gdb/gdb-6.6-bz247354-leader-exit-fix.patch

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2007-07-08 Jan Kratochvil <jan.kratochvil@redhat.com>
* linux-nat.c (linux_lwp_is_zombie): New function.
(wait_lwp): Fix lockup on exit of the thread group leader.
(linux_xfer_partial): Renamed to ...
(linux_xfer_partial_lwp): ... here.
(linux_xfer_partial): New function wrapping LINUX_XFER_PARTIAL_LWP.
--- ./gdb/linux-nat.c 3 Jul 2007 17:01:55 -0000 1.65
+++ ./gdb/linux-nat.c 7 Jul 2007 15:21:57 -0000
@@ -1343,6 +1343,31 @@ linux_handle_extended_wait (struct lwp_i
_("unknown ptrace event %d"), event);
}
+static int
+linux_lwp_is_zombie (long lwp)
+{
+ char buffer[MAXPATHLEN];
+ FILE *procfile;
+ int retval = 0;
+
+ sprintf (buffer, "/proc/%ld/status", lwp);
+ procfile = fopen (buffer, "r");
+ if (procfile == NULL)
+ {
+ warning (_("unable to open /proc file '%s'"), buffer);
+ return 0;
+ }
+ while (fgets (buffer, sizeof (buffer), procfile) != NULL)
+ if (strcmp (buffer, "State:\tZ (zombie)\n") == 0)
+ {
+ retval = 1;
+ break;
+ }
+ fclose (procfile);
+
+ return retval;
+}
+
/* Wait for LP to stop. Returns the wait status, or 0 if the LWP has
exited. */
@@ -1350,16 +1375,31 @@ static int
wait_lwp (struct lwp_info *lp)
{
pid_t pid;
- int status;
+ int status = 0;
int thread_dead = 0;
gdb_assert (!lp->stopped);
gdb_assert (lp->status == 0);
- pid = my_waitpid (GET_LWP (lp->ptid), &status, 0);
- if (pid == -1 && errno == ECHILD)
+ /* Thread group leader may have exited but we would lock up by WAITPID as it
+ waits on all its threads; __WCLONE is not applicable for the leader.
+ The thread leader restrictions is only a performance optimization here.
+ LINUX_NAT_THREAD_ALIVE cannot be used here as it requires a STOPPED
+ process; it gets ESRCH both for the zombie and for running processes. */
+ if (is_lwp (lp->ptid) && GET_PID (lp->ptid) == GET_LWP (lp->ptid)
+ && linux_lwp_is_zombie (GET_LWP (lp->ptid)))
+ {
+ thread_dead = 1;
+ if (debug_linux_nat)
+ fprintf_unfiltered (gdb_stdlog, "WL: Threads leader %s vanished.\n",
+ target_pid_to_str (lp->ptid));
+ }
+
+ if (!thread_dead)
{
- pid = my_waitpid (GET_LWP (lp->ptid), &status, __WCLONE);
+ pid = my_waitpid (GET_LWP (lp->ptid), &status, 0);
+ if (pid == -1 && errno == ECHILD)
+ pid = my_waitpid (GET_LWP (lp->ptid), &status, __WCLONE);
if (pid == -1 && errno == ECHILD)
{
/* The thread has previously exited. We need to delete it
@@ -3144,10 +3159,12 @@ linux_proc_pending_signals (int pid, sig
fclose (procfile);
}
+/* Transfer from the specific LWP currently set by PID of INFERIOR_PTID. */
+
static LONGEST
-linux_xfer_partial (struct target_ops *ops, enum target_object object,
- const char *annex, gdb_byte *readbuf,
- const gdb_byte *writebuf, ULONGEST offset, LONGEST len)
+linux_xfer_partial_lwp (struct target_ops *ops, enum target_object object,
+ const char *annex, gdb_byte *readbuf,
+ const gdb_byte *writebuf, ULONGEST offset, LONGEST len)
{
LONGEST xfer;
@@ -3164,6 +3181,45 @@ linux_xfer_partial (struct target_ops *o
offset, len);
}
+/* nptl_db expects being able to transfer memory just by specifying PID.
+ After the thread group leader exists the Linux kernel turns the task
+ into zombie no longer permitting accesses to its memory.
+ Transfer the memory from an arbitrary LWP_LIST entry in such case. */
+
+static LONGEST
+linux_xfer_partial (struct target_ops *ops, enum target_object object,
+ const char *annex, gdb_byte *readbuf,
+ const gdb_byte *writebuf, ULONGEST offset, LONGEST len)
+{
+ LONGEST xfer;
+ struct lwp_info *lp;
+ /* Not using SAVE_INFERIOR_PTID already here for better performance. */
+ struct cleanup *old_chain = NULL;
+ ptid_t inferior_ptid_orig = inferior_ptid;
+
+ errno = 0;
+ xfer = linux_xfer_partial_lwp (ops, object, annex, readbuf, writebuf,
+ offset, len);
+
+ for (lp = lwp_list; xfer == 0 && (errno == EACCES || errno == ESRCH)
+ && lp != NULL; lp = lp->next)
+ {
+ if (!is_lwp (lp->ptid) || ptid_equal (lp->ptid, inferior_ptid_orig))
+ continue;
+
+ if (old_chain == NULL)
+ old_chain = save_inferior_ptid ();
+ inferior_ptid = BUILD_LWP (GET_LWP (lp->ptid), GET_LWP (lp->ptid));
+ errno = 0;
+ xfer = linux_xfer_partial_lwp (ops, object, annex, readbuf, writebuf,
+ offset, len);
+ }
+
+ if (old_chain != NULL)
+ do_cleanups (old_chain);
+ return xfer;
+}
+
/* Create a prototype generic Linux target. The client can override
it with local methods. */