1 /* Multi-threaded debugging support for Linux (LWP layer).
2 Copyright 2000, 2001 Free Software Foundation, Inc.
4 This file is part of GDB.
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2 of the License, or
9 (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, write to the Free Software
18 Foundation, Inc., 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
23 #include "gdb_assert.h"
26 #include <sys/ptrace.h>
29 #include "gdbthread.h"
35 static int debug_lin_lwp
;
36 extern const char *strsignal (int sig
);
38 /* On Linux there are no real LWP's. The closest thing to LWP's are
39 processes sharing the same VM space. A multi-threaded process is
40 basically a group of such processes. However, such a grouping is
41 almost entirely a user-space issue; the kernel doesn't enforce such
42 a grouping at all (this might change in the future). In general,
43 we'll rely on the threads library (i.e. the LinuxThreads library)
44 to provide such a grouping.
46 It is perfectly well possible to write a multi-threaded application
47 without the assistance of a threads library, by using the clone
48 system call directly. This module should be able to give some
49 rudimentary support for debugging such applications if developers
50 specify the CLONE_PTRACE flag in the clone system call, and are
51 using Linux 2.4 or above.
53 Note that there are some peculiarities in Linux that affect this
56 - In general one should specify the __WCLONE flag to waitpid in
57 order to make it report events for any of the cloned processes
58 (and leave it out for the initial process). However, if a cloned
59 process has exited the exit status is only reported if the
60 __WCLONE flag is absent. Linux 2.4 has a __WALL flag, but we
61 cannot use it since GDB must work on older systems too.
63 - When a traced, cloned process exits and is waited for by the
64 debugger, the kernel reassigns it to the original parent and
65 keeps it around as a "zombie". Somehow, the LinuxThreads library
66 doesn't notice this, which leads to the "zombie problem": When
67 debugged a multi-threaded process that spawns a lot of threads
68 will run out of processes, even if the threads exit, because the
69 "zombies" stay around. */
71 /* Structure describing a LWP. */
74 /* The process id of the LWP. This is a combination of the LWP id
75 and overall process id. */
78 /* Non-zero if we sent this LWP a SIGSTOP (but the LWP didn't report
82 /* Non-zero if this LWP is stopped. */
85 /* Non-zero if this LWP will be/has been resumed. Note that an LWP
86 can be marked both as stopped and resumed at the same time. This
87 happens if we try to resume an LWP that has a wait status
88 pending. We shouldn't let the LWP run until that wait status has
89 been processed, but we should not report that wait status if GDB
90 didn't try to let the LWP run. */
93 /* If non-zero, a pending wait status. */
96 /* Non-zero if we were stepping this LWP. */
99 /* Next LWP in list. */
100 struct lwp_info
*next
;
103 /* List of known LWPs. */
104 static struct lwp_info
*lwp_list
;
106 /* Number of LWPs in the list. */
109 /* Non-zero if we're running in "threaded" mode. */
113 #define GET_LWP(ptid) ptid_get_lwp (ptid)
114 #define GET_PID(ptid) ptid_get_pid (ptid)
115 #define is_lwp(ptid) (GET_LWP (ptid) != 0)
116 #define BUILD_LWP(lwp, pid) ptid_build (pid, lwp, 0)
118 #define is_cloned(pid) (GET_LWP (pid) != GET_PID (pid))
120 /* If the last reported event was a SIGTRAP, this variable is set to
121 the process id of the LWP/thread that got it. */
125 /* This module's target-specific operations. */
126 static struct target_ops lin_lwp_ops
;
128 /* The standard child operations. */
129 extern struct target_ops child_ops
;
131 /* Since we cannot wait (in lin_lwp_wait) for the initial process and
132 any cloned processes with a single call to waitpid, we have to use
133 the WNOHANG flag and call waitpid in a loop. To optimize
134 things a bit we use `sigsuspend' to wake us up when a process has
135 something to report (it will send us a SIGCHLD if it has). To make
136 this work we have to juggle with the signal mask. We save the
137 original signal mask such that we can restore it before creating a
138 new process in order to avoid blocking certain signals in the
139 inferior. We then block SIGCHLD during the waitpid/sigsuspend
142 /* Original signal mask. */
143 static sigset_t normal_mask
;
145 /* Signal mask for use with sigsuspend in lin_lwp_wait, initialized in
146 _initialize_lin_lwp. */
147 static sigset_t suspend_mask
;
149 /* Signals to block to make that sigsuspend work. */
150 static sigset_t blocked_mask
;
153 /* Prototypes for local functions. */
154 static int stop_wait_callback (struct lwp_info
*lp
, void *data
);
157 /* Initialize the list of LWPs. Note that this module, contrary to
158 what GDB's generic threads layer does for its thread list,
159 re-initializes the LWP lists whenever we mourn or detach (which
160 doesn't involve mourning) the inferior. */
165 struct lwp_info
*lp
, *lpnext
;
167 for (lp
= lwp_list
; lp
; lp
= lpnext
)
178 /* Add the LWP specified by PID to the list. If this causes the
179 number of LWPs to become larger than one, go into "threaded" mode.
