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Linux/arch/um/kernel/irq.c

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  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  */
 28 static struct irq_fd *active_fds = NULL;
 29 static struct irq_fd **last_irq_ptr = &active_fds;
 30 
 31 extern void free_irqs(void);
 32 
 33 void sigio_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
 34 {
 35         struct irq_fd *irq_fd;
 36         int n;
 37 
 38         while (1) {
 39                 n = os_waiting_for_events(active_fds);
 40                 if (n <= 0) {
 41                         if (n == -EINTR)
 42                                 continue;
 43                         else break;
 44                 }
 45 
 46                 for (irq_fd = active_fds; irq_fd != NULL;
 47                      irq_fd = irq_fd->next) {
 48                         if (irq_fd->current_events != 0) {
 49                                 irq_fd->current_events = 0;
 50                                 do_IRQ(irq_fd->irq, regs);
 51                         }
 52                 }
 53         }
 54 
 55         free_irqs();
 56 }
 57 
 58 static DEFINE_SPINLOCK(irq_lock);
 59 
 60 static int activate_fd(int irq, int fd, int type, void *dev_id)
 61 {
 62         struct pollfd *tmp_pfd;
 63         struct irq_fd *new_fd, *irq_fd;
 64         unsigned long flags;
 65         int events, err, n;
 66 
 67         err = os_set_fd_async(fd);
 68         if (err < 0)
 69                 goto out;
 70 
 71         err = -ENOMEM;
 72         new_fd = kmalloc(sizeof(struct irq_fd), GFP_KERNEL);
 73         if (new_fd == NULL)
 74                 goto out;
 75 
 76         if (type == IRQ_READ)
 77                 events = UM_POLLIN | UM_POLLPRI;
 78         else events = UM_POLLOUT;
 79         *new_fd = ((struct irq_fd) { .next              = NULL,
 80                                      .id                = dev_id,
 81                                      .fd                = fd,
 82                                      .type              = type,
 83                                      .irq               = irq,
 84                                      .events            = events,
 85                                      .current_events    = 0 } );
 86 
 87         err = -EBUSY;
 88         spin_lock_irqsave(&irq_lock, flags);
 89         for (irq_fd = active_fds; irq_fd != NULL; irq_fd = irq_fd->next) {
 90                 if ((irq_fd->fd == fd) && (irq_fd->type == type)) {
 91                         printk(KERN_ERR "Registering fd %d twice\n", fd);
 92                         printk(KERN_ERR "Irqs : %d, %d\n", irq_fd->irq, irq);
 93                         printk(KERN_ERR "Ids : 0x%p, 0x%p\n", irq_fd->id,
 94                                dev_id);
 95                         goto out_unlock;
 96                 }
 97         }
 98 
 99         if (type == IRQ_WRITE)
100                 fd = -1;
101 
102         tmp_pfd = NULL;
103         n = 0;
104 
105         while (1) {
106                 n = os_create_pollfd(fd, events, tmp_pfd, n);
107                 if (n == 0)
108                         break;
109 
110                 /*
111                  * n > 0
112                  * It means we couldn't put new pollfd to current pollfds
113                  * and tmp_fds is NULL or too small for new pollfds array.
114                  * Needed size is equal to n as minimum.
115                  *
116                  * Here we have to drop the lock in order to call
117                  * kmalloc, which might sleep.
118                  * If something else came in and changed the pollfds array
119                  * so we will not be able to put new pollfd struct to pollfds
120                  * then we free the buffer tmp_fds and try again.
121                  */
122                 spin_unlock_irqrestore(&irq_lock, flags);
123                 kfree(tmp_pfd);
124 
125                 tmp_pfd = kmalloc(n, GFP_KERNEL);
126                 if (tmp_pfd == NULL)
127                         goto out_kfree;
128 
129                 spin_lock_irqsave(&irq_lock, flags);
130         }
131 
132         *last_irq_ptr = new_fd;
133         last_irq_ptr = &new_fd->next;
134 
135         spin_unlock_irqrestore(&irq_lock, flags);
136 
137         /*
138          * This calls activate_fd, so it has to be outside the critical
139          * section.
140          */
141         maybe_sigio_broken(fd, (type == IRQ_READ));
142 
143         return 0;
144 
145  out_unlock:
146         spin_unlock_irqrestore(&irq_lock, flags);
147  out_kfree:
148         kfree(new_fd);
149  out:
150         return err;
151 }
152 
153 static void free_irq_by_cb(int (*test)(struct irq_fd *, void *), void *arg)
154 {
155         unsigned long flags;
156 
157         spin_lock_irqsave(&irq_lock, flags);
158         os_free_irq_by_cb(test, arg, active_fds, &last_irq_ptr);
159         spin_unlock_irqrestore(&irq_lock, flags);
160 }
161 
162 struct irq_and_dev {
163         int irq;
164         void *dev;
165 };
166 
167 static int same_irq_and_dev(struct irq_fd *irq, void *d)
168 {
169         struct irq_and_dev *data = d;
170 
171         return ((irq->irq == data->irq) && (irq->id == data->dev));
172 }
173 
174 static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
175 {
176         struct irq_and_dev data = ((struct irq_and_dev) { .irq  = irq,
177                                                           .dev  = dev });
178 
179         free_irq_by_cb(same_irq_and_dev, &data);
180 }
181 
182 static int same_fd(struct irq_fd *irq, void *fd)
183 {
184         return (irq->fd == *((int *)fd));
185 }
186 
187 void free_irq_by_fd(int fd)
188 {
189         free_irq_by_cb(same_fd, &fd);
190 }
191 
192 /* Must be called with irq_lock held */
193 static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out)
194 {
195         struct irq_fd *irq;
196         int i = 0;
197         int fdi;
198 
199         for (irq = active_fds; irq != NULL; irq = irq->next) {
200                 if ((irq->fd == fd) && (irq->irq == irqnum))
201                         break;
202                 i++;
203         }
204         if (irq == NULL) {
205                 printk(KERN_ERR "find_irq_by_fd doesn't have descriptor %d\n",
206                        fd);
207                 goto out;
208         }
209         fdi = os_get_pollfd(i);
210         if ((fdi != -1) && (fdi != fd)) {
211                 printk(KERN_ERR "find_irq_by_fd - mismatch between active_fds "
212                        "and pollfds, fd %d vs %d, need %d\n", irq->fd,
213                        fdi, fd);
214                 irq = NULL;
215                 goto out;
216         }
217         *index_out = i;
218  out:
219         return irq;
220 }
221 
222 void reactivate_fd(int fd, int irqnum)
223 {
224         struct irq_fd *irq;
225         unsigned long flags;
226         int i;
227 
228         spin_lock_irqsave(&irq_lock, flags);
229         irq = find_irq_by_fd(fd, irqnum, &i);
230         if (irq == NULL) {
231                 spin_unlock_irqrestore(&irq_lock, flags);
232                 return;
233         }
234         os_set_pollfd(i, irq->fd);
235         spin_unlock_irqrestore(&irq_lock, flags);
236 
237         add_sigio_fd(fd);
238 }
239 
240 void deactivate_fd(int fd, int irqnum)
241 {
242         struct irq_fd *irq;
243         unsigned long flags;
244         int i;
245 
246         spin_lock_irqsave(&irq_lock, flags);
247         irq = find_irq_by_fd(fd, irqnum, &i);
248         if (irq == NULL) {
249                 spin_unlock_irqrestore(&irq_lock, flags);
250                 return;
251         }
252 
253         os_set_pollfd(i, -1);
254         spin_unlock_irqrestore(&irq_lock, flags);
255 
256         ignore_sigio_fd(fd);
257 }
258 EXPORT_SYMBOL(deactivate_fd);
259 
260 /*
261  * Called just before shutdown in order to provide a clean exec
262  * environment in case the system is rebooting.  No locking because
263  * that would cause a pointless shutdown hang if something hadn't
264  * released the lock.
265  */
266 int deactivate_all_fds(void)
267 {
268         struct irq_fd *irq;
269         int err;
270 
271         for (irq = active_fds; irq != NULL; irq = irq->next) {
272                 err = os_clear_fd_async(irq->fd);
273                 if (err)
274                         return err;
275         }
276         /* If there is a signal already queued, after unblocking ignore it */
277         os_set_ioignore();
278 
279         return 0;
280 }
281 
282 /*
283  * do_IRQ handles all normal device IRQs (the special
284  * SMP cross-CPU interrupts have their own specific
285  * handlers).
286  */
287 unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
288 {
289         struct pt_regs *old_regs = set_irq_regs((struct pt_regs *)regs);
290         irq_enter();
291         generic_handle_irq(irq);
292         irq_exit();
293         set_irq_regs(old_regs);
294         return 1;
295 }
296 
297 void um_free_irq(unsigned int irq, void *dev)
298 {
299         free_irq_by_irq_and_dev(irq, dev);
300         free_irq(irq, dev);
301 }
302 EXPORT_SYMBOL(um_free_irq);
303 
304 int um_request_irq(unsigned int irq, int fd, int type,
305                    irq_handler_t handler,
306                    unsigned long irqflags, const char * devname,
307                    void *dev_id)
308 {
309         int err;
310 
311         if (fd != -1) {
312                 err = activate_fd(irq, fd, type, dev_id);
313                 if (err)
314                         return err;
315         }
316 
317         return request_irq(irq, handler, irqflags, devname, dev_id);
318 }
319 
320 EXPORT_SYMBOL(um_request_irq);
321 EXPORT_SYMBOL(reactivate_fd);
322 
323 /*
324  * irq_chip must define at least enable/disable and ack when
325  * the edge handler is used.
