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gcore, handle exited threads better

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An early (and since discarded) version of this series tried to make
exited threads have distinct PTID between each other, and that change
exposed a problem in linux-tdep.c...  This was exposed by the
gdb.threads/gcore-stale-thread.exp testcase, which is exactly about
calling gcore with an exited thread selected:

 (gdb) [Thread 0x7ffff7fb6740 (LWP 31523) exited]
 PASS: gdb.threads/gcore-stale-thread.exp: continue to breakpoint: break-here
 gcore /home/pedro/gdb/binutils-gdb/build/gdb/testsuite/outputs/gdb.threads/gcore-stale-thread/gcore-stale-thread.core
 /home/pedro/gdb/binutils-gdb/build/../src/gdb/inferior.c:66: internal-error: void set_current_inferior(inferior*): Assertion `inf != NULL' failed.
 A problem internal to GDB has been detected,

That was find_inferior_ptid being called on the "exited" ptid, which
on that previous (and discarded attempt) had pid==-1.  The problem is
that linux-tdep.c, where it looks for the signalled thread, isn't
considering exited threads.  Also, while at it, that code isn't
considering multi-target either, since it is using
iterate_over_threads which iterates over all threads of all targets.
Fixed by switching to range-for iteration instead.

gdb/ChangeLog:
2020-06-18  Pedro Alves  <palves@redhat.com>

	* linux-tdep.c (find_signalled_thread(thread_info *,void *)):
	Delete.
	(find_signalled_thread()): New, factored out from
	linux_make_corefile_notes and adjusted to handle exited threads.
	(linux_make_corefile_notes): Adjust to use the new
	find_signalled_thread.
This commit is contained in:
Pedro Alves 2020-06-18 21:28:18 +01:00
parent 41792d688a
commit 8df017996f
2 changed files with 42 additions and 27 deletions
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9
gdb/ChangeLog
View File

@ -1,3 +1,12 @@
2020-06-18 Pedro Alves <palves@redhat.com>
* linux-tdep.c (find_signalled_thread(thread_info *,void *)):
Delete.
(find_signalled_thread()): New, factored out from
linux_make_corefile_notes and adjusted to handle exited threads.
(linux_make_corefile_notes): Adjust to use the new
find_signalled_thread.
2020-06-18 Pedro Alves <palves@redhat.com>
* linux-tdep.c (btrace_fetch): Save/restore current thread instead

56
gdb/linux-tdep.c
View File

@ -1396,18 +1396,6 @@ linux_find_memory_regions (struct gdbarch *gdbarch,
&data);
}
/* Determine which signal stopped execution. */
static int
find_signalled_thread (struct thread_info *info, void *data)
{
if (info->suspend.stop_signal != GDB_SIGNAL_0
&& info->ptid.pid () == inferior_ptid.pid ())
return 1;
return 0;
}
/* This is used to pass information from
linux_make_mappings_corefile_notes through
linux_find_memory_regions_full. */
@ -1855,6 +1843,30 @@ linux_fill_prpsinfo (struct elf_internal_linux_prpsinfo *p)
return 1;
}
/* Find the signalled thread. In case there's more than one signalled
thread, prefer the current thread, if it is signalled. If no
thread was signalled, default to the current thread, unless it has
exited, in which case return NULL. */
static thread_info *
find_signalled_thread ()
{
thread_info *curr_thr = inferior_thread ();
if (curr_thr->state != THREAD_EXITED
&& curr_thr->suspend.stop_signal != GDB_SIGNAL_0)
return curr_thr;
for (thread_info *thr : current_inferior ()->non_exited_threads ())
if (thr->suspend.stop_signal != GDB_SIGNAL_0)
return thr;
/* Default to the current thread, unless it has exited. */
if (curr_thr->state != THREAD_EXITED)
return curr_thr;
return nullptr;
}
/* Build the note section for a corefile, and return it in a malloc
buffer. */
@ -1864,7 +1876,6 @@ linux_make_corefile_notes (struct gdbarch *gdbarch, bfd *obfd, int *note_size)
struct linux_corefile_thread_data thread_args;
struct elf_internal_linux_prpsinfo prpsinfo;
char *note_data = NULL;
struct thread_info *curr_thr, *signalled_thr;
if (! gdbarch_iterate_over_regset_sections_p (gdbarch))
return NULL;
@ -1892,25 +1903,20 @@ linux_make_corefile_notes (struct gdbarch *gdbarch, bfd *obfd, int *note_size)
}
/* Like the kernel, prefer dumping the signalled thread first.
"First thread" is what tools use to infer the signalled thread.
In case there's more than one signalled thread, prefer the
current thread, if it is signalled. */
curr_thr = inferior_thread ();
if (curr_thr->suspend.stop_signal != GDB_SIGNAL_0)
signalled_thr = curr_thr;
else
{
signalled_thr = iterate_over_threads (find_signalled_thread, NULL);
if (signalled_thr == NULL)
signalled_thr = curr_thr;
}
"First thread" is what tools use to infer the signalled
thread. */
thread_info *signalled_thr = find_signalled_thread ();
thread_args.gdbarch = gdbarch;
thread_args.obfd = obfd;
thread_args.note_data = note_data;
thread_args.note_size = note_size;
if (signalled_thr != nullptr)
thread_args.stop_signal = signalled_thr->suspend.stop_signal;
else
thread_args.stop_signal = GDB_SIGNAL_0;
if (signalled_thr != nullptr)
linux_corefile_thread (signalled_thr, &thread_args);
for (thread_info *thr : current_inferior ()->non_exited_threads ())
{