180 Return a pointer to the structure describing the new LWP. */
182 static struct lwp_info
*
183 add_lwp (ptid_t ptid
)
187 gdb_assert (is_lwp (ptid
));
189 lp
= (struct lwp_info
*) xmalloc (sizeof (struct lwp_info
));
191 memset (lp
, 0, sizeof (struct lwp_info
));
203 /* Remove the LWP specified by PID from the list. */
206 delete_lwp (ptid_t ptid
)
208 struct lwp_info
*lp
, *lpprev
;
212 for (lp
= lwp_list
; lp
; lpprev
= lp
, lp
= lp
->next
)
213 if (ptid_equal (lp
->ptid
, ptid
))
219 /* We don't go back to "non-threaded" mode if the number of threads
220 becomes less than two. */
224 lpprev
->next
= lp
->next
;
231 /* Return a pointer to the structure describing the LWP corresponding
232 to PID. If no corresponding LWP could be found, return NULL. */
234 static struct lwp_info
*
235 find_lwp_pid (ptid_t ptid
)
241 lwp
= GET_LWP (ptid
);
243 lwp
= GET_PID (ptid
);
245 for (lp
= lwp_list
; lp
; lp
= lp
->next
)
246 if (lwp
== GET_LWP (lp
->ptid
))
252 /* Call CALLBACK with its second argument set to DATA for every LWP in
253 the list. If CALLBACK returns 1 for a particular LWP, return a
254 pointer to the structure describing that LWP immediately.
255 Otherwise return NULL. */
258 iterate_over_lwps (int (*callback
) (struct lwp_info
*, void *), void *data
)
260 struct lwp_info
*lp
, *lpnext
;
262 for (lp
= lwp_list
; lp
; lp
= lpnext
)
265 if ((*callback
) (lp
, data
))
273 /* Implementation of the PREPARE_TO_PROCEED hook for the Linux LWP
276 Note that this implementation is potentially redundant now that
277 default_prepare_to_proceed() has been added.
279 FIXME This may not support switching threads after Ctrl-C
280 correctly. The default implementation does support this. */
283 lin_lwp_prepare_to_proceed (void)
285 if (! ptid_equal (trap_ptid
, null_ptid
)
286 && ! ptid_equal (inferior_ptid
, trap_ptid
))
288 /* Switched over from TRAP_PID. */
289 CORE_ADDR stop_pc
= read_pc ();
292 /* Avoid switching where it wouldn't do any good, i.e. if both
293 threads are at the same breakpoint. */
294 trap_pc
= read_pc_pid (trap_ptid
);
295 if (trap_pc
!= stop_pc
&& breakpoint_here_p (trap_pc
))
297 /* User hasn't deleted the breakpoint. Return non-zero, and
298 switch back to TRAP_PID. */
299 inferior_ptid
= trap_ptid
;
301 /* FIXME: Is this stuff really necessary? */
302 flush_cached_frames ();
303 registers_changed ();
315 lin_lwp_open (char *args
, int from_tty
)
317 push_target (&lin_lwp_ops
);
321 /* Attach to the LWP specified by PID. If VERBOSE is non-zero, print
322 a message telling the user that a new LWP has been added to the
326 lin_lwp_attach_lwp (ptid_t ptid
, int verbose
)
330 gdb_assert (is_lwp (ptid
));
333 printf_filtered ("[New %s]\n", target_pid_to_str (ptid
));
335 /* We assume that we're already tracing the initial process. */
336 if (is_cloned (ptid
) && ptrace (PTRACE_ATTACH
, GET_LWP (ptid
), 0, 0) < 0)
337 error ("Can't attach %s: %s", target_pid_to_str (ptid
), strerror (errno
));
339 lp
= find_lwp_pid (ptid
);
343 if (is_cloned (ptid
))
346 stop_wait_callback (lp
, NULL
);
351 lin_lwp_attach (char *args
, int from_tty
)
355 /* FIXME: We should probably accept a list of process id's, and
356 attach all of them. */
357 child_ops
.to_attach (args
, from_tty
);
359 /* Add the initial process as the first LWP to the list. */
360 lp
= add_lwp (BUILD_LWP (PIDGET (inferior_ptid
), PIDGET (inferior_ptid
)));
362 /* Make sure the initial process is stopped. The user-level threads
363 layer might want to poke around in the inferior, and that won't
364 work if things haven't stabilized yet. */
366 stop_wait_callback (lp
, NULL
);
367 gdb_assert (lp
->status
== 0);
369 /* Fake the SIGSTOP that core GDB expects. */
370 lp
->status
= W_STOPCODE (SIGSTOP
);
375 detach_callback (struct lwp_info
*lp
, void *data
)
377 gdb_assert (lp
->status
== 0 || WIFSTOPPED (lp
->status
));
379 if (debug_lin_lwp
&& lp
->status
)
380 fprintf_unfiltered (gdb_stdlog
, "Pending %s for LWP %ld on detach.\n",
381 strsignal (WSTOPSIG (lp
->status
)), GET_LWP (lp
->ptid
));
383 while (lp
->signalled
&& lp
->stopped
)
385 if (ptrace (PTRACE_CONT
, GET_LWP (lp
->ptid
), 0,
386 WSTOPSIG (lp
->status
)) < 0)
387 error ("Can't continue %s: %s", target_pid_to_str (lp
->ptid
),
393 stop_wait_callback (lp
, NULL
);
395 gdb_assert (lp
->status
== 0 || WIFSTOPPED (lp
->status
));
398 if (is_cloned (lp
->ptid
))
400 if (ptrace (PTRACE_DETACH
, GET_LWP (lp
->ptid
), 0,
401 WSTOPSIG (lp
->status
)) < 0)
402 error ("Can't detach %s: %s", target_pid_to_str (lp
->ptid
),
405 delete_lwp (lp
->ptid
);
412 lin_lwp_detach (char *args
, int from_tty
)
414 iterate_over_lwps (detach_callback
, NULL
);
416 /* Only the initial (uncloned) process should be left right now. */
417 gdb_assert (num_lwps
== 1);
419 trap_ptid
= null_ptid
;
421 /* Destroy LWP info; it's no longer valid. */
424 /* Restore the original signal mask. */
425 sigprocmask (SIG_SETMASK
, &normal_mask
, NULL
);
426 sigemptyset (&blocked_mask
);
428 inferior_ptid
= pid_to_ptid (GET_PID (inferior_ptid
));
429 child_ops
.to_detach (args
, from_tty
);
433 struct private_thread_info
438 /* Return non-zero if TP corresponds to the LWP specified by DATA
439 (which is assumed to be a pointer to a `struct lwp_info'. */
442 find_lwp_callback (struct thread_info
*tp
, void *data
)
444 struct lwp_info
*lp
= data
;
446 if (tp
->private->lwpid
== GET_LWP (lp
->ptid
))
455 resume_callback (struct lwp_info
*lp
, void *data
)
457 if (lp
->stopped
&& lp
->status
== 0)
459 struct thread_info
*tp
;
462 /* FIXME: kettenis/2000-08-26: This should really be handled
463 properly by core GDB. */
465 tp
= find_thread_pid (lp
->ptid
);
467 tp
= iterate_over_threads (find_lwp_callback
, lp
);
470 /* If we were previously stepping the thread, and now continue
471 the thread we must invalidate the stepping range. However,
472 if there is a step_resume breakpoint for this thread, we must
473 preserve the stepping range to make it possible to continue
474 stepping once we hit it. */
475 if (tp
->step_range_end
&& tp
->step_resume_breakpoint
== NULL
)
477 gdb_assert (lp
->step
);
478 tp
->step_range_start
= tp
->step_range_end
= 0;
482 child_resume (pid_to_ptid (GET_LWP (lp
->ptid
)), 0, TARGET_SIGNAL_0
);
491 resume_clear_callback (struct lwp_info
*lp
, void *data
)
498 resume_set_callback (struct lwp_info
*lp
, void *data
)
505 lin_lwp_resume (ptid_t ptid
, int step
, enum target_signal signo
)
510 /* Apparently the interpretation of PID is dependent on STEP: If
511 STEP is non-zero, a specific PID means `step only this process
512 id'. But if STEP is zero, then PID means `continue *all*
513 processes, but give the signal only to this one'. */
514 resume_all
= (PIDGET (ptid
) == -1) || !step
;
517 iterate_over_lwps (resume_set_callback
, NULL
);
519 iterate_over_lwps (resume_clear_callback
, NULL
);
521 /* If PID is -1, it's the current inferior that should be
522 handled specially. */
523 if (PIDGET (ptid
) == -1)
524 ptid
= inferior_ptid
;
526 lp
= find_lwp_pid (ptid
);
529 ptid
= pid_to_ptid (GET_LWP (lp
->ptid
));
531 /* Remember if we're stepping. */
534 /* Mark this LWP as resumed. */
537 /* If we have a pending wait status for this thread, there is no
538 point in resuming the process. */
541 /* FIXME: What should we do if we are supposed to continue
542 this thread with a signal? */
543 gdb_assert (signo
== TARGET_SIGNAL_0
);
547 /* Mark LWP as not stopped to prevent it from being continued by
553 iterate_over_lwps (resume_callback
, NULL
);
555 child_resume (ptid
, step
, signo
);
559 /* Send a SIGSTOP to LP. */
562 stop_callback (struct lwp_info
*lp
, void *data
)
564 if (! lp
->stopped
&& ! lp
->signalled
)
568 ret
= kill (GET_LWP (lp
->ptid
), SIGSTOP
);
569 gdb_assert (ret
== 0);
572 gdb_assert (lp
->status
== 0);
578 /* Wait until LP is stopped. */
581 stop_wait_callback (struct lwp_info
*lp
, void *data
)
583 if (! lp
->stopped
&& lp
->signalled
)
588 gdb_assert (lp
