[PATCH] libdwfl: linux-pid-attach.c: Report actual PID (Tgid) to dwfl_attach_state.

[Mark Wielaard]

Signed-off-by: Mark Wielaard <m...@redhat.com>
---
 libdwfl/ChangeLog          |    5 +++++
 libdwfl/linux-pid-attach.c |   21 +++++++++++++++++++++
 src/ChangeLog              |    4 ++++
 src/stack.c                |    2 ++
 4 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 723ea71..8a164f0 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,8 @@
+2013-12-23  Mark Wielaard  <m...@redhat.com>
+
+       * linux-pid-attach.c (__libdwfl_attach_state_for_pid): Report actual
+       pid (thread group leader) to dwfl_attach_state.
+
 2013-12-21  Mark Wielaard  <m...@redhat.com>
 
        * linux-pid-attach.c (struct pid_arg): New field should_detach.
diff --git a/libdwfl/linux-pid-attach.c b/libdwfl/linux-pid-attach.c
index 1e1ccfa..232a3de 100644
--- a/libdwfl/linux-pid-attach.c
+++ b/libdwfl/linux-pid-attach.c
@@ -301,6 +301,27 @@ bool
 internal_function
 __libdwfl_attach_state_for_pid (Dwfl *dwfl, pid_t pid)
 {
+  char buffer[36];
+  FILE *procfile;
+
+  /* Make sure to report the actual PID (thread group leader) to
+     dwfl_attach_state.  */
+  snprintf (buffer, sizeof (buffer), "/proc/%ld/status", (long) pid);
+  procfile = fopen (buffer, "r");
+  if (procfile == NULL)
+    return false;
+
+  while (fgets (buffer, sizeof (buffer), procfile) != NULL)
+    if (strncmp (buffer, "Tgid:", 5) == 0)
+      {
+        pid = atoi (&buffer[5]);
+        break;
+      }
+  fclose (procfile);
+
+  if (pid == 0)
+    return false;
+
   char dirname[64];
   int i = snprintf (dirname, sizeof (dirname), "/proc/%ld/task", (long) pid);
   assert (i > 0 && i < (ssize_t) sizeof (dirname) - 1);
diff --git a/src/ChangeLog b/src/ChangeLog
index ea30556..0f1b971 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,9 @@
 2013-12-23  Mark Wielaard  <m...@redhat.com>
 
+       * stack.c (main): Print pid of process or core.
+
+2013-12-23  Mark Wielaard  <m...@redhat.com>
+
        * stack.c (OPT_DEBUGINFO): New define.
        (OPT_COREFILE): Likewise.
        (pid): New static.
diff --git a/src/stack.c b/src/stack.c
index 3b0d767..dfb0272 100644
--- a/src/stack.c
+++ b/src/stack.c
@@ -376,6 +376,7 @@ main (int argc, char **argv)
 
   if (show_one_tid)
     {
+      printf ("TID %d:\n", pid);
       switch (dwfl_getthread_frames (dwfl, pid, frame_callback, frames))
        {
        case DWARF_CB_OK:
@@ -391,6 +392,7 @@ main (int argc, char **argv)
     }
   else
     {
+      printf ("PID %d - %s\n", dwfl_pid (dwfl), pid != 0 ? "process" : "core");
       switch (dwfl_getthreads (dwfl, thread_callback, frames))
        {
        case DWARF_CB_OK:
-- 
1.7.1