Add "maint info linux-lwps" command

This adds a maintenance command that lets you list all the LWPs under
control of the linux-nat target.

For example:

 (gdb) maint info linux-lwps
 LWP Ptid        Thread ID
 560948.561047.0 None
 560948.560948.0 1.1

This shows that "560948.561047.0" LWP doesn't map to any thread_info
object, which is bogus.  We'll be using this in a testcase in a
following patch.

Co-Authored-By: Pedro Alves <pedro@palves.net>
Change-Id: Ic4e9e123385976e5cd054391990124b7a20fb3f5

3 files changed, 55 insertions, 0 deletions

diff --git a/gdb/NEWS b/gdb/NEWS
index 3851114..d85a13b 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -24,6 +24,11 @@ disassemble
   ** New read/write attribute gdb.Value.bytes that contains a bytes
      object holding the contents of this value.
 
+* New commands
+
+maintenance info linux-lwps
+  List all LWPs under control of the linux-nat target.
+
 *** Changes in GDB 14
 
 * GDB now supports the AArch64 Scalable Matrix Extension 2 (SME2), which
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 2cd565e..4cbaaa6 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -41189,6 +41189,10 @@ module (@pxref{Disassembly In Python}), and will only be present after
 that module has been imported.  To force the module to be imported do
 the following:
 
+@kindex maint info linux-lwps
+@item maint info linux-lwps
+Print information about LWPs under control of the Linux native target.
+
 @smallexample
 (@value{GDBP}) python import gdb.disassembler
 @end smallexample
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 1c9756c..f73e52f 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -4503,6 +4503,49 @@ current_lwp_ptid (void)
   return inferior_ptid;
 }
 
+/* Implement 'maintenance info linux-lwps'.  Displays some basic
+   information about all the current lwp_info objects.  */
+
+static void
+maintenance_info_lwps (const char *arg, int from_tty)
+{
+  if (all_lwps ().size () == 0)
+    {
+      gdb_printf ("No Linux LWPs\n");
+      return;
+    }
+
+  /* Start the width at 8 to match the column heading below, then
+     figure out the widest ptid string.  We'll use this to build our
+     output table below.  */
+  size_t ptid_width = 8;
+  for (lwp_info *lp : all_lwps ())
+    ptid_width = std::max (ptid_width, lp->ptid.to_string ().size ());
+
+  /* Setup the table headers.  */
+  struct ui_out *uiout = current_uiout;
+  ui_out_emit_table table_emitter (uiout, 2, -1, "linux-lwps");
+  uiout->table_header (ptid_width, ui_left, "lwp-ptid", _("LWP Ptid"));
+  uiout->table_header (9, ui_left, "thread-info", _("Thread ID"));
+  uiout->table_body ();
+
+  /* Display one table row for each lwp_info.  */
+  for (lwp_info *lp : all_lwps ())
+    {
+      ui_out_emit_tuple tuple_emitter (uiout, "lwp-entry");
+
+      thread_info *th = linux_target->find_thread (lp->ptid);
+
+      uiout->field_string ("lwp-ptid", lp->ptid.to_string ().c_str ());
+      if (th == nullptr)
+	uiout->field_string ("thread-info", "None");
+      else
+	uiout->field_string ("thread-info", print_full_thread_id (th));
+
+      uiout->message ("\n");
+    }
+}
+
 void _initialize_linux_nat ();
 void
 _initialize_linux_nat ()
@@ -4540,6 +4583,9 @@ Enables printf debugging output."),
   sigemptyset (&blocked_mask);
 
   lwp_lwpid_htab_create ();
+
+  add_cmd ("linux-lwps", class_maintenance, maintenance_info_lwps,
+	 _("List the Linux LWPS."), &maintenanceinfolist);
 }