->status
== 0);
590 pid
= waitpid (GET_LWP (lp
->ptid
), &status
,
591 is_cloned (lp
->ptid
) ? __WCLONE
: 0);
592 if (pid
== -1 && errno
== ECHILD
)
593 /* OK, the proccess has disappeared. We'll catch the actual
594 exit event in lin_lwp_wait. */
597 gdb_assert (pid
== GET_LWP (lp
->ptid
));
599 if (WIFEXITED (status
) || WIFSIGNALED (status
))
601 gdb_assert (num_lwps
> 1);
603 if (in_thread_list (lp
->ptid
))
605 /* Core GDB cannot deal with us deleting the current
607 if (!ptid_equal (lp
->ptid
, inferior_ptid
))
608 delete_thread (lp
->ptid
);
609 printf_unfiltered ("[%s exited]\n",
610 target_pid_to_str (lp
->ptid
));
613 fprintf_unfiltered (gdb_stdlog
,
614 "%s exited.\n", target_pid_to_str (lp
->ptid
));
616 delete_lwp (lp
->ptid
);
620 gdb_assert (WIFSTOPPED (status
));
622 if (WSTOPSIG (status
) != SIGSTOP
)
624 if (WSTOPSIG (status
) == SIGTRAP
)
626 /* If a LWP other than the LWP that we're reporting an
627 event for has hit a GDB breakpoint (as opposed to
628 some random trap signal), then just arrange for it to
629 hit it again later. We don't keep the SIGTRAP status
630 and don't forward the SIGTRAP signal to the LWP. We
631 will handle the current event, eventually we will
632 resume all LWPs, and this one will get its breakpoint
635 If we do not do this, then we run the risk that the
636 user will delete or disable the breakpoint, but the
637 thread will have already tripped on it. */
639 /* Now resume this LWP and get the SIGSTOP event. */
640 ptrace (PTRACE_CONT
, GET_LWP (lp
->ptid
), 0, 0);
643 fprintf_unfiltered (gdb_stderr
,
644 "SWC: Candidate SIGTRAP event in %ld\n",
647 /* Hold the SIGTRAP for handling by lin_lwp_wait. */
648 stop_wait_callback (lp
, data
);
649 /* If there's another event, throw it back into the queue. */
651 kill (GET_LWP (lp
->ptid
), WSTOPSIG (lp
->status
));
652 /* Save the sigtrap event. */
656 else if (WSTOPSIG (status
) == SIGINT
&&
657 signal_pass_state (SIGINT
) == 0)
659 /* Since SIGINT gets forwarded to the entire process group
660 (in the case where ^C/BREAK is typed at the tty/console),
661 just ignore all SIGINT events from all lwp's except for
662 the one that was caught by lin_lwp_wait. */
664 /* Now resume this LWP and get the SIGSTOP event. */
665 ptrace (PTRACE_CONT
, GET_LWP (lp
->ptid
), 0, 0);
666 return stop_wait_callback (lp
, data
);
670 /* The thread was stopped with a signal other than
671 SIGSTOP, and didn't accidentally trip a breakpoint. */
675 fprintf_unfiltered (gdb_stderr
,
676 "SWC: Pending event %d in %ld\n",
677 WSTOPSIG (status
), GET_LWP (lp
->ptid
));
679 /* Now resume this LWP and get the SIGSTOP event. */
680 ptrace (PTRACE_CONT
, GET_LWP (lp
->ptid
), 0, 0);
682 /* Hold this event/waitstatus while we check to see if
683 there are any more (we still want to get that SIGSTOP). */
684 stop_wait_callback (lp
, data
);
685 /* If the lp->status field is still empty, use it to hold
686 this event. If not, then this event must be returned
687 to the event queue of the LWP. */
691 kill (GET_LWP (lp
->ptid
), WSTOPSIG (status
));
697 /* We caught the SIGSTOP that we intended to catch, so
698 there's no SIGSTOP pending. */
707 /* Return non-zero if LP has a wait status pending. */
710 status_callback (struct lwp_info
*lp
, void *data
)
712 /* Only report a pending wait status if we pretend that this has
713 indeed been resumed. */
714 return (lp
->status
!= 0 && lp
->resumed
);
717 /* Return non-zero if LP isn't stopped. */
720 running_callback (struct lwp_info
*lp
, void *data
)
722 return (lp
->stopped
== 0);
725 /* Count the LWP's that have had events. */
728 count_events_callback (struct lwp_info
*lp
, void *data
)
732 /* Count only threads that have a SIGTRAP pending. */
733 if (lp
->status
!= 0 &&
734 WIFSTOPPED (lp
->status
) &&
735 WSTOPSIG (lp
->status
) == SIGTRAP
&&
736 count
!= NULL
) /* paranoia */
742 /* Select the LWP (if any) that is currently being single-stepped. */
745 select_singlestep_lwp_callback (struct lwp_info
