On 05/09/2016 12:18 AM, Baoquan He wrote:
Hi Corey,

I am trying to review this patch now, and these fixes contained are very
great. Just several concerns are added in inline comment.

By the way, did you run this in your side?

Yes, I tested on x86, x86_64, ARM and MIPS.

Comments inline...


Hi Vivek,

Member variable was added into task_struct in below commit replacing
pids[PIDTYPE_TGID], and from then on nobody complained about it. Seems
people rarely use this utility.

commit 47e65328a7b1cdfc4e3102e50d60faf94ebba7d3
Author: Oleg Nesterov <o...@tv-sign.ru>
Date:   Tue Mar 28 16:11:25 2006 -0800

     [PATCH] pids: kill PIDTYPE_TGID



On 04/27/16 at 07:21am, Corey Minyard wrote:
Any comments on this?  If no one else cares I'd be willing to take over
maintenance of this.

-corey

On 02/25/2016 07:51 AM, miny...@acm.org wrote:
From: Corey Minyard <cminy...@mvista.com>

Lots of little changes needed to be made to clean these up, remove the
four byte pointer assumption and traverse the pid queue properly.
Also consolidate the traceback code into a single function instead
of having three copies of it.

Signed-off-by: Corey Minyard <cminy...@mvista.com>
---
  Documentation/kdump/gdbmacros.txt | 90 +++++++++++++++++----------------------
  1 file changed, 40 insertions(+), 50 deletions(-)

I sent this earlier, but I didn't get a response.  These are clearly
wrong.  I'd be happy to take over maintenance of these macros.  It
might be better to move them someplace else, too, since they are also
useful for kgdb.

diff --git a/Documentation/kdump/gdbmacros.txt 
b/Documentation/kdump/gdbmacros.txt
index 9b9b454..e5bbd8d 100644
--- a/Documentation/kdump/gdbmacros.txt
+++ b/Documentation/kdump/gdbmacros.txt
@@ -15,14 +15,14 @@
  define bttnobp
        set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
-       set $pid_off=((size_t)&((struct task_struct *)0)->pids[1].pid_list.next)
+       set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
This is a quite nice fix.

        set $init_t=&init_task
        set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
        while ($next_t != $init_t)
                set $next_t=(struct task_struct *)$next_t
                printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
                printf "===================\n"
-               set var $stackp = $next_t.thread.esp
+               set var $stackp = $next_t.thread.sp
                set var $stack_top = ($stackp & ~4095) + 4096
                while ($stackp < $stack_top)
@@ -31,12 +31,12 @@ define bttnobp
                        end
                        set $stackp += 4
                end
-               set $next_th=(((char *)$next_t->pids[1].pid_list.next) - 
$pid_off)
+               set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
                while ($next_th != $next_t)
                        set $next_th=(struct task_struct *)$next_th
                        printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
                        printf "===================\n"
-                       set var $stackp = $next_t.thread.esp
+                       set var $stackp = $next_t.thread.sp
                        set var $stack_top = ($stackp & ~4095) + 4096
                        while ($stackp < $stack_top)
@@ -45,7 +45,7 @@ define bttnobp
                                end
                                set $stackp += 4
                        end
-                       set $next_th=(((char *)$next_th->pids[1].pid_list.next) 
- $pid_off)
+                       set $next_th=(((char *)$next_th->thread_group.next) - 
$pid_off)
                end
                set $next_t=(char *)($next_t->tasks.next) - $tasks_off
        end
@@ -54,42 +54,43 @@ document bttnobp
        dump all thread stack traces on a kernel compiled with 
!CONFIG_FRAME_POINTER
  end
+define btthreadstruct
This is a nice wrapping, but I guess you want to name it as
btthreadstack, right? Since I didn't get at all why it's related to
thread_struct except of getting 'sp'.


The name is based on what is passed into the function. You do a backtrace when given a thread structure. In my experience it is best to name functions based upon how the function's user sees it. Though I'm not stuck on the name, if you would prefer btthreadstack.

