small for new pollfds array.
117 * Needed size is equal to n as minimum.
118 *
119 * Here we have to drop the lock in order to call
120 * kmalloc, which might sleep.
121 * If something else came in and changed the pollfds array
122 * so we will not be able to put new pollfd struct to pollfds
123 * then we free the buffer tmp_fds and try again.
124 */
125 spin_unlock_irqrestore(&irq_lock, flags);
126 kfree(tmp_pfd);
127
128 tmp_pfd = kmalloc(n, GFP_KERNEL);
129 if (tmp_pfd == NULL)
130 goto out_kfree;
131
132 spin_lock_irqsave(&irq_lock, flags);
133 }
134
135 *last_irq_ptr = new_fd;
136 last_irq_ptr = &new_fd->next;
137
138 spin_unlock_irqrestore(&irq_lock, flags);
139
140 /*
141 * This calls activate_fd, so it has to be outside the critical
142 * section.
143 */
144 maybe_sigio_broken(fd, (type == IRQ_READ));
145
146 return 0;
147
148 out_unlock:
149 spin_unlock_irqrestore(&irq_lock, flags);
150 out_kfree:
151 kfree(new_fd);
152 out:
153 return err;
154}
155
156static void free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg)
157{
158 unsigned long flags;
159
160 spin_lock_irqsave(&irq_lock, flags);
161 os_free_irq_by_cb(test, arg, active_fds, &last_irq_ptr);
162 spin_unlock_irqrestore(&irq_lock, flags);
163}
164
165struct irq_and_dev {
166 int irq;
167 void *dev;
168};
169
170static int same_irq_and_dev(struct irq_fd *irq, void *d)
171{
172 struct irq_and_dev *data = d;
173
174 return ((irq->irq == data->irq) && (irq->id == data->dev));
175}
176
177static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
178{
179 struct irq_and_dev data = ((struct irq_and_dev) { .irq = irq,
180 .dev = dev });
181
182 free_irq_by_cb(same_irq_and_dev, &data);
183}
184
185static int same_fd(struct irq_fd *irq, void *fd)
186{
187 return (irq->fd == *((int *)fd));
188}
189
190void free_irq_by_fd(int fd)
191{
192 free_irq_by_cb(same_fd, &fd);
193}
194
195/* Must be called with irq_lock held */
196static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out)
197{
198 struct irq_fd *irq;
199 int i = 0;
200 int fdi;
201
202 for (irq = active_fds; irq != NULL; irq = irq->next) {
203 if ((irq->fd == fd) && (irq->irq == irqnum))
204 break;
205 i++;
206 }
207 if (irq == NULL) {
208 printk(KERN_ERR "find_irq_by_fd doesn't have descriptor %d\n",
209 fd);
210 goto out;
211 }
212 fdi = os_get_pollfd(i);
213 if ((fdi != -1) && (fdi != fd)) {
214 printk(KERN_ERR "find_irq_by_fd - mismatch between active_fds "
215 "and pollfds, fd %d vs %d, need %d\n", irq->fd,
216 fdi, fd);
217 irq = NULL;
218 goto out;
219 }
220 *index_out = i;
221 out:
222 return irq;
223}
224
225void reactivate_fd(int fd, int irqnum)
226{
227 struct irq_fd *irq;
228 unsigned long flags;
229 int i;
230
231 spin_lock_irqsave(&irq_lock, flags);
232 irq = find_irq_by_fd(fd, irqnum, &i);
233 if (irq == NULL) {
234 spin_unlock_irqrestore(&irq_lock, flags);
235 return;
236 }
237 os_set_pollfd(i, irq->fd);
238 spin_unlock_irqrestore(&irq_lock, flags);
239
240 add_sigio_fd(fd);
241}
242
243void deactivate_fd(int fd, int irqnum)
244{
245 struct irq_fd *irq;
246 unsigned long flags;
247 int i;
248
249 spin_lock_irqsave(&irq_lock, flags);
250 irq = find_irq_by_fd(fd, irqnum, &i);
251 if (irq == NULL) {
252 spin_unlock_irqrestore(&irq_lock, flags);
253 return;
254 }
255
256 os_set_pollfd(i, -1);
257 spin_unlock_irqrestore(&irq_lock, flags);
258
259 ignore_sigio_fd(fd);
260}
261
262/*
263 * Called just before shutdown in order to provide a clean exec
264 * environment in case the system is rebooting. No locking because
265 * that would cause a pointless shutdown hang if something hadn't
266 * released the lock.
267 */
268int deactivate_all_fds(void)
269{
270 struct irq_fd *irq;
271 int err;
272
273 for (irq = active_fds; irq != NULL; irq = irq->next) {
274 err = os_clear_fd_async(irq->fd);
275 if (err)
276 return err;
277 }
278 /* If there is a signal already queued, after unblocking ignore it */
279 os_set_ioignore();
280
281 return 0;
282}
283
284/*
285 * do_IRQ handles all normal device IRQs (the special
286 * SMP cross-CPU interrupts have their own specific
287 * handlers).