*lp
, void *data
)
747 if (lp
->step
&& lp
->status
!= 0)
753 /* Select the Nth LWP that has had a SIGTRAP event. */
756 select_event_lwp_callback (struct lwp_info
*lp
, void *data
)
758 int *selector
= data
;
760 /* Select only threads that have a SIGTRAP event pending. */
761 if (lp
->status
!= 0 &&
762 WIFSTOPPED (lp
->status
) &&
763 WSTOPSIG (lp
->status
) == SIGTRAP
&&
764 selector
!= NULL
) /* paranoia */
765 if ((*selector
)-- == 0)
772 cancel_breakpoints_callback (struct lwp_info
*lp
, void *data
)
774 struct lwp_info
*event_lp
= data
;
776 if (lp
!= event_lp
&&
778 WIFSTOPPED (lp
->status
) &&
779 WSTOPSIG (lp
->status
) == SIGTRAP
&&
780 breakpoint_inserted_here_p (read_pc_pid (lp
->ptid
) -
781 DECR_PC_AFTER_BREAK
))
785 fprintf_unfiltered (gdb_stdlog
,
786 "Push back BP for %ld\n",
789 /* For each lp except the event lp, if there was a trap,
790 set the PC to before the trap. */
791 if (DECR_PC_AFTER_BREAK
)
793 write_pc_pid (read_pc_pid (lp
->ptid
) - DECR_PC_AFTER_BREAK
,
801 /* Select one LWP out of those that have events to be the event thread. */
804 select_event_lwp (struct lwp_info
**orig_lp
, int *status
)
808 struct lwp_info
*event_lp
;
810 /* Give preference to any LWP that is being single-stepped. */
811 event_lp
= iterate_over_lwps (select_singlestep_lwp_callback
, NULL
);
812 if (event_lp
!= NULL
)
815 fprintf_unfiltered (gdb_stdlog
,
816 "Select singlestep lwp %ld\n",
817 GET_LWP (event_lp
->ptid
));
821 /* No single-stepping LWP. Select one at random, out of those
822 which have had SIGTRAP events. */
824 /* First see how many SIGTRAP events we have. */
825 iterate_over_lwps (count_events_callback
, (void *) &num_events
);
827 /* OK, now randomly pick the Nth LWP of those that have had SIGTRAP. */
828 random_selector
= (int)
829 ((num_events
* (double) rand ()) / (RAND_MAX
+ 1.0));
834 fprintf_unfiltered (gdb_stdlog
,
835 "Found %d SIGTRAP events, selecting #%d\n",
836 num_events
, random_selector
);
837 else if (num_events
<= 0)
838 fprintf_unfiltered (gdb_stdlog
,
839 "ERROR select_event_lwp %d events!\n",
843 event_lp
= iterate_over_lwps (select_event_lwp_callback
,
844 (void *) &random_selector
);
847 if (event_lp
!= NULL
)
849 /* "event_lp" is now the selected event thread.
850 If any other threads have had SIGTRAP events, these events
851 must now be cancelled, so that the respective thread will
852 trip the breakpoint again once it is resumed. */
853 iterate_over_lwps (cancel_breakpoints_callback
, (void *) event_lp
);
855 *status
= event_lp
->status
;
856 event_lp
->status
= 0;
860 /* Return non-zero if LP has been resumed. */
863 resumed_callback (struct lwp_info
*lp
, void *data
)
869 lin_lwp_wait (ptid_t ptid
, struct target_waitstatus
*ourstatus
)
871 struct lwp_info
*lp
= NULL
;
874 pid_t pid
= PIDGET (ptid
);
876 /* Make sure SIGCHLD is blocked. */
877 if (! sigismember (&blocked_mask
, SIGCHLD
))
879 sigaddset (&blocked_mask
, SIGCHLD
);
880 sigprocmask (SIG_BLOCK
, &blocked_mask
, NULL
);
885 /* Make sure there is at least one thread that has been resumed. */
886 gdb_assert (iterate_over_lwps (resumed_callback
, NULL
));
888 /* First check if there is a LWP with a wait status pending. */
891 /* Any LWP that's been resumed will do. */
892 lp
= iterate_over_lwps (status_callback
, NULL
);
898 if (debug_lin_lwp
&& status
)
899 fprintf_unfiltered (gdb_stdlog
,
900 "Using pending wait status %d for LWP %ld.\n",
901 WIFSTOPPED (status
) ? WSTOPSIG (status
) :
902 WIFSIGNALED (status
) ? WTERMSIG (status
) :
903 WEXITSTATUS (status
), GET_LWP (lp
->ptid
));
906 /* But if we don't fine one, we'll have to wait, and check both
907 cloned and uncloned processes. We start with the cloned
909 options
= __WCLONE
| WNOHANG
;
911 else if (is_lwp (ptid
))
914 fprintf_unfiltered (gdb_stdlog
,
915 "Waiting for specific LWP %ld.\n",
918 /* We have a specific LWP to check. */
919 lp
= find_lwp_pid (ptid
);
924 if (debug_lin_lwp
&& status
)
