Re: [PATCH] Fix the "foreach DE" task identifier displays incorrect state tasks.

[lijiang <lijiang@xxxxxxxxxx>]

Thank you for the comments, Kazu.

On Mon, Jul 31, 2023 at 10:08 AM HAGIO KAZUHITO(萩尾　一仁) <k-hagio-ab@xxxxxxx> wrote:

On 2023/07/28 20:15, Lianbo Jiang wrote:
> Currently, the "foreach DE ps -m" command may display "DE" as well as
> "ZO" state tasks as below:
>
>    crash> foreach DE ps -m
>    ...
>    [0 00:00:00.040] [ZO]  PID: 11458    TASK: ffff91c75680d280  CPU: 7    COMMAND: "ora_w01o_p01mci"
>    [0 00:00:00.044] [ZO]  PID: 49118    TASK: ffff91c7bf3e8000  CPU: 19   COMMAND: "oracle_49118_p0"
>    [0 00:00:00.050] [ZO]  PID: 28748    TASK: ffff91a7cbde3180  CPU: 2    COMMAND: "ora_imr0_p01sci"
>    [0 00:00:00.050] [DE]  PID: 28405    TASK: ffff91a7c8eb0000  CPU: 27   COMMAND: "ora_vktm_p01sci"
>    [0 00:00:00.051] [ZO]  PID: 31716    TASK: ffff91a7f7192100  CPU: 6    COMMAND: "ora_p001_p01sci"
>    ...

Could you elaborate on why this happens?

When the "DE" identifier is specified in the foreach command, it needs to skip the non-"DE" tasks. Currently, crash doesn't deal with this case, only handles some cases, such as "_RUNNING_", "_UNINTERRUPTIBLE_", "_NOLOAD_", etc. So most tasks will be displayed directly.

I'm concerned about the difference of the conditions between printing
the "DE" state in task_state_string() and printing a "DE" task in the
foreach function in your patch:

char *
task_state_string(ulong task, char *buf, int verbose)
{
...
         if ((state & _DEAD_) && !set) {
                 sprintf(buf, "DE");
                 valid++;
                 set++;
         }

On the other hand, the following means that "state == _DEAD_" is the
"DE" state, not "state & _DEAD".  So I'm wondering if "foreach DE"
command might drop some "DE" tasks with your patch?

The condition "state & _DEAD" can not filter out the tasks with a state value of 0x50(0x10 + 0x40). It indicates that the "ZO" state tasks will be always displayed, when the "DE" identifier is specified.

I just did the debug on it, let me share an example:

crash> foreach DE ps -m

...

foreach: state: 0x60, task_state: 0x50
[0 00:00:00.040] [ZO]  PID: 11458    TASK: ffff91c75680d280  CPU: 7    COMMAND: "ora_w01o_p01mci"
foreach: state: 0x60, task_state: 0x50
[0 00:00:00.044] [ZO]  PID: 49118    TASK: ffff91c7bf3e8000  CPU: 19   COMMAND: "oracle_49118_p0"
foreach: state: 0x60, task_state: 0x50
[0 00:00:00.050] [ZO]  PID: 28748    TASK: ffff91a7cbde3180  CPU: 2    COMMAND: "ora_imr0_p01sci"
foreach: state: 0x60, task_state: 0x60
[0 00:00:00.050] [DE]  PID: 28405    TASK: ffff91a7c8eb0000  CPU: 27   COMMAND: "ora_vktm_p01sci"
foreach: state: 0x60, task_state: 0x50
[0 00:00:00.051] [ZO]  PID: 31716    TASK: ffff91a7f7192100  CPU: 6    COMMAND: "ora_p001_p01sci"

...

The DEAD state value is 0x60(0x20 + 0x40), the actual task state value is 0x50(0x10 + 0x40), and the ZOMBIE state value is 0x10, regardless of the "task_state(task) & _DEAD_" or "task_state(task) & _ZOMBIE_", the result is always true. So the condition "state & _DEAD" can not handle this case.

And also the actual task has a "DE" state value of 0x60.

...

foreach: state: 0x60, task_state: 0x60
[0 00:00:00.050] [DE]  PID: 28405    TASK: ffff91a7c8eb0000  CPU: 27   COMMAND: "ora_vktm_p01sci"

...

crash> help -t

...

           RUNNING:   0 (0x0)
     INTERRUPTIBLE:   1 (0x1)
   UNINTERRUPTIBLE:   2 (0x2)
           STOPPED:   4 (0x4)
   TRACING_STOPPED:   8 (0x8)
            ZOMBIE:  16 (0x10)
              DEAD:  32 and 64 (0x20 and 0x40)
          WAKEKILL: 128 (0x80)
            WAKING: 256 (0x100)
            PARKED: 512 (0x200)
crash> 

Thanks.

Lianbo

 > +                            if (task_state(tc->task) != _DEAD_)
 > +                                    continue;

Thanks,
Kazu

>
> That is not expected behavior, the "foreach" command needs to handle
> such cases. Let's add a check to determine if the task state identifier
> is specified and the task state identifier is equal to the "DE", so that
> it can filter out the non-"DE" state tasks.
>
> With the patch:
>    crash> foreach DE ps -m
>    [0 00:00:00.050] [DE]  PID: 28405    TASK: ffff91a7c8eb0000  CPU: 27   COMMAND: "ora_vktm_p01sci"
>    crash>
>
> Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx>
> ---
>   task.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/task.c b/task.c
> index b9076da35565..4f40c396b195 100644
> --- a/task.c
> +++ b/task.c
> @@ -7043,6 +7043,9 @@ foreach(struct foreach_data *fd)
>                       if (fd->state == _RUNNING_) {
>                               if (task_state(tc->task) != _RUNNING_)
>                                       continue;
> +                     } else if (fd->state == _DEAD_) {
> +                             if (task_state(tc->task) != _DEAD_)
> +                                     continue;
>                       } else if (fd->state & _UNINTERRUPTIBