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kernel - Fix excessive call stack depth on stuck interrupt
[dragonfly.git] / sys / kern / sys_process.c
blobf8d03a490a0a40179b70140ce7dac43f9b9ab7b6
1 /*
2 * Copyright (c) 1994, Sean Eric Fagan
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by Sean Eric Fagan.
16 * 4. The name of the author may not be used to endorse or promote products
17 * derived from this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 *
31 * $FreeBSD: src/sys/kern/sys_process.c,v 1.51.2.6 2003/01/08 03:06:45 kan Exp $
32 * $DragonFly: src/sys/kern/sys_process.c,v 1.30 2007/02/19 01:14:23 corecode Exp $
33 */
34
35 #include <sys/param.h>
36 #include <sys/systm.h>
37 #include <sys/sysproto.h>
38 #include <sys/proc.h>
39 #include <sys/priv.h>
40 #include <sys/vnode.h>
41 #include <sys/ptrace.h>
42 #include <sys/reg.h>
43 #include <sys/lock.h>
44
45 #include <vm/vm.h>
46 #include <vm/pmap.h>
47 #include <vm/vm_map.h>
48 #include <vm/vm_page.h>
49
50 #include <sys/user.h>
51 #include <vfs/procfs/procfs.h>
52
53 #include <sys/thread2.h>
54 #include <sys/spinlock2.h>
55
56 /* use the equivalent procfs code */
57 #if 0
58 static int
59 pread (struct proc *procp, unsigned int addr, unsigned int *retval) {
60 int rv;
61 vm_map_t map, tmap;
62 vm_object_t object;
63 vm_offset_t kva = 0;
64 int page_offset; /* offset into page */
65 vm_offset_t pageno; /* page number */
66 vm_map_entry_t out_entry;
67 vm_prot_t out_prot;
68 boolean_t wired;
69 vm_pindex_t pindex;
70
71 /* Map page into kernel space */
72
73 map = &procp->p_vmspace->vm_map;
74
75 page_offset = addr - trunc_page(addr);
76 pageno = trunc_page(addr);
77
78 tmap = map;
79 rv = vm_map_lookup(&tmap, pageno, VM_PROT_READ, &out_entry,
80 &object, &pindex, &out_prot, &wired);
81
82 if (rv != KERN_SUCCESS)
83 return EINVAL;
84
85 vm_map_lookup_done (tmap, out_entry, 0);
86
87 /* Find space in kernel_map for the page we're interested in */
88 rv = vm_map_find (&kernel_map, object, NULL,
89 IDX_TO_OFF(pindex), &kva, PAGE_SIZE,
90 PAGE_SIZE, FALSE,
91 VM_MAPTYPE_NORMAL, VM_SUBSYS_PROC,
92 VM_PROT_ALL, VM_PROT_ALL, 0);
93
94 if (!rv) {
95 vm_object_reference XXX (object);
96
97 rv = vm_map_wire (&kernel_map, kva, kva + PAGE_SIZE, 0);
98 if (!rv) {
99 *retval = 0;
100 bcopy ((caddr_t)kva + page_offset,
101 retval, sizeof *retval);
102 }
103 vm_map_remove (&kernel_map, kva, kva + PAGE_SIZE);
104 }
105
106 return rv;
107 }
108
109 static int
110 pwrite (struct proc *procp, unsigned int addr, unsigned int datum) {
111 int rv;
112 vm_map_t map, tmap;
113 vm_object_t object;
114 vm_offset_t kva = 0;
115 int page_offset; /* offset into page */
116 vm_offset_t pageno; /* page number */
117 vm_map_entry_t out_entry;
118 vm_prot_t out_prot;
119 boolean_t wired;
120 vm_pindex_t pindex;
121 boolean_t fix_prot = 0;
122
123 /* Map page into kernel space */
124
125 map = &procp->p_vmspace->vm_map;
126
127 page_offset = addr - trunc_page(addr);
128 pageno = trunc_page(addr);
129
130 /*
131 * Check the permissions for the area we're interested in.