925 fprintf_unfiltered (gdb_stdlog
,
926 "Using pending wait status %d for LWP %ld.\n",
927 WIFSTOPPED (status
) ? WSTOPSIG (status
) :
928 WIFSIGNALED (status
) ? WTERMSIG (status
) :
929 WEXITSTATUS (status
), GET_LWP (lp
->ptid
));
931 /* If we have to wait, take into account whether PID is a cloned
932 process or not. And we have to convert it to something that
933 the layer beneath us can understand. */
934 options
= is_cloned (lp
->ptid
) ? __WCLONE
: 0;
935 pid
= GET_LWP (ptid
);
938 if (status
&& lp
->signalled
)
940 /* A pending SIGSTOP may interfere with the normal stream of
941 events. In a typical case where interference is a problem,
942 we have a SIGSTOP signal pending for LWP A while
943 single-stepping it, encounter an event in LWP B, and take the
944 pending SIGSTOP while trying to stop LWP A. After processing
945 the event in LWP B, LWP A is continued, and we'll never see
946 the SIGTRAP associated with the last time we were
947 single-stepping LWP A. */
949 /* Resume the thread. It should halt immediately returning the
951 child_resume (pid_to_ptid (GET_LWP (lp
->ptid
)), lp
->step
,
954 gdb_assert (lp
->resumed
);
956 /* This should catch the pending SIGSTOP. */
957 stop_wait_callback (lp
, NULL
);
960 set_sigint_trap (); /* Causes SIGINT to be passed on to the
968 lwpid
= waitpid (pid
, &status
, options
);
971 gdb_assert (pid
== -1 || lwpid
== pid
);
973 lp
= find_lwp_pid (pid_to_ptid (lwpid
));
976 lp
= add_lwp (BUILD_LWP (lwpid
, GET_PID (inferior_ptid
)));
979 gdb_assert (WIFSTOPPED (status
)
980 && WSTOPSIG (status
) == SIGSTOP
);
983 if (! in_thread_list (inferior_ptid
))
985 inferior_ptid
= BUILD_LWP (GET_PID (inferior_ptid
),
986 GET_PID (inferior_ptid
));
987 add_thread (inferior_ptid
);
990 add_thread (lp
->ptid
);
991 printf_unfiltered ("[New %s]\n",
992 target_pid_to_str (lp
->ptid
));
996 /* Make sure we don't report a TARGET_WAITKIND_EXITED or
997 TARGET_WAITKIND_SIGNALLED event if there are still LWP's
998 left in the process. */
999 if ((WIFEXITED (status
) || WIFSIGNALED (status
)) && num_lwps
> 1)
1001 if (in_thread_list (lp
->ptid
))
1003 /* Core GDB cannot deal with us deleting the current
1005 if (! ptid_equal (lp
->ptid
, inferior_ptid
))
1006 delete_thread (lp
->ptid
);
1007 printf_unfiltered ("[%s exited]\n",
1008 target_pid_to_str (lp
->ptid
));
1011 fprintf_unfiltered (gdb_stdlog
,
1013 target_pid_to_str (lp
->ptid
));
1015 delete_lwp (lp
->ptid
);
1017 /* Make sure there is at least one thread running. */
1018 gdb_assert (iterate_over_lwps (running_callback
, NULL
));
1020 /* Discard the event. */
1025 /* Make sure we don't report a SIGSTOP that we sent
1026 ourselves in an attempt to stop an LWP. */
1027 if (lp
->signalled
&& WIFSTOPPED (status
)
1028 && WSTOPSIG (status
) == SIGSTOP
)
1031 fprintf_unfiltered (gdb_stdlog
,
1032 "Delayed SIGSTOP caught for %s.\n",
1033 target_pid_to_str (lp
->ptid
));
1035 /* This is a delayed SIGSTOP. */
1038 child_resume (pid_to_ptid (GET_LWP (lp
->ptid
)), lp
->step
,
1041 gdb_assert (lp
->resumed
);
1043 /* Discard the event. */
1053 /* Alternate between checking cloned and uncloned processes. */
1054 options
^= __WCLONE
;
1056 /* And suspend every time we have checked both. */
1057 if (options
& __WCLONE
)
1058 sigsuspend (&suspend_mask
);
1061 /* We shouldn't end up here unless we want to try again. */
1062 gdb_assert (status
== 0);
1065 clear_sigio_trap ();
1066 clear_sigint_trap ();
1070 /* Don't report signals that GDB isn't interested in, such as
1071 signals that are neither printed nor stopped upon. Stopping all
1072 threads can be a bit time-consuming so if we want decent
1073 performance with heavily multi-threaded programs, especially when
1074 they're using a high frequency timer, we'd better avoid it if we
1077 if (WIFSTOPPED (status
))
1079 int signo
= target_signal_from_host (WSTOPSIG (status
));
1081 if (signal_stop_state (signo
) == 0
1082 && signal_print_state (signo
) == 0
1083 && signal_pass_state (signo
