Since commit 8e1f385104ac ("kill task_struct->thread_group") remove
the thread_group, we will encounter below issue.

(gdb) lx-ps
      TASK          PID    COMM
0xffff800086503340   0   swapper/0
Python Exception <class 'gdb.error'>: There is no member named thread_group.
Error occurred in Python: There is no member named thread_group.

We use signal->thread_head to iterate all threads instead.

Fixes: 8e1f385104ac ("kill task_struct->thread_group")
Cc: stable@vger.kernel.org
Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
---
 scripts/gdb/linux/tasks.py | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/scripts/gdb/linux/tasks.py b/scripts/gdb/linux/tasks.py
index 17ec19e9b5bf..7c32f4c8284b 100644
--- a/scripts/gdb/linux/tasks.py
+++ b/scripts/gdb/linux/tasks.py
@@ -13,7 +13,7 @@
 
 import gdb
 
-from linux import utils
+from linux import utils, lists
 
 
 task_type = utils.CachedType("struct task_struct")
@@ -25,13 +25,9 @@ def task_lists():
     t = g = init_task
 
     while True:
-        while True:
-            yield t
-
-            t = utils.container_of(t['thread_group']['next'],
-                                   task_ptr_type, "thread_group")
-            if t == g:
-                break
+        thread_head = t['signal']['thread_head']
+        for thread in lists.list_for_each_entry(thread_head, task_ptr_type, 'thread_node'):
+            yield thread
 
         t = g = utils.container_of(g['tasks']['next'],
                                    task_ptr_type, "tasks")
-- 
2.18.0

On 11/27, Kuan-Ying Lee wrote:
>
> @@ -25,13 +25,9 @@ def task_lists():
>      t = g = init_task
>  
>      while True:
> -        while True:
> -            yield t
> -
> -            t = utils.container_of(t['thread_group']['next'],
> -                                   task_ptr_type, "thread_group")
> -            if t == g:
> -                break
> +        thread_head = t['signal']['thread_head']
> +        for thread in lists.list_for_each_entry(thread_head, task_ptr_type, 'thread_node'):
> +            yield thread
>  
>          t = g = utils.container_of(g['tasks']['next'],
>                                     task_ptr_type, "tasks")

Thanks!

I do not know python, but it seems that with this patch we can kill g or t?
Can't

	def task_lists():
	    task_ptr_type = task_type.get_type().pointer()
	    init_task = gdb.parse_and_eval("init_task").address
	    t = init_task

	    while True:
		thread_head = t['signal']['thread_head']
		for thread in lists.list_for_each_entry(thread_head, task_ptr_type, 'thread_node'):
		    yield thread

		t = utils.container_of(t['tasks']['next'],
				       task_ptr_type, "tasks")
		if t == init_task:
		    return

work?

Oleg.

On Mon, 2023-11-27 at 13:03 +0100, Oleg Nesterov wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  On 11/27, Kuan-Ying Lee wrote:
> >
> > @@ -25,13 +25,9 @@ def task_lists():
> >      t = g = init_task
> >  
> >      while True:
> > -        while True:
> > -            yield t
> > -
> > -            t = utils.container_of(t['thread_group']['next'],
> > -                                   task_ptr_type, "thread_group")
> > -            if t == g:
> > -                break
> > +        thread_head = t['signal']['thread_head']
> > +        for thread in lists.list_for_each_entry(thread_head,
> task_ptr_type, 'thread_node'):
> > +            yield thread
> >  
> >          t = g = utils.container_of(g['tasks']['next'],
> >                                     task_ptr_type, "tasks")
> 
> Thanks!
> 
> I do not know python, but it seems that with this patch we can kill g
> or t?
> Can't
> 
> def task_lists():
>     task_ptr_type = task_type.get_type().pointer()
>     init_task = gdb.parse_and_eval("init_task").address
>     t = init_task
> 
>     while True:
> thread_head = t['signal']['thread_head']
> for thread in lists.list_for_each_entry(thread_head, task_ptr_type,
> 'thread_node'):
>     yield thread
> 
> t = utils.container_of(t['tasks']['next'],
>        task_ptr_type, "tasks")
> if t == init_task:
>     return
> 
> work?

Yes, you are right.
I will fix it in v2.

Thanks,
Kuan-Ying Lee
> 
> Oleg.
>