Index: gdb-7.99.90.20170420/gdb/infrun.c

===================================================================

--- gdb-7.99.90.20170420.orig/gdb/infrun.c	2017-04-20 23:19:16.056434309 +0200

+++ gdb-7.99.90.20170420/gdb/infrun.c	2017-04-20 23:19:22.932480367 +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-7.99.90.20170420/gdb/linux-nat.c

===================================================================

--- gdb-7.99.90.20170420.orig/gdb/linux-nat.c	2017-04-20 23:19:16.058434322 +0200

+++ gdb-7.99.90.20170420/gdb/linux-nat.c	2017-04-20 23:19:22.933480373 +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 *);

@@ -1055,6 +1060,9 @@

       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 /

@@ -1412,6 +1420,25 @@

       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;

 }

@@ -1570,6 +1597,10 @@

       detach_one_lwp (main_lwp, &signo);

       inf_ptrace_detach_success (ops);

+

+#ifdef NEED_DETACH_SIGSTOP

+      pid_was_stopped = 0;

+#endif

     }

 }

@@ -1830,6 +1861,16 @@

       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);

@@ -3826,6 +3867,10 @@

   /* 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-7.99.90.20170420/gdb/testsuite/gdb.threads/attach-stopped.exp

===================================================================

--- gdb-7.99.90.20170420.orig/gdb/testsuite/gdb.threads/attach-stopped.exp	2017-04-20 23:19:16.059434329 +0200

+++ gdb-7.99.90.20170420/gdb/testsuite/gdb.threads/attach-stopped.exp	2017-04-20 23:19:22.933480373 +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" {