) == 1)
1085 /* FIMXE: kettenis/2001-06-06: Should we resume all threads
1086 here? It is not clear we should. GDB may not expect
1087 other threads to run. On the other hand, not resuming
1088 newly attached threads may cause an unwanted delay in
1089 getting them running. */
1090 child_resume (pid_to_ptid (GET_LWP (lp
->ptid
)), lp
->step
, signo
);
1097 /* This LWP is stopped now. */
1100 if (WIFSTOPPED (status
) && WSTOPSIG (status
) == SIGTRAP
)
1102 /* Save SIGTRAP event for select_event_lwp. */
1103 lp
->status
= status
;
1107 fprintf_unfiltered (gdb_stdlog
,
1108 "LLW: Candidate event %d in %ld\n",
1109 WSTOPSIG (status
), GET_LWP (lp
->ptid
));
1111 /* Now stop all other LWP's ... */
1112 iterate_over_lwps (stop_callback
, NULL
);
1114 /* ... and wait until all of them have reported back that they're no
1116 iterate_over_lwps (stop_wait_callback
, NULL
);
1118 /* MVS Now choose an event thread from among those that
1119 have had events. Giving equal priority to all threads
1120 that have had events helps prevent starvation. */
1122 select_event_lwp (&lp
, &status
);
1124 /* If we're not running in "threaded" mode, we'll report the bare
1127 if (WIFSTOPPED (status
) && WSTOPSIG (status
) == SIGTRAP
)
1129 trap_ptid
= (threaded
? lp
->ptid
: pid_to_ptid (GET_LWP (lp
->ptid
)));
1131 fprintf_unfiltered (gdb_stdlog
,
1132 "LLW: trap_ptid is %ld\n",
1133 GET_LWP (trap_ptid
));
1136 trap_ptid
= null_ptid
;
1138 store_waitstatus (ourstatus
, status
);
1139 return (threaded
? lp
->ptid
: pid_to_ptid (GET_LWP (lp
->ptid
)));
1143 kill_callback (struct lwp_info
*lp
, void *data
)
1145 ptrace (PTRACE_KILL
, GET_LWP (lp
->ptid
), 0, 0);
1150 kill_wait_callback (struct lwp_info
*lp
, void *data
)
1154 /* We must make sure that there are no pending events (delayed
1155 SIGSTOPs, pending SIGTRAPs, etc.) to make sure the current
1156 program doesn't interfere with any following debugging session. */
1158 /* For cloned processes we must check both with __WCLONE and
1159 without, since the exit status of a cloned process isn't reported
1161 if (is_cloned (lp
->ptid
))
1165 pid
= waitpid (GET_LWP (lp
->ptid
), NULL
, __WCLONE
);
1167 while (pid
== GET_LWP (lp
->ptid
));
1169 gdb_assert (pid
== -1 && errno
== ECHILD
);
1174 pid
= waitpid (GET_LWP (lp
->ptid
), NULL
, 0);
1176 while (pid
== GET_LWP (lp
->ptid
));
1178 gdb_assert (pid
== -1 && errno
== ECHILD
);
1185 /* Kill all LWP's ... */
1186 iterate_over_lwps (kill_callback
, NULL
);
1188 /* ... and wait until we've flushed all events. */
1189 iterate_over_lwps (kill_wait_callback
, NULL
);
1191 target_mourn_inferior ();
1195 lin_lwp_create_inferior (char *exec_file
, char *allargs
, char **env
)
1197 child_ops
.to_create_inferior (exec_file
, allargs
, env
);
1201 lin_lwp_mourn_inferior (void)
1203 trap_ptid
= null_ptid
;
1205 /* Destroy LWP info; it's no longer valid. */
1208 /* Restore the original signal mask. */
1209 sigprocmask (SIG_SETMASK
, &normal_mask
, NULL
);
1210 sigemptyset (&blocked_mask
);
1212 child_ops
.to_mourn_inferior ();
1216 lin_lwp_fetch_registers (int regno
)
1218 struct cleanup
*old_chain
= save_inferior_ptid ();
1220 if (is_lwp (inferior_ptid
))
1221 inferior_ptid
= pid_to_ptid (GET_LWP (inferior_ptid
));
1223 fetch_inferior_registers (regno
);
1225 do_cleanups (old_chain
);
1229 lin_lwp_store_registers (int regno
)
1231 struct cleanup
*old_chain
= save_inferior_ptid ();
1233 if (is_lwp (inferior_ptid
))
1234 inferior_ptid
= pid_to_ptid (GET_LWP (inferior_ptid
));
1236 store_inferior_registers (regno
);
1238 do_cleanups (old_chain
);
1242 lin_lwp_xfer_memory (CORE_ADDR memaddr
, char *myaddr
, int len
, int write
,
1243 struct mem_attrib
*attrib
,
1244 struct target_ops
*target
)
1246 struct cleanup
*old_chain
= save_inferior_ptid ();
1249 if (is_lwp (inferior_ptid
))
1250 inferior_ptid
= pid_to_ptid (GET_LWP (inferior_ptid
));
1252 xfer
= child_xfer_memory (memaddr
, myaddr
, len
, write
, attrib
, target
);
1254 do_cleanups (old_chain
);
1259 lin_lwp_thread_alive (ptid_t ptid
)
1261 gdb_assert (is_lwp (ptid
));
1264 ptrace (PTRACE_PEEKUSER
, GET_LWP (ptid
), 0, 0);
1272 lin_lwp_pid_to_str (ptid_t ptid
)
1274 static char buf
[64];
1278 snprintf (buf
, sizeof (buf
), "LWP %ld", GET_LWP (ptid
));
1282 return normal_pid_to_str (ptid
);
1286 init_lin_lwp_ops (void)
1289 lin_lwp_ops
.to_open
= lin_lwp_open
;
1291 lin_lwp_ops
.to_shortname
= "lwp-layer";
1292 lin_lwp_ops
.to_longname
= "lwp-layer";
1293 lin_lwp_ops
.to_doc
= "Low level threads support (LWP layer)";
1294 lin_lwp_ops
.to_attach
= lin_lwp_attach
;
1295 lin_lwp_ops
.to_detach
= lin_lwp_detach
;
1296 lin_lwp_ops
.to_resume
= lin_lwp_resume
;
1297 lin_lwp_ops
.to_wait
= lin_lwp_wait
;
1298 lin_lwp_ops
.to_fetch_registers
= lin_lwp_fetch_registers
;
1299 lin_lwp_ops
.to_store_registers
= lin_lwp_store_registers
;
1300 lin_lwp_ops
.to_xfer_memory
= lin_lwp_xfer_memory
;
1301 lin_lwp_ops
.to_kill
= lin_lwp_kill
;
1302 lin_lwp_ops
.to_create_inferior
= lin_lwp_create_inferior
;
1303 lin_lwp_ops
.to_mourn_inferior
= lin_lwp_mourn_inferior
;
1304 lin_lwp_ops
.to_thread_alive
= lin_lwp_thread_alive
;
1305 lin_lwp_ops
.to_pid_to_str
= lin_lwp_pid_to_str
;
1306 lin_lwp_ops
.to_stratum
= thread_stratum
;
1307 lin_lwp_ops
.to_has_thread_control
= tc_schedlock
;
1308 lin_lwp_ops
.to_magic
= OPS_MAGIC
;
1312 sigchld_handler (int signo
)
1314 /* Do nothing. The only reason for this handler is that it allows
1315 us to use sigsuspend in lin_lwp_wait above to wait for the
1316 arrival of a SIGCHLD. */
1320 _initialize_lin_lwp (void)
1322 struct sigaction action
;
1324 extern void thread_db_init (struct target_ops
*);
1326 init_lin_lwp_ops ();
1327 add_target (&lin_lwp_ops
);
1328 thread_db_init (&lin_lwp_ops
);
1330 /* Save the original signal mask. */
1331 sigprocmask (SIG_SETMASK
, NULL
, &normal_mask
);
1333 action
.sa_handler
= sigchld_handler
;
1334 sigemptyset (&action
.sa_mask
);
1335 action
.sa_flags
= 0;
1336 sigaction (SIGCHLD
, &action
, NULL
);
1338 /* Make sure we don't block SIGCHLD during a sigsuspend. */
1339 sigprocmask (SIG_SETMASK
, NULL
, &suspend_mask
);
1340 sigdelset (&suspend_mask
, SIGCHLD
);
1342 sigemptyset (&blocked_mask
);
1344 add_show_from_set (add_set_cmd ("lin-lwp", no_class
, var_zinteger
,
1345 (char *) &debug_lin_lwp
,
1346 "Set debugging of linux lwp module.\n\
1347 Enables printf debugging output.\n",
1353 /* FIXME: kettenis/2000-08-26: The stuff on this page is specific to
1354 the LinuxThreads library and therefore doesn't really belong here. */
1356 /* Read variable NAME in the target and return its value if found.
1357 Otherwise return zero. It is assumed that the type of the variable
1361 get_signo (const char *name
)
1363 struct minimal_symbol
*ms
;
1366 ms
= lookup_minimal_symbol (name
, NULL
, NULL
);
1370 if (target_read_memory (SYMBOL_VALUE_ADDRESS (ms
), (char *) &signo
,
1371 sizeof (signo
)) != 0)
1377 /* Return the set of signals used by the threads library in *SET. */
1380 lin_thread_get_thread_signals (sigset_t
*set
)
1382 struct sigaction action
;
1383 int restart
, cancel
;
1387 restart
= get_signo ("__pthread_sig_restart");
1391 cancel
= get_signo ("__pthread_sig_cancel");
1395 sigaddset (set
, restart
);
1396 sigaddset (set
, cancel
);
1398 /* The LinuxThreads library makes terminating threads send a special
1399 "cancel" signal instead of SIGCHLD. Make sure we catch those (to
1400 prevent them from terminating GDB itself, which is likely to be
1401 their default action) and treat them the same way as SIGCHLD. */
1403 action
.sa_handler
= sigchld_handler
;
1404 sigemptyset (&action
.sa_mask
);
1405 action
.sa_flags
= 0;
1406 sigaction (cancel
, &action
, NULL
);
1408 /* We block the "cancel" signal throughout this code ... */
1409 sigaddset (&blocked_mask
, cancel
);
1410 sigprocmask (SIG_BLOCK
, &blocked_mask
, NULL
);
1412 /* ... except during a sigsuspend. */
1413 sigdelset (&suspend_mask
, cancel
);