132 */
133
134 if (vm_map_check_protection (map, pageno, pageno + PAGE_SIZE,
135 VM_PROT_WRITE, FALSE) == FALSE) {
136 /*
137 * If the page was not writable, we make it so.
138 * XXX It is possible a page may *not* be read/executable,
139 * if a process changes that!
140 */
141 fix_prot = 1;
142 /* The page isn't writable, so let's try making it so... */
143 if ((rv = vm_map_protect (map, pageno, pageno + PAGE_SIZE,
144 VM_PROT_ALL, 0)) != KERN_SUCCESS)
145 return EFAULT; /* I guess... */
146 }
147
148 /*
149 * Now we need to get the page. out_entry, out_prot, wired, and
150 * single_use aren't used. One would think the vm code would be
151 * a *bit* nicer... We use tmap because vm_map_lookup() can
152 * change the map argument.
153 */
154
155 tmap = map;
156 rv = vm_map_lookup(&tmap, pageno, VM_PROT_WRITE, &out_entry,
157 &object, &pindex, &out_prot, &wired);
158 if (rv != KERN_SUCCESS)
159 return EINVAL;
160
161 /*
162 * Okay, we've got the page. Let's release tmap.
163 */
164 vm_map_lookup_done (tmap, out_entry, 0);
165
166 /*
167 * Fault the page in...
168 */
169 rv = vm_fault(map, pageno, VM_PROT_WRITE|VM_PROT_READ, FALSE);
170 if (rv != KERN_SUCCESS)
171 return EFAULT;
172
173 /* Find space in kernel_map for the page we're interested in */
174 rv = vm_map_find (&kernel_map, object, NULL,
175 IDX_TO_OFF(pindex), &kva, PAGE_SIZE,
176 PAGE_SIZE, FALSE,
177 VM_MAPTYPE_NORMAL, VM_SUBSYS_PROC,
178 VM_PROT_ALL, VM_PROT_ALL, 0);
179 if (!rv) {
180 vm_object_reference XXX (object);
181
182 rv = vm_map_wire (&kernel_map, kva, kva + PAGE_SIZE, 0);
183 if (!rv) {
184 bcopy (&datum, (caddr_t)kva + page_offset, sizeof datum);
185 }
186 vm_map_remove (&kernel_map, kva, kva + PAGE_SIZE);
187 }
188
189 if (fix_prot)
190 vm_map_protect (map, pageno, pageno + PAGE_SIZE,
191 VM_PROT_READ|VM_PROT_EXECUTE, 0);
192 return rv;
193 }
194 #endif
195
196 /*
197 * Process debugging system call.
198 *
199 * MPALMOSTSAFE
200 */
201 int
202 sys_ptrace(struct ptrace_args *uap)
203 {
204 struct proc *p = curproc;
205
206 /*
207 * XXX this obfuscation is to reduce stack usage, but the register
208 * structs may be too large to put on the stack anyway.
209 */
210 union {
211 struct ptrace_io_desc piod;
212 struct dbreg dbreg;
213 struct fpreg fpreg;
214 struct reg reg;
215 } r;
216 void *addr;
217 int error = 0;
218
219 addr = &r;
220 switch (uap->req) {
221 case PT_GETREGS:
222 case PT_GETFPREGS:
223 #ifdef PT_GETDBREGS
224 case PT_GETDBREGS:
225 #endif
226 break;
227 case PT_SETREGS:
228 error = copyin(uap->addr, &r.reg, sizeof r.reg);
229 break;
230 case PT_SETFPREGS:
231 error = copyin(uap->addr, &r.fpreg, sizeof r.fpreg);
232 break;
233 #ifdef PT_SETDBREGS
234 case PT_SETDBREGS:
235 error = copyin(uap->addr, &r.dbreg, sizeof r.dbreg);
236 break;
237 #endif
238 case PT_IO:
239 error = copyin(uap->addr, &r.piod, sizeof r.piod);
240 break;
241 default:
242 addr = uap->addr;
243 }
244 if (error)
245 return (error);
246
