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Fix PR gdb/19676: Internal error in linux-thread.db.c if /proc not mounted

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If /proc is not mounted, GDB fails an assertion in find_new_threads_once:

 Continuing.
 .../src/gdb/linux-thread-db.c:1249: internal-error: find_new_threads_once: Assertion `!target_has_execution' failed.
 A problem internal to GDB has been detected,
 further debugging may prove unreliable.
 Quit this debugging session? (y or n)

That was supposed to catch misuses of td_ta_thr_iter, which is unsafe
for live debugging.  However, if /proc is not mounted, we still
fallback to using it.

I didn't bother with a warning, because GDB already prints several
others related to failing to open /proc files.

gdb/ChangeLog:
2016-03-15  Pedro Alves  <palves@redhat.com>

	PR gdb/19676
	* linux-thread-db.c (try_thread_db_load_1): Leave
	info->td_ta_thr_iter_p NULL iff debugging a live process and we
	have /proc access.
	(find_new_threads_once): Assert that we have a non-NULL
	info->td_ta_thr_iter_p instead of checking whether the target has
	execution.
This commit is contained in:
Pedro Alves 2016-03-15 16:33:04 +00:00
parent 16b4184277
commit 1eb2dbb8d7
2 changed files with 20 additions and 6 deletions
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10
gdb/ChangeLog
View file

@ -1,3 +1,13 @@
2016-03-15 Pedro Alves <palves@redhat.com>
PR gdb/19676
* linux-thread-db.c (try_thread_db_load_1): Leave
info->td_ta_thr_iter_p NULL iff debugging a live process and we
have /proc access.
(find_new_threads_once): Assert that we have a non-NULL
info->td_ta_thr_iter_p instead of checking whether the target has
execution.
2016-03-15 Pedro Alves <palves@redhat.com>
PR gdb/19676

16
gdb/linux-thread-db.c
View file

@ -564,7 +564,6 @@ try_thread_db_load_1 (struct thread_db_info *info)
/* These are essential. */
CHK (TDB_VERBOSE_DLSYM (info, td_ta_map_lwp2thr));
CHK (TDB_VERBOSE_DLSYM (info, td_ta_thr_iter));
CHK (TDB_VERBOSE_DLSYM (info, td_thr_validate));
CHK (TDB_VERBOSE_DLSYM (info, td_thr_get_info));
@ -572,10 +571,6 @@ try_thread_db_load_1 (struct thread_db_info *info)
TDB_DLSYM (info, td_thr_tls_get_addr);
TDB_DLSYM (info, td_thr_tlsbase);
#undef TDB_VERBOSE_DLSYM
#undef TDB_DLSYM
#undef CHK
/* It's best to avoid td_ta_thr_iter if possible. That walks data
structures in the inferior's address space that may be corrupted,
or, if the target is running, may change while we walk them. If
@ -587,6 +582,15 @@ try_thread_db_load_1 (struct thread_db_info *info)
currently on core targets, as it uses ptrace directly. */
if (target_has_execution
&& linux_proc_task_list_dir_exists (ptid_get_pid (inferior_ptid)))
info->td_ta_thr_iter_p = NULL;
else
CHK (TDB_VERBOSE_DLSYM (info, td_ta_thr_iter));
#undef TDB_VERBOSE_DLSYM
#undef TDB_DLSYM
#undef CHK
if (info->td_ta_thr_iter_p == NULL)
{
struct lwp_info *lp;
int pid = ptid_get_pid (inferior_ptid);
@ -1246,7 +1250,7 @@ find_new_threads_once (struct thread_db_info *info, int iteration,
data.new_threads = 0;
/* See comment in thread_db_update_thread_list. */
gdb_assert (!target_has_execution);
gdb_assert (info->td_ta_thr_iter_p != NULL);
TRY
{