+       set var $pid_task = $arg0
+
+       printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
+       printf "task struct: "
+       print $pid_task
+       printf "===================\n"
+       set var $stackp = $pid_task.thread.sp
+       set var $stack_top = ($stackp & ~4095) + 4096
+       set var $stack_bot = ($stackp & ~4095)
+
+       set $stackp = *((unsigned long *) $stackp)
+       while (($stackp < $stack_top) && ($stackp > $stack_bot))
+               set var $addr = *(((unsigned long *) $stackp) + 1)
+               info symbol $addr
+               set $stackp = *((unsigned long *) $stackp)
+       end
+end
+document btthreadstruct
+        dump a thread stack using the given task structure pointer
+end
+
+
  define btt
        set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
-       set $pid_off=((size_t)&((struct task_struct *)0)->pids[1].pid_list.next)
+       set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
        set $init_t=&init_task
        set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
        while ($next_t != $init_t)
                set $next_t=(struct task_struct *)$next_t
-               printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
-               printf "===================\n"
-               set var $stackp = $next_t.thread.esp
-               set var $stack_top = ($stackp & ~4095) + 4096
-               set var $stack_bot = ($stackp & ~4095)
+               btthreadstruct $next_t
-               set $stackp = *($stackp)
-               while (($stackp < $stack_top) && ($stackp > $stack_bot))
-                       set var $addr = *($stackp + 4)
-                       info symbol $addr
-                       set $stackp = *($stackp)
-               end
-
-               set $next_th=(((char *)$next_t->pids[1].pid_list.next) - 
$pid_off)
+               set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
                while ($next_th != $next_t)
                        set $next_th=(struct task_struct *)$next_th
-                       printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
-                       printf "===================\n"
-                       set var $stackp = $next_t.thread.esp
-                       set var $stack_top = ($stackp & ~4095) + 4096
-                       set var $stack_bot = ($stackp & ~4095)
-
-                       set $stackp = *($stackp)
-                       while (($stackp < $stack_top) && ($stackp > $stack_bot))
-                               set var $addr = *($stackp + 4)
-                               info symbol $addr
-                               set $stackp = *($stackp)
-                       end
-                       set $next_th=(((char *)$next_th->pids[1].pid_list.next) 
- $pid_off)
+                       btthreadstruct $next_th
+                       set $next_th=(((char *)$next_th->thread_group.next) - 
$pid_off)
                end
                set $next_t=(char *)($next_t->tasks.next) - $tasks_off
        end
@@ -101,7 +102,7 @@ end
  define btpid
        set var $pid = $arg0
        set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
-       set $pid_off=((size_t)&((struct task_struct *)0)->pids[1].pid_list.next)
+       set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
        set $init_t=&init_task
        set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
        set var $pid_task = 0
@@ -113,29 +114,18 @@ define btpid
                        set $pid_task = $next_t
                end
-               set $next_th=(((char *)$next_t->pids[1].pid_list.next) - 
$pid_off)
+               set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
                while ($next_th != $next_t)
                        set $next_th=(struct task_struct *)$next_th
                        if ($next_th.pid == $pid)
                                set $pid_task = $next_th
                        end
-                       set $next_th=(((char *)$next_th->pids[1].pid_list.next) 
- $pid_off)
+                       set $next_th=(((char *)$next_th->thread_group.next) - 
$pid_off)
                end
                set $next_t=(char *)($next_t->tasks.next) - $tasks_off
        end
-       printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
-       printf "===================\n"
-       set var $stackp = $pid_task.thread.esp
-       set var $stack_top = ($stackp & ~4095) + 4096
-       set var $stack_bot = ($stackp & ~4095)
-
-       set $stackp = *($stackp)
-       while (($stackp < $stack_top) && ($stackp > $stack_bot))
-               set var $addr = *($stackp + 4)
-               info symbol $addr
-               set $stackp = *($stackp)
-       end
+       btthreadstruct $pid_task
  end
  document btpid
        backtrace of pid
@@ -145,7 +135,7 @@ end
  define trapinfo
        set var $pid = $arg0
        set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
-       set $pid_off=((size_t)&((struct task_struct *)0)->pids[1].pid_list.next)
+       set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
        set $init_t=&init_task
        set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
        set var $pid_task = 0
@@ -157,13 +147,13 @@ define trapinfo
                        set $pid_task = $next_t
                end
-               set $next_th=(((char *)$next_t->pids[1].pid_list.next) - 
$pid_off)
+               set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
                while ($next_th != $next_t)
                        set $next_th=(struct task_struct *)$next_th
                        if ($next_th.pid == $pid)
                                set $pid_task = $next_th
                        end
-                       set $next_th=(((char *)$next_th->pids[1].pid_list.next) 
- $pid_off)
+                       set $next_th=(((char *)$next_th->thread_group.next) - 
$pid_off)
                end
                set $next_t=(char *)($next_t->tasks.next) - $tasks_off
        end

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