[PATCH][PR threads/15824] when get threads name failed from info threads with linux kernel version earlier than 2.6.33

["Will Huang" <will.huang@aliyun-inc.com>]

Test OS:Linux  2.6.32-220.23.2.ali1089.el5.x86_64 
GNU gdb (GDB) 7.6

Under linux kernel 2.6.32( or earlier version) there is no proc file named
/proc/$pid/task/$tid/comm. 
GDB init their threads' name from this proc file. So info threads can't
print correct thread names when 
This proc file not exist. This can be solve by using procfs
/proc/$pid/task/$tid/status instead if comm file 
not exists. Status file has a Name line which starts by "Name:".

diff -ruN ./gdb.org/ChangeLog ./gdb/ChangeLog
--- ./gdb.org/ChangeLog 2013-04-26 19:43:30.000000000 +0800
+++ ./gdb/ChangeLog     2013-08-14 11:09:08.000000000 +0800
@@ -1,3 +1,11 @@
+2013-08-14  Will Huang  <will.huang@aliyun-inc.com>
+
+       PR threads/15824
+       * linux-nat.c (linux_nat_thread_name): Add get thread name from
+       procfs "/proc/$pid/task/$tid/status".
+       * commo/linux-procfs.c (linux_proc_get_thread_name): New.
+       * commo/linux-procfs.c (linux_proc_get_string): New.
+
 2013-04-26  Joel Brobecker  <brobecker@adacore.com>

        * NEWS: Change "since GDB 7.5" into "in GDB 7.6".
diff -ruN ./gdb.org/common/linux-procfs.c ./gdb/common/linux-procfs.c
--- ./gdb.org/common/linux-procfs.c     2013-01-01 14:32:54.000000000 +0800
+++ ./gdb/common/linux-procfs.c 2013-08-12 16:51:33.000000000 +0800
@@ -55,6 +55,51 @@
   return retval;
 }

+/* Return the string length of Name from /proc/$pid/task/$tid/status.
+   Returns -1 if not found.  */
+
+static int
+linux_proc_get_string (pid_t lwpid, pid_t tid,
+                       char *target, size_t t_size, const char *field)
+{
+  size_t field_len = strlen (field);
+  FILE *status_file;
+  char buf[100];
+  int retval = -1;
+
+  if (tid > 0)
+       snprintf (buf, sizeof (buf),
+                  "/proc/%d/task/%d/status", (int) lwpid, (int) tid);
+  else
+       snprintf (buf, sizeof (buf), "/proc/%d/status", (int) lwpid);
+
+  status_file = fopen (buf, "r");
+  if (status_file == NULL)
+    {
+      warning (_("unable to open /proc file '%s'"), buf);
+      return -1;
+    }
+
+  while (fgets (buf, sizeof (buf), status_file))
+    if (strncmp (buf, field, field_len) == 0 && buf[field_len] == ':')
+      {
+       size_t pos = field_len + 1;
+       while((buf[pos] == ' ' || buf[pos] == '\t') && (pos < sizeof (buf) -
1))
+         pos++;
+
+       strncpy (target, &buf[pos], t_size);
+       target[t_size - 1] = '\0';
+       retval = strlen (target);
+       if(retval > 0 && target[retval - 1] == '\n')
+               target[retval - 1] = '\0';
+
+       break;
+      }
+
+  fclose (status_file);
+  return retval;
+}
+
 /* Return the TGID of LWPID from /proc/pid/status.  Returns -1 if not
    found.  */

@@ -118,3 +163,11 @@
 {
   return linux_proc_pid_has_state (pid, "Z (zombie)");
 }
+
+/*Get thread name identified by PID & TID*/
+
+int
+linux_proc_get_thread_name (pid_t pid, pid_t tid, char *name, size_t size)
+{
+  return linux_proc_get_string (pid, tid, name, size, "Name");
+}
diff -ruN ./gdb.org/common/linux-procfs.h ./gdb/common/linux-procfs.h
--- ./gdb.org/common/linux-procfs.h     2013-01-01 14:32:54.000000000 +0800
+++ ./gdb/common/linux-procfs.h 2013-08-12 16:50:39.000000000 +0800
@@ -40,4 +40,10 @@

 extern int linux_proc_pid_is_zombie (pid_t pid);

+/* Return -1 if thread Name of tid didn't found;
+   "char *name" for thread name (need be allocated by caller).  */
+
+extern int linux_proc_get_thread_name (pid_t pid, pid_t tid,
+                                       char *name, size_t size);
+
 #endif /* COMMON_LINUX_PROCFS_H */
diff -ruN ./gdb.org/linux-nat.c ./gdb/linux-nat.c
--- ./gdb.org/linux-nat.c       2013-02-13 22:59:49.000000000 +0800
+++ ./gdb/linux-nat.c   2013-08-12 16:47:26.000000000 +0800
@@ -4294,6 +4294,14 @@

       fclose (comm_file);
     }
+    else
+    {
+      static char comm[COMM_LEN + 1];
+      int size = linux_proc_get_thread_name (pid, lwp, comm, COMM_LEN+1);
+      if (size > 0)
+        result = comm;
+
+    }

 #undef COMM_LEN
 #undef FORMAT
diff -ruN ./gdb.org/testsuite/ChangeLog ./gdb/testsuite/ChangeLog
--- ./gdb.org/testsuite/ChangeLog       2013-04-25 20:22:26.000000000 +0800
+++ ./gdb/testsuite/ChangeLog   2013-08-14 12:18:23.000000000 +0800
@@ -1,3 +1,9 @@
+2013-08-14  Will Huang  <will.huang@aliyun-inc.com>
+
+       PR threads/15824
+       * gdb.threads/manythreads.exp: Add test for get thread
+       original name
+
 2013-04-25  Sergio Durigan Junior  <sergiodj@redhat.com>

        * gdb.arch/arm-bl-branch-dest.c: New file.
diff -ruN ./gdb.org/testsuite/gdb.threads/manythreads.exp
./gdb/testsuite/gdb.threads/manythreads.exp
--- ./gdb.org/testsuite/gdb.threads/manythreads.exp     2013-01-01
14:41:27.000000000 +0800
+++ ./gdb/testsuite/gdb.threads/manythreads.exp 2013-08-14
12:15:07.000000000 +0800
@@ -93,6 +93,7 @@
     }
 }

+gdb_test "info threads" ".*manythreads.*" "check thread original name"
 gdb_test_no_output "thread name zardoz" "give a name to the thread"
 gdb_test "info threads" ".*zardoz.*" "check thread name"



Thanks,
Will Huang