247 error = kern_ptrace(p, uap->req, uap->pid, addr, uap->data,
248 &uap->sysmsg_result);
249 if (error)
250 return (error);
251
252 switch (uap->req) {
253 case PT_IO:
254 (void)copyout(&r.piod, uap->addr, sizeof r.piod);
255 break;
256 case PT_GETREGS:
257 error = copyout(&r.reg, uap->addr, sizeof r.reg);
258 break;
259 case PT_GETFPREGS:
260 error = copyout(&r.fpreg, uap->addr, sizeof r.fpreg);
261 break;
262 #ifdef PT_GETDBREGS
263 case PT_GETDBREGS:
264 error = copyout(&r.dbreg, uap->addr, sizeof r.dbreg);
265 break;
266 #endif
267 }
268
269 return (error);
270 }
271
272 int
273 kern_ptrace(struct proc *curp, int req, pid_t pid, void *addr,
274 int data, int *res)
275 {
276 struct proc *p, *pp;
277 struct lwp *lp;
278 struct iovec iov;
279 struct uio uio;
280 struct ptrace_io_desc *piod;
281 int error = 0;
282 int write, tmp;
283 int t;
284
285 write = 0;
286 if (req == PT_TRACE_ME) {
287 p = curp;
288 PHOLD(p);
289 } else {
290 if ((p = pfind(pid)) == NULL)
291 return ESRCH;
292 }
293 if (!PRISON_CHECK(curp->p_ucred, p->p_ucred)) {
294 PRELE(p);
295 return (ESRCH);
296 }
297 if (p->p_flags & P_SYSTEM) {
298 PRELE(p);
299 return EINVAL;
300 }
301
302 lwkt_gettoken(&p->p_token);
303 /* Can't trace a process that's currently exec'ing. */
304 if ((p->p_flags & P_INEXEC) != 0) {
305 lwkt_reltoken(&p->p_token);
306 PRELE(p);
307 return EAGAIN;
308 }
309
310 /*
311 * Permissions check
312 */
313 switch (req) {
314 case PT_TRACE_ME:
315 /* Always legal. */
316 break;
317
318 case PT_ATTACH:
319 /* Self */
320 if (p->p_pid == curp->p_pid) {
321 lwkt_reltoken(&p->p_token);
322 PRELE(p);
323 return EINVAL;
324 }
325
326 /* Already traced */
327 if (p->p_flags & P_TRACED) {
328 lwkt_reltoken(&p->p_token);
329 PRELE(p);
330 return EBUSY;
331 }
332
333 if (curp->p_flags & P_TRACED)
334 for (pp = curp->p_pptr; pp != NULL; pp = pp->p_pptr)
335 if (pp == p) {
336 lwkt_reltoken(&p->p_token);
337 PRELE(p);
338 return (EINVAL);
339 }
340
341 /* not owned by you, has done setuid (unless you're root) */
342 if ((p->p_ucred->cr_ruid != curp->p_ucred->cr_ruid) ||
343 (p->p_flags & P_SUGID)) {
344 if ((error = priv_check_cred(curp->p_ucred, PRIV_ROOT, 0)) != 0) {
345 lwkt_reltoken(&p->p_token);
346 PRELE(p);
347 return error;
348 }
349 }
350
351 /* can't trace init when securelevel > 0 */
352 if (securelevel > 0 && p->p_pid == 1) {
353 lwkt_reltoken(&p->p_token);
354 PRELE(p);
355 return EPERM;
356 }
357
358 /* OK */
359 break;
360
361 case PT_READ_I:
362 case PT_READ_D:
363 case PT_WRITE_I:
364 case PT_WRITE_D:
365 case PT_IO:
366 case PT_CONTINUE:
367 case PT_KILL:
368 case PT_STEP:
369 case PT_DETACH:
370 #ifdef PT_GETREGS
371 case PT_GETREGS:
372 #endif
373 #ifdef PT_SETREGS
374 case PT_SETREGS:
375 #endif
376 #ifdef PT_GETFPREGS
377 case PT_GETFPREGS:
378 #endif
379 #ifdef PT_SETFPREGS
380 case PT_SETFPREGS:
381 #endif
382 #ifdef PT_GETDBREGS
383 case PT_GETDBREGS:
384 #endif
385 #ifdef PT_SETDBREGS
386 case PT_SETDBREGS:
387 #endif
388 /* not being traced... */
389 if ((p->p_flags & P_TRACED) == 0) {
390 lwkt_reltoken(&p->p_token);
391 PRELE(p);
392 return EPERM;
393 }
394
395 /* not being traced by YOU */
396 if (p->p_pptr != curp) {
397 lwkt_reltoken(&p->p_token);
398 PRELE(p);
399 return EBUSY;
400 }
401
402 /* not currently stopped */
403 if (p->p_stat != SSTOP ||
404 (p->p_flags & P_WAITED) == 0) {
405 lwkt_reltoken(&p->p_token);
406 PRELE(p);
407 return EBUSY;
408 }
409
410 /* OK */
411 break;
412
413 default:
414 lwkt_reltoken(&p->p_token);
415 PRELE(p);
416 return EINVAL;
417 }
418
419 /* XXX lwp */
420 lp = FIRST_LWP_IN_PROC(p);
421 #ifdef FIX_SSTEP
422 /*
423 * Single step fixup ala procfs
424 */
425 FIX_SSTEP(lp);
426 #endif
427
428 /*
429 * Actually do the requests
430 */
431
432 *res = 0;
433
434 switch (req) {
435 case PT_TRACE_ME:
436 /* set my trace flag and "owner" so it can read/write me */
437 p->p_flags |= P_TRACED;
438 p->p_oppid = p->p_pptr->p_pid;
439 lwkt_reltoken(&p->p_token);
440 PRELE(p);
441 return 0;
442
443 case PT_ATTACH:
444 /* security check done above */
445 p->p_flags |= P_TRACED;
446 p->p_oppid = p->p_pptr->p_pid;
447 proc_reparent(p, curp);
448 data = SIGSTOP;
449 goto sendsig; /* in PT_CONTINUE below */
450
451 case PT_STEP:
452 case PT_CONTINUE:
453 case PT_DETACH:
454 /* Zero means do not send any signal */
455 if (data < 0 || data > _SIG_MAXSIG) {
456 lwkt_reltoken(&p->p_token);
457 PRELE(p);
458 return EINVAL;
459 }
460
461 LWPHOLD(lp);
462
463 if (req == PT_STEP) {
464 if ((error = ptrace_single_step (lp))) {
465 LWPRELE(lp);
466 lwkt_reltoken(&p->p_token);
467 PRELE(p);
468 return error;
469 }
470 }
471
472 if (addr != (void *)1) {
473 if ((error = ptrace_set_pc (lp,
474 (u_long)(uintfptr_t)addr))) {
475 LWPRELE(lp);
476 lwkt_reltoken(&p->p_token);
477 PRELE(p);
478 return error;
479 }
480 }
481 LWPRELE(lp);
482
483 if (req == PT_DETACH) {
484 /* reset process parent */
485 if (p->p_oppid != p->p_pptr->p_pid) {
486 struct proc *pp;
487
488 pp = pfind(p->p_oppid);
489 if (pp) {
490 proc_reparent(p, pp);
491 PRELE(pp);
492 }
493 }
494
495 p->p_flags &= ~(P_TRACED | P_WAITED);
496 p->p_oppid = 0;
497
498 /* should we send SIGCHLD? */
499 }
500
501 sendsig:
502 /*
503 * Deliver or queue signal. If the process is stopped
504 * force it to be SACTIVE again.
505 */
506 crit_enter();
507 if (p->p_stat == SSTOP) {
508 p->p_xstat = data;
509 proc_unstop(p, SSTOP);
510 } else if (data) {
511 ksignal(p, data);
512 }
513 crit_exit();
514 lwkt_reltoken(&p->p_token);
515 PRELE(p);
516 return 0;
517
518 case PT_WRITE_I:
519 case PT_WRITE_D:
520 write = 1;
521 /* fallthrough */
522 case PT_READ_I:
523 case PT_READ_D:
524 /*
525 * NOTE! uio_offset represents the offset in the target
526 * process. The iov is in the current process (the guy
527 * making the ptrace call) so uio_td must be the current
528 * process (though for a SYSSPACE transfer it doesn't
529 * really matter).
530 */
531 tmp = 0;
532 /* write = 0 set above */
533 iov.iov_base = write ? (caddr_t)&data : (caddr_t)&tmp;
534 iov.iov_len = sizeof(int);
535 uio.uio_iov = &iov;
536 uio.uio_iovcnt = 1;
537 uio.uio_offset = (off_t)(uintptr_t)addr;
538 uio.uio_resid = sizeof(int);
539 uio.uio_segflg = UIO_SYSSPACE;
540 uio.uio_rw = write ? UIO_WRITE : UIO_READ;
541 uio.uio_td = curthread;
542 error = procfs_domem(curp, lp, NULL, &uio);
543 if (uio.uio_resid != 0) {
544 /*
545 * XXX procfs_domem() doesn't currently return ENOSPC,
546 * so I think write() can bogusly return 0.
547 * XXX what happens for short writes? We don't want
548 * to write partial data.
549 * XXX procfs_domem() returns EPERM for other invalid
550 * addresses. Convert this to EINVAL. Does this
551 * clobber returns of EPERM for other reasons?
552 */
553 if (error == 0 || error == ENOSPC || error == EPERM)
554 error = EINVAL; /* EOF */
555 }
556 if (!write)
557 *res = tmp;
558 lwkt_reltoken(&p->p_token);
559 PRELE(p);
560 return (error);
561
562 case PT_IO:
563 /*
564 * NOTE! uio_offset represents the offset in the target
565 * process. The iov is in the current process (the guy
566 * making the ptrace call) so uio_td must be the current
567 * process.
568 */
569 piod = addr;
570 iov.iov_base = piod->piod_addr;
571 iov.iov_len = piod->piod_len;
572 uio.uio_iov = &iov;
573 uio.uio_iovcnt = 1;
574 uio.uio_offset = (off_t)(uintptr_t)piod->piod_offs;
575 uio.uio_resid = piod->piod_len;
576 uio.uio_segflg = UIO_USERSPACE;
577 uio.uio_td = curthread;
578 switch (piod->piod_op) {
579 case PIOD_READ_D:
580 case PIOD_READ_I:
581 uio.uio_rw = UIO_READ;
582 break;
583 case PIOD_WRITE_D:
584 case PIOD_WRITE_I:
585 uio.uio_rw = UIO_WRITE;
586 break;
587 default:
588 lwkt_reltoken(&p->p_token);
589 PRELE(p);
590 return (EINVAL);
591 }
592 error = procfs_domem(curp, lp, NULL, &uio);
593 piod->piod_len -= uio.uio_resid;
594 lwkt_reltoken(&p->p_token);
595 PRELE(p);
596 return (error);
597
598 case PT_KILL:
599 data = SIGKILL;
600 goto sendsig; /* in PT_CONTINUE above */
601
602 #ifdef PT_SETREGS
603 case PT_SETREGS:
604 write = 1;
605 /* fallthrough */
606 #endif /* PT_SETREGS */
607 #ifdef PT_GETREGS
608 case PT_GETREGS:
609 /* write = 0 above */
610 #endif /* PT_SETREGS */
611 #if defined(PT_SETREGS) || defined(PT_GETREGS)
612 if (!procfs_validregs(lp)) {
613 lwkt_reltoken(&p->p_token);
614 PRELE(p);
615 return EINVAL;
616 } else {
617 iov.iov_base = addr;
618 iov.iov_len = sizeof(struct reg);
619 uio.uio_iov = &iov;
620 uio.uio_iovcnt = 1;
621 uio.uio_offset = 0;
622 uio.uio_resid = sizeof(struct reg);
623 uio.uio_segflg = UIO_SYSSPACE;
624 uio.uio_rw = write ? UIO_WRITE : UIO_READ;
625 uio.uio_td = curthread;
626 t = procfs_doregs(curp, lp, NULL, &uio);
627 lwkt_reltoken(&p->p_token);
628 PRELE(p);
629 return t;
630 }
631 #endif /* defined(PT_SETREGS) || defined(PT_GETREGS) */
632
