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Re: [patch] Fix for PR gdb/10838
On Saturday 14 November 2009 02:04:41, Paul Pluzhnikov wrote:
> Program terminated with signal 11, Segmentation fault.
>
> #0 0x0000000000408b75 in look_up_one_symbol (name=0x7f6dc44ee3a2
> "__nptl_threads_events", addrp=0x7fffcce720c8) at
> ../../../src/gdb/gdbserver/remote-utils.c:1374
> 1374 for (sym = proc->symbol_cache; sym; sym = sym->next)
>
> proc is NULL.
> Called from:
>
> #0 0x0000000000408b75 in look_up_one_symbol () at
> ../../../src/gdb/gdbserver/remote-utils.c:1374
> #1 0x000000000041ae0e in ps_pglobal_lookup () at
> ../../../src/gdb/gdbserver/proc-service.c:68
> #2 0x00007f6dc44ed60d in td_ta_clear_event () from /lib/libthread_db.so.1
> #3 0x000000000041ac8b in thread_db_free (proc=0x6311a0) at
> ../../../src/gdb/gdbserver/thread-db.c:773
> #4 0x0000000000411b44 in linux_remove_process (process=0x6311a0) at
> ../../../src/gdb/gdbserver/linux-low.c:267
Having look_up_one_symbol handle the null process case
tastes like papering over an earlier issue.
> Attached patch fixes that (tested with gdbserver on Linux/x86_64 this time).
Why are we calling td_ta_clear_event at all if the
process is gone? I think we should do that only if detaching,
like this (untested)? This is what GDB does too. The fact
that td_ta_clear_event wants to poke at a dead inferior is
a good indication of something not right. If the process is
gone (or we didn't actually manage to connect to
this thread_db), there's no event mask to clear.
Also, thread_db_free assumes its PROC argument is the
current inferior (due to the fact that proc-service.c
relies on current_inferior currently). This assumption
could/should be removed, but I'll leave that for
another day.
--
Pedro Alves
2009-11-16 Pedro Alves <pedro@codesourcery.com>
gdb/gdbserver/
* linux-low.c (linux_remove_process): Add `detaching' parameter.
Pass it to thread_db_free.
(linux_kill, linux_detach, linux_wait_1): Adjust to pass the
proper `detaching' argument to linux_remove_process.
* linux-low.h (thread_db_free): Add `detaching' parameter.
* thread-db.c (thread_db_init): Pass true as `detaching' argument
to thread_db_free.
(thread_db_free): Add `detaching' parameter. Only
call td_ta_clear_event if detaching from process.
---
gdb/gdbserver/linux-low.c | 10 +++++-----
gdb/gdbserver/linux-low.h | 2 +-
gdb/gdbserver/thread-db.c | 26 +++++++++++++-------------
3 files changed, 19 insertions(+), 19 deletions(-)
Index: src/gdb/gdbserver/linux-low.c
===================================================================
--- src.orig/gdb/gdbserver/linux-low.c 2009-11-16 02:07:20.000000000 +0000
+++ src/gdb/gdbserver/linux-low.c 2009-11-16 14:31:45.000000000 +0000
@@ -259,12 +259,12 @@ linux_add_process (int pid, int attached
also freeing all private data. */
static void
-linux_remove_process (struct process_info *process)
+linux_remove_process (struct process_info *process, int detaching)
{
struct process_info_private *priv = process->private;
#ifdef USE_THREAD_DB
- thread_db_free (process);
+ thread_db_free (process, detaching);
#endif
free (priv->arch_private);
@@ -663,7 +663,7 @@ linux_kill (int pid)
} while (lwpid > 0 && WIFSTOPPED (wstat));
delete_lwp (lwp);
- linux_remove_process (process);
+ linux_remove_process (process, 0);
return 0;
}
@@ -752,7 +752,7 @@ linux_detach (int pid)
delete_all_breakpoints ();
find_inferior (&all_threads, linux_detach_one_lwp, &pid);
- linux_remove_process (process);
+ linux_remove_process (process, 1);
return 0;
}
@@ -1378,7 +1378,7 @@ retry:
struct process_info *process = find_process_pid (pid);
delete_lwp (lwp);
- linux_remove_process (process);
+ linux_remove_process (process, 0);
current_inferior = NULL;
Index: src/gdb/gdbserver/linux-low.h
===================================================================
--- src.orig/gdb/gdbserver/linux-low.h 2009-11-16 02:07:20.000000000 +0000
+++ src/gdb/gdbserver/linux-low.h 2009-11-16 12:51:09.000000000 +0000
@@ -201,7 +201,7 @@ struct lwp_info *find_lwp_pid (ptid_t pt
/* From thread-db.c */
int thread_db_init (int use_events);
-void thread_db_free (struct process_info *);
+void thread_db_free (struct process_info *, int detaching);
int thread_db_handle_monitor_command (char *);
int thread_db_get_tls_address (struct thread_info *thread, CORE_ADDR offset,
CORE_ADDR load_module, CORE_ADDR *address);
Index: src/gdb/gdbserver/thread-db.c
===================================================================
--- src.orig/gdb/gdbserver/thread-db.c 2009-11-16 12:51:06.000000000 +0000
+++ src/gdb/gdbserver/thread-db.c 2009-11-16 13:51:22.000000000 +0000
@@ -737,7 +737,7 @@ thread_db_init (int use_events)
if (use_events && thread_db_enable_reporting () == 0)
{
/* Keep trying; maybe event reporting will work later. */
- thread_db_free (proc);
+ thread_db_free (proc, 0);
return 0;
}
thread_db_find_new_threads ();
@@ -752,38 +752,38 @@ thread_db_init (int use_events)
/* Disconnect from libthread_db and free resources. */
void
-thread_db_free (struct process_info *proc)
+thread_db_free (struct process_info *proc, int detaching)
{
struct thread_db *thread_db = proc->private->thread_db;
if (thread_db)
{
-#ifndef USE_LIBTHREAD_DB_DIRECTLY
td_err_e (*td_ta_delete_p) (td_thragent_t *);
td_err_e (*td_ta_clear_event_p) (const td_thragent_t *ta,
td_thr_events_t *event);
+#ifndef USE_LIBTHREAD_DB_DIRECTLY
td_ta_clear_event_p = dlsym (thread_db->handle, "td_ta_clear_event");
- if (td_ta_clear_event_p != NULL)
+ td_ta_delete_p = dlsym (thread_db->handle, "td_ta_delete");
+#else
+ td_ta_delete_p = &td_ta_delete;
+ td_ta_clear_event_p = &td_ta_clear_event;
+#endif
+
+ if (detaching && td_ta_clear_event_p != NULL)
{
td_thr_events_t events;
- /* Set the process wide mask saying we aren't interested in any
- events anymore. */
+ /* Set the process wide mask saying we aren't interested
+ in any events anymore. */
td_event_fillset (&events);
(*td_ta_clear_event_p) (thread_db->thread_agent, &events);
}
- td_ta_delete_p = dlsym (thread_db->handle, "td_ta_delete");
if (td_ta_delete_p != NULL)
(*td_ta_delete_p) (thread_db->thread_agent);
+#ifndef USE_LIBTHREAD_DB_DIRECTLY
dlclose (thread_db->handle);
-#else
- td_thr_events_t events;
-
- td_event_fillset (&events);
- td_ta_clear_event (thread_db->thread_agent, &events);
- td_ta_delete (thread_db->thread_agent);
#endif /* USE_LIBTHREAD_DB_DIRECTLY */
free (thread_db);