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Fix gdbserver regression exposed by gdb.threads/multi-create-ns-info-thr.exp

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Commit 8629910955 ("Add thread_db_notice_clone to gdbserver")
introduced calls into libthread_db without making sure that the
current thread is pointing to a know-stopped thread.  This resulted in
sometimes thread_db_notice_clone failing->find_one_thread failing like
this, as seen when running gdb.threads/multi-create-ns-info-thr.exp:

~~~
  Thread <6> executing
  Thread <7> executing
  gdbserver: PID mismatch!  Expected 27472, got 27471
  gdbserver: Cannot find thread after clone.

  Thread <1000> executing
  Thread <1001> executing
~~~

Things go south from here and sometimes that ends up resulting in
gdbserver crashing and the test failing.

gdb/gdbserver/ChangeLog:
2017-09-29  Pedro Alves  <palves@redhat.com>

	* linux-low.c (handle_extended_wait): Pass parent thread instead
	of process to thread_db_notice_clone.
	* linux-low.h (thread_db_notice_clone): Replace parent process
	parameter with parent thread parameter.
	* thread-db.c (find_one_thread): Add comment.
	(thread_db_notice_clone): Replace parent process parameter with
	parent thread parameter.  Temporarily switch to the parent thread.
This commit is contained in:
Pedro Alves 2017-09-29 13:06:34 +01:00
parent f6ac8c52c9
commit 94c207e097
4 changed files with 26 additions and 5 deletions
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10
gdb/gdbserver/ChangeLog
View File

@ -1,3 +1,13 @@
2017-09-29 Pedro Alves <palves@redhat.com>
* linux-low.c (handle_extended_wait): Pass parent thread instead
of process to thread_db_notice_clone.
* linux-low.h (thread_db_notice_clone): Replace parent process
parameter with parent thread parameter.
* thread-db.c (find_one_thread): Add comment.
(thread_db_notice_clone): Replace parent process parameter with
parent thread parameter. Temporarily switch to the parent thread.
2017-09-26 Sergio Durigan Junior <sergiodj@redhat.com>
* gdbthread.h: Include "common-gdbthread.h".

2
gdb/gdbserver/linux-low.c
View File

@ -656,7 +656,7 @@ handle_extended_wait (struct lwp_info **orig_event_lwp, int wstat)
new_lwp->status_pending = status;
}
thread_db_notice_clone (get_thread_process (event_thr), ptid);
thread_db_notice_clone (event_thr, ptid);
/* Don't report the event. */
return 1;

2
gdb/gdbserver/linux-low.h
View File

@ -417,7 +417,7 @@ int thread_db_look_up_one_symbol (const char *name, CORE_ADDR *addrp);
both the clone and the parent should be stopped. This function does
whatever is required have the clone under thread_db's control. */
void thread_db_notice_clone (struct process_info *proc, ptid_t lwp);
void thread_db_notice_clone (struct thread_info *parent_thr, ptid_t child_ptid);
bool thread_db_thread_handle (ptid_t ptid, gdb_byte **handle, int *handle_len);

17
gdb/gdbserver/thread-db.c
View File

@ -28,6 +28,7 @@ extern int debug_threads;
#include "nat/gdb_thread_db.h"
#include "gdb_vecs.h"
#include "nat/linux-procfs.h"
#include "common/scoped_restore.h"
#ifndef USE_LIBTHREAD_DB_DIRECTLY
#include <dlfcn.h>
@ -155,6 +156,9 @@ thread_db_state_str (td_thr_state_e state)
}
#endif
/* Get thread info about PTID, accessing memory via the current
thread. */
static int
find_one_thread (ptid_t ptid)
{
@ -887,15 +891,22 @@ thread_db_handle_monitor_command (char *mon)
/* See linux-low.h. */
void
thread_db_notice_clone (struct process_info *proc, ptid_t ptid)
thread_db_notice_clone (struct thread_info *parent_thr, ptid_t child_ptid)
{
struct thread_db *thread_db = proc->priv->thread_db;
process_info *parent_proc = get_thread_process (parent_thr);
struct thread_db *thread_db = parent_proc->priv->thread_db;
/* If the thread layer isn't initialized, return. It may just
be that the program uses clone, but does not use libthread_db. */
if (thread_db == NULL || !thread_db->all_symbols_looked_up)
return;
if (!find_one_thread (ptid))
/* find_one_thread calls into libthread_db which accesses memory via
the current thread. Temporarily switch to a thread we know is
stopped. */
scoped_restore restore_current_thread
= make_scoped_restore (&current_thread, parent_thr);
if (!find_one_thread (child_ptid))
warning ("Cannot find thread after clone.\n");
}