633 #ifdef PT_SETFPREGS
634 case PT_SETFPREGS:
635 write = 1;
636 /* fallthrough */
637 #endif /* PT_SETFPREGS */
638 #ifdef PT_GETFPREGS
639 case PT_GETFPREGS:
640 /* write = 0 above */
641 #endif /* PT_SETFPREGS */
642 #if defined(PT_SETFPREGS) || defined(PT_GETFPREGS)
643 if (!procfs_validfpregs(lp)) {
644 lwkt_reltoken(&p->p_token);
645 PRELE(p);
646 return EINVAL;
647 } else {
648 iov.iov_base = addr;
649 iov.iov_len = sizeof(struct fpreg);
650 uio.uio_iov = &iov;
651 uio.uio_iovcnt = 1;
652 uio.uio_offset = 0;
653 uio.uio_resid = sizeof(struct fpreg);
654 uio.uio_segflg = UIO_SYSSPACE;
655 uio.uio_rw = write ? UIO_WRITE : UIO_READ;
656 uio.uio_td = curthread;
657 t = procfs_dofpregs(curp, lp, NULL, &uio);
658 lwkt_reltoken(&p->p_token);
659 PRELE(p);
660 return t;
661 }
662 #endif /* defined(PT_SETFPREGS) || defined(PT_GETFPREGS) */
663
664 #ifdef PT_SETDBREGS
665 case PT_SETDBREGS:
666 write = 1;
667 /* fallthrough */
668 #endif /* PT_SETDBREGS */
669 #ifdef PT_GETDBREGS
670 case PT_GETDBREGS:
671 /* write = 0 above */
672 #endif /* PT_SETDBREGS */
673 #if defined(PT_SETDBREGS) || defined(PT_GETDBREGS)
674 if (!procfs_validdbregs(lp)) {
675 lwkt_reltoken(&p->p_token);
676 PRELE(p);
677 return EINVAL;
678 } else {
679 iov.iov_base = addr;
680 iov.iov_len = sizeof(struct dbreg);
681 uio.uio_iov = &iov;
682 uio.uio_iovcnt = 1;
683 uio.uio_offset = 0;
684 uio.uio_resid = sizeof(struct dbreg);
685 uio.uio_segflg = UIO_SYSSPACE;
686 uio.uio_rw = write ? UIO_WRITE : UIO_READ;
687 uio.uio_td = curthread;
688 t = procfs_dodbregs(curp, lp, NULL, &uio);
689 lwkt_reltoken(&p->p_token);
690 PRELE(p);
691 return t;
692 }
693 #endif /* defined(PT_SETDBREGS) || defined(PT_GETDBREGS) */
694
695 default:
696 break;
697 }
698
699 lwkt_reltoken(&p->p_token);
700 PRELE(p);
701
702 return 0;
703 }
704
705 int
706 trace_req(struct proc *p)
707 {
708 return 1;
709 }
710
711 /*
712 * stopevent()
713 *
714 * Stop a process because of a procfs event. Stay stopped until p->p_step
715 * is cleared (cleared by PIOCCONT in procfs).
716 *
717 * MPSAFE
718 */
719 void
720 stopevent(struct proc *p, unsigned int event, unsigned int val)
721 {
722 /*
723 * Set event info. Recheck p_stops in case we are
724 * racing a close() on procfs.
725 */
726 spin_lock(&p->p_spin);
727 if ((p->p_stops & event) == 0) {
728 spin_unlock(&p->p_spin);
729 return;
730 }
731 p->p_xstat = val;
732 p->p_stype = event;
733 p->p_step = 1;
734 tsleep_interlock(&p->p_step, 0);
735 spin_unlock(&p->p_spin);
736
737 /*
738 * Wakeup any PIOCWAITing procs and wait for p_step to
739 * be cleared.
740 */
741 for (;;) {
742 wakeup(&p->p_stype);
743 tsleep(&p->p_step, PINTERLOCKED, "stopevent", 0);
744 spin_lock(&p->p_spin);
745 if (p->p_step == 0) {
746 spin_unlock(&p->p_spin);
747 break;
748 }
749 tsleep_interlock(&p->p_step, 0);
750 spin_unlock(&p->p_spin);
751 }
752 }
753
DragonFly BSD