288 */
289unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
290{
291 struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
292 irq_enter();
293 generic_handle_irq(irq);
294 irq_exit();
295 set_irq_regs(old_regs);
296 return 1;
297}
298
299int um_request_irq(unsigned int irq, int fd, int type,
300 irq_handler_t handler,
301 unsigned long irqflags, const char * devname,
302 void *dev_id)
303{
304 int err;
305
306 if (fd != -1) {
307 err = activate_fd(irq, fd, type, dev_id);
308 if (err)
309 return err;
310 }
311
312 return request_irq(irq, handler, irqflags, devname, dev_id);
313}
314
315EXPORT_SYMBOL(um_request_irq);
316EXPORT_SYMBOL(reactivate_fd);
317
318/*
319 * irq_chip must define at least enable/disable and ack when
320 * the edge handler is used.
321 */
322static void dummy(struct irq_data *d)
323{
324}
325
326/* This is used for everything else than the timer. */
327static struct irq_chip normal_irq_type = {
328 .name = "SIGIO",
329 .release = free_irq_by_irq_and_dev,
330 .irq_disable = dummy,
331 .irq_enable = dummy,
332 .irq_ack = dummy,
333};
334
335static struct irq_chip SIGVTALRM_irq_type = {
336 .name = "SIGVTALRM",
337 .release = free_irq_by_irq_and_dev,
338 .irq_disable = dummy,
339 .irq_enable = dummy,
340 .irq_ack = dummy,
341};
342
343void __init init_IRQ(void)
344{
345 int i;
346
347 irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
348
349 for (i = 1; i < NR_IRQS; i++)
350 irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
351}
352
353/*
354 * IRQ stack entry and exit:
355 *
356 * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
357 * and switch over to the IRQ stack after some preparation. We use
358 * sigaltstack to receive signals on a separate stack from the start.
359 * These two functions make sure the rest of the kernel won't be too
360 * upset by being on a different stack. The IRQ stack has a
361 * thread_info structure at the bottom so that current et al continue
362 * to work.
363 *
364 * to_irq_stack copies the current task's thread_info to the IRQ stack
365 * thread_info and sets the tasks's stack to point to the IRQ stack.
366 *
367 * from_irq_stack copies the thread_info struct back (flags may have
368 * been modified) and resets the task's stack pointer.
369 *
370 * Tricky bits -
371 *
372 * What happens when two signals race each other? UML doesn't block
373 * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
374 * could arrive while a previous one is still setting up the
375 * thread_info.
376 *
377 * There are three cases -
378 * The first interrupt on the stack - sets up the thread_info and
379 * handles the interrupt
380 * A nested interrupt interrupting the copying of the thread_info -
381 * can't handle the interrupt, as the stack is in an unknown state
382 * A nested interrupt not interrupting the copying of the
383 * thread_info - doesn't do any setup, just handles the interrupt
384 *
385 * The first job is to figure out whether we interrupted stack setup.
386 * This is done by xchging the signal mask with thread_info->pending.
387 * If the value that comes back is zero, then there is no setup in
388 * progress, and the interrupt can be handled. If the value is
389 * non-zero, then there is stack setup in progress. In order to have
390 * the interrupt handled, we leave our signal in the mask, and it will
391 * be handled by the upper handler after it has set up the stack.
392 *
393 * Next is to figure out whether we are the outer handler or a nested
394 * one. As part of setting up the stack, thread_info->real_thread is
395 * set to non-NULL (and is reset to NULL on exit). This is the
396 * nesting indicator. If it is non-NULL, then the stack is already
397 * set up and the handler can run.
398 */
399
400static unsigned long pending_mask;
401
402unsigned long to_irq_stack(unsigned long *mask_out)
403{
404 struct thread_info *ti;
405 unsigned long mask, old;
406 int nested;
407
408 mask = xchg(&pending_mask, *mask_out);
409 if (mask != 0) {
410 /*
411 * If any interrupts come in at this point, we want to
412 * make sure that their bits aren't lost by our
413 * putting our bit in. So, this loop accumulates bits
414 * until xchg returns the same value that we put in.
415 * When that happens, there were no new interrupts,
416 * and pending_mask contains a bit for each interrupt
417 * that came in.
418 */
419 old = *mask_out;
420 do {
421 old |= mask;
422 mask = xchg(&pending_mask, old);
423 } while (mask != old);
424 return 1;
425 }
426
427 ti = current_thread_info();
428 nested = (ti->real_thread != NULL);
429 if (!nested) {
430 struct task_struct *task;
431 struct thread_info *tti;
432
433 task = cpu_tasks[ti->cpu].task;
434 tti = task_thread_info(task);
435
436 *ti = *tti;
437 ti->real_thread = tti;
438 task->stack = ti;
439 }
440
441 mask = xchg(&pending_mask, 0);
442 *mask_out |= mask | nested;
443 return 0;
444}
445
446unsigned long from_irq_stack(int nested)
447{
448 struct thread_info *ti, *to;
449 unsigned long mask;
450
451 ti = current_thread_info();
452
453 pending_mask = 1;
454
455 to = ti->real_thread;
456 current->stack = to;
457 ti->real_thread = NULL;
458 *to = *ti;
459
460 mask = xchg(&pending_mask, 0);
461 return mask & ~1;
462}
463