326  */
327 static void dummy(struct irq_data *d)
328 {
329 }
330 
331 /* This is used for everything else than the timer. */
332 static struct irq_chip normal_irq_type = {
333         .name = "SIGIO",
334         .irq_disable = dummy,
335         .irq_enable = dummy,
336         .irq_ack = dummy,
337         .irq_mask = dummy,
338         .irq_unmask = dummy,
339 };
340 
341 static struct irq_chip SIGVTALRM_irq_type = {
342         .name = "SIGVTALRM",
343         .irq_disable = dummy,
344         .irq_enable = dummy,
345         .irq_ack = dummy,
346         .irq_mask = dummy,
347         .irq_unmask = dummy,
348 };
349 
350 void __init init_IRQ(void)
351 {
352         int i;
353 
354         irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
355 
356         for (i = 1; i < NR_IRQS; i++)
357                 irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
358 }
359 
360 /*
361  * IRQ stack entry and exit:
362  *
363  * Unlike i386, UML doesn't receive IRQs on the normal kernel stack
364  * and switch over to the IRQ stack after some preparation.  We use
365  * sigaltstack to receive signals on a separate stack from the start.
366  * These two functions make sure the rest of the kernel won't be too
367  * upset by being on a different stack.  The IRQ stack has a
368  * thread_info structure at the bottom so that current et al continue
369  * to work.
370  *
371  * to_irq_stack copies the current task's thread_info to the IRQ stack
372  * thread_info and sets the tasks's stack to point to the IRQ stack.
373  *
374  * from_irq_stack copies the thread_info struct back (flags may have
375  * been modified) and resets the task's stack pointer.
376  *
377  * Tricky bits -
378  *
379  * What happens when two signals race each other?  UML doesn't block
380  * signals with sigprocmask, SA_DEFER, or sa_mask, so a second signal
381  * could arrive while a previous one is still setting up the
382  * thread_info.
383  *
384  * There are three cases -
385  *     The first interrupt on the stack - sets up the thread_info and
386  * handles the interrupt
387  *     A nested interrupt interrupting the copying of the thread_info -
388  * can't handle the interrupt, as the stack is in an unknown state
389  *     A nested interrupt not interrupting the copying of the
390  * thread_info - doesn't do any setup, just handles the interrupt
391  *
392  * The first job is to figure out whether we interrupted stack setup.
393  * This is done by xchging the signal mask with thread_info->pending.
394  * If the value that comes back is zero, then there is no setup in
395  * progress, and the interrupt can be handled.  If the value is
396  * non-zero, then there is stack setup in progress.  In order to have
397  * the interrupt handled, we leave our signal in the mask, and it will
398  * be handled by the upper handler after it has set up the stack.
399  *
400  * Next is to figure out whether we are the outer handler or a nested
401  * one.  As part of setting up the stack, thread_info->real_thread is
402  * set to non-NULL (and is reset to NULL on exit).  This is the
403  * nesting indicator.  If it is non-NULL, then the stack is already
404  * set up and the handler can run.
405  */
406 
407 static unsigned long pending_mask;
408 
409 unsigned long to_irq_stack(unsigned long *mask_out)
410 {
411         struct thread_info *ti;
412         unsigned long mask, old;
413         int nested;
414 
415         mask = xchg(&pending_mask, *mask_out);
416         if (mask != 0) {
417                 /*
418                  * If any interrupts come in at this point, we want to
419                  * make sure that their bits aren't lost by our
420                  * putting our bit in.  So, this loop accumulates bits
421                  * until xchg returns the same value that we put in.
422                  * When that happens, there were no new interrupts,
423                  * and pending_mask contains a bit for each interrupt
424                  * that came in.
425                  */
426                 old = *mask_out;
427                 do {
428                         old |= mask;
429                         mask = xchg(&pending_mask, old);
430                 } while (mask != old);
431                 return 1;
432         }
433 
434         ti = current_thread_info();
435         nested = (ti->real_thread != NULL);
436         if (!nested) {
437                 struct task_struct *task;
438                 struct thread_info *tti;
439 
440                 task = cpu_tasks[ti->cpu].task;
441                 tti = task_thread_info(task);
442 
443                 *ti = *tti;
444                 ti->real_thread = tti;
445                 task->stack = ti;
446         }
447 
448         mask = xchg(&pending_mask, 0);
449         *mask_out |= mask | nested;
450         return 0;
451 }
452 
453 unsigned long from_irq_stack(int nested)
454 {
455         struct thread_info *ti, *to;
456         unsigned long mask;
457 
458         ti = current_thread_info();
459 
460         pending_mask = 1;
461 
462         to = ti->real_thread;
463         current->stack = to;
464         ti->real_thread = NULL;
465         *to = *ti;
466 
467         mask = xchg(&pending_mask, 0);
468         return mask & ~1;
469 }
470 
471 

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