[PATCH v0] scripts/gdb: Use a generator instead of iterator for task list

[PATCH v0] scripts/gdb: Use a generator instead of iterator for task list

[Daniel Wagner]

I am trying to debug something here and gave your patches a spin.
I found a small issue when trying to access threads instead only
processes. 

See you next week in Duesseldorf!

Daniel Wagner (1):
  scripts/gdb: Use a generator instead of iterator for task list

 scripts/gdb/linux/tasks.py | 50 +++++++++++++++++++---------------------------
 1 file changed, 20 insertions(+), 30 deletions(-)

-- 
1.9.3

[PATCH v0] scripts/gdb: Use a generator instead of iterator for task list

[Daniel Wagner]

The iterator does not return any task_struct from the thread_group list
because the first condition in the 'if not t or ...' will only be the
first time None.

Instead of keeping track of the state ourself in the next() function,
we fall back using Python's generator.

Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/tasks.py | 50 +++++++++++++++++++---------------------------
 1 file changed, 20 insertions(+), 30 deletions(-)

diff --git a/scripts/gdb/linux/tasks.py b/scripts/gdb/linux/tasks.py
index 0008e75..e2037d9 100644
--- a/scripts/gdb/linux/tasks.py
+++ b/scripts/gdb/linux/tasks.py
@@ -18,38 +18,28 @@ from linux import utils
 
 task_type = utils.CachedType("struct task_struct")
 
-
-class TaskList:
-    def __init__(self):
-        global task_type
-        self.task_ptr_type = task_type.get_type().pointer()
-        self.init_task = gdb.parse_and_eval("init_task")
-        self.curr_group = self.init_task.address
-        self.curr_task = None
-
-    def __iter__(self):
-        return self
-
-    def __next__(self):
-        t = self.curr_task
-        if not t or t == self.curr_group:
-            self.curr_group = \
-                utils.container_of(self.curr_group['tasks']['next'],
-                                   self.task_ptr_type, "tasks")
-            if self.curr_group == self.init_task.address:
-                raise StopIteration
-            t = self.curr_task = self.curr_group
-        else:
-            self.curr_task = \
-                utils.container_of(t['thread_group']['next'],
-                                   self.task_ptr_type, "thread_group")
-        return t
-
-    def next(self):
-        return self.__next__()
+def task_lists():
+    global task_type
+    task_ptr_type = task_type.get_type().pointer()
+    init_task = gdb.parse_and_eval("init_task").address
+    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
+
+        t = g = utils.container_of(g['tasks']['next'],
+                                   task_ptr_type, "tasks")
+        if t == init_task:
+            return
 
 def get_task_by_pid(pid):
-    for task in TaskList():
+    for task in task_lists():
         if int(task['pid']) == pid:
             return task
     return None
-- 
1.9.3

Re: [PATCH v0] scripts/gdb: Use a generator instead of iterator for task list

[Jan Kiszka]

On 2014-10-09 10:03, Daniel Wagner wrote:
> The iterator does not return any task_struct from the thread_group list
> because the first condition in the 'if not t or ...' will only be the
> first time None.
> 
> Instead of keeping track of the state ourself in the next() function,
> we fall back using Python's generator.
> 
> Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
> Cc: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>  scripts/gdb/linux/tasks.py | 50 +++++++++++++++++++---------------------------
>  1 file changed, 20 insertions(+), 30 deletions(-)
> 
> diff --git a/scripts/gdb/linux/tasks.py b/scripts/gdb/linux/tasks.py
> index 0008e75..e2037d9 100644
> --- a/scripts/gdb/linux/tasks.py
> +++ b/scripts/gdb/linux/tasks.py
> @@ -18,38 +18,28 @@ from linux import utils
>  
>  task_type = utils.CachedType("struct task_struct")
>  
> -
> -class TaskList:
> -    def __init__(self):
> -        global task_type
> -        self.task_ptr_type = task_type.get_type().pointer()
> -        self.init_task = gdb.parse_and_eval("init_task")
> -        self.curr_group = self.init_task.address
> -        self.curr_task = None
> -
> -    def __iter__(self):
> -        return self
> -
> -    def __next__(self):
> -        t = self.curr_task
> -        if not t or t == self.curr_group:
> -            self.curr_group = \
> -                utils.container_of(self.curr_group['tasks']['next'],
> -                                   self.task_ptr_type, "tasks")
> -            if self.curr_group == self.init_task.address:
> -                raise StopIteration
> -            t = self.curr_task = self.curr_group
> -        else:
> -            self.curr_task = \
> -                utils.container_of(t['thread_group']['next'],
> -                                   self.task_ptr_type, "thread_group")
> -        return t
> -
> -    def next(self):
> -        return self.__next__()
> +def task_lists():
> +    global task_type
> +    task_ptr_type = task_type.get_type().pointer()
> +    init_task = gdb.parse_and_eval("init_task").address
> +    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
> +
> +        t = g = utils.container_of(g['tasks']['next'],
> +                                   task_ptr_type, "tasks")
> +        if t == init_task:
> +            return
>  
>  def get_task_by_pid(pid):
> -    for task in TaskList():
> +    for task in task_lists():
>          if int(task['pid']) == pid:
>              return task
>      return None
> 

Thanks for the fix (and the nice simplification), added to my queue.
I'll repost the whole series ASAP.

Jan

-- 
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