Index: gdb-7.11.50.20160716/gdb/infrun.c
===================================================================
--- gdb-7.11.50.20160716.orig/gdb/infrun.c	2016-07-16 14:37:09.317178150 +0200
+++ gdb-7.11.50.20160716/gdb/infrun.c	2016-07-16 14:37:10.636188765 +0200
@@ -620,6 +620,13 @@
 				target_pid_to_str (process_ptid));
 	    }
 
+#ifdef NEED_DETACH_SIGSTOP
+	  /* We should check PID_WAS_STOPPED and detach it stopped accordingly.
+	     In this point of code it cannot be 1 as we would not get FORK
+	     executed without CONTINUE first which resets PID_WAS_STOPPED.
+	     We would have to first TARGET_STOP and WAITPID it as with running
+	     inferior PTRACE_DETACH, SIGSTOP will ignore the signal.  */
+#endif
 	  target_detach (NULL, 0);
 	}
 
Index: gdb-7.11.50.20160716/gdb/linux-nat.c
===================================================================
--- gdb-7.11.50.20160716.orig/gdb/linux-nat.c	2016-07-16 14:37:09.320178174 +0200
+++ gdb-7.11.50.20160716/gdb/linux-nat.c	2016-07-16 14:38:09.574663094 +0200
@@ -194,6 +194,11 @@
 static struct target_ops *linux_ops;
 static struct target_ops linux_ops_saved;
 
+#ifdef NEED_DETACH_SIGSTOP
+/* PID of the inferior stopped by SIGSTOP before attaching (or zero).  */
+static pid_t pid_was_stopped;
+
+#endif
 /* The method to call, if any, when a new thread is attached.  */
 static void (*linux_nat_new_thread) (struct lwp_info *);
 
@@ -1047,6 +1052,9 @@
       if (debug_linux_nat)
 	fprintf_unfiltered (gdb_stdlog,
 			    "LNPAW: Attaching to a stopped process\n");
+#ifdef NEED_DETACH_SIGSTOP
+      pid_was_stopped = ptid_get_pid (ptid);
+#endif
 
       /* The process is definitely stopped.  It is in a job control
 	 stop, unless the kernel predates the TASK_STOPPED /
@@ -1404,6 +1412,25 @@
       return gdb_signal_to_host (signo);
     }
 
+#ifdef NEED_DETACH_SIGSTOP
+  /* Workaround RHEL-5 kernel which has unreliable PTRACE_DETACH, SIGSTOP (that
+     many TIDs are left unstopped).  See RH Bug 496732.  */
+  if (ptid_get_pid (lp->ptid) == pid_was_stopped)
+    {
+      int err;
+
+      errno = 0;
+      err = kill_lwp (ptid_get_lwp (lp->ptid), SIGSTOP);
+      if (debug_linux_nat)
+	{
+	  fprintf_unfiltered (gdb_stdlog,
+			      "SC:  lwp kill %d %s\n",
+			      err,
+			      errno ? safe_strerror (errno) : "ERRNO-OK");
+	}
+    }
+
+#endif
   return 0;
 }
 
@@ -1562,6 +1589,10 @@
       detach_one_lwp (main_lwp, &signo);
 
       inf_ptrace_detach_success (ops);
+
+#ifdef NEED_DETACH_SIGSTOP
+      pid_was_stopped = 0;
+#endif
     }
   delete_lwp (main_lwp->ptid);
 }
@@ -1823,6 +1854,16 @@
       return;
     }
 
+#ifdef NEED_DETACH_SIGSTOP
+  /* At this point, we are going to resume the inferior and if we
+     have attached to a stopped process, we no longer should leave
+     it as stopped if the user detaches.  PTID variable has PID set to LWP
+     while we need to check the real PID here.  */
+
+  if (!step && lp && pid_was_stopped == ptid_get_pid (lp->ptid))
+    pid_was_stopped = 0;
+
+#endif
   if (resume_many)
     iterate_over_lwps (ptid, linux_nat_resume_callback, lp);
 
@@ -3819,6 +3860,10 @@
 
   /* Let the arch-specific native code know this process is gone.  */
   linux_nat_forget_process (pid);
+#ifdef NEED_DETACH_SIGSTOP
+
+  pid_was_stopped = 0;
+#endif
 }
 
 /* Convert a native/host siginfo object, into/from the siginfo in the
Index: gdb-7.11.50.20160716/gdb/testsuite/gdb.threads/attach-stopped.exp
===================================================================
--- gdb-7.11.50.20160716.orig/gdb/testsuite/gdb.threads/attach-stopped.exp	2016-07-16 14:37:09.321178182 +0200
+++ gdb-7.11.50.20160716/gdb/testsuite/gdb.threads/attach-stopped.exp	2016-07-16 14:37:10.640188797 +0200
@@ -56,7 +56,65 @@
     gdb_reinitialize_dir $srcdir/$subdir
     gdb_load ${binfile}
 
-    # Verify that we can attach to the stopped process.
+    # Verify that we can attach to the process by first giving its
+    # executable name via the file command, and using attach with the
+    # process ID.
+
+    set test "$threadtype: set file, before attach1 to stopped process"
+    gdb_test_multiple "file $binfile" "$test" {
+       -re "Load new symbol table from.*y or n. $" {
+	    gdb_test "y" "Reading symbols from $escapedbinfile\.\.\.*done." \
+		    "$test (re-read)"
+	}
+	-re "Reading symbols from $escapedbinfile\.\.\.*done.*$gdb_prompt $" {
+	    pass "$test"
+	}
+    }
+
+    set test "$threadtype: attach1 to stopped, after setting file"
+    gdb_test_multiple "attach $testpid" "$test" {
+	-re "Attaching to program.*`?$escapedbinfile'?, process $testpid.*$gdb_prompt $" {
+	    pass "$test"
+	}
+    }
+
+    # ".*sleep.*clone.*" would fail on s390x as bt stops at START_THREAD there.
+    if {[string equal $threadtype threaded]} {
+	gdb_test "thread apply all bt" ".*sleep.*start_thread.*" "$threadtype: attach1 to stopped bt"
+    } else {
+	gdb_test "bt" ".*sleep.*main.*" "$threadtype: attach1 to stopped bt"
+    }
+
+    # Exit and detach the process.
+       
+    gdb_exit
+
+    # Avoid some race:
+    sleep 2
+
+    if [catch {open /proc/${testpid}/status r} fileid] {
+	set line2 "NOTFOUND"
+    } else {
+	gets $fileid line1;
+	gets $fileid line2;
+	close $fileid;
+    }
+
+    set test "$threadtype: attach1, exit leaves process stopped"
+    if {[string match "*(stopped)*" $line2]} {
+      pass $test
+    } else {
+      fail $test
+    }
+
+    # At this point, the process should still be stopped
+
+    gdb_start
+    gdb_reinitialize_dir $srcdir/$subdir
+    gdb_load ${binfile}
+
+    # Verify that we can attach to the process just by giving the
+    # process ID.
        
     set test "$threadtype: attach2 to stopped, after setting file"
     gdb_test_multiple "attach $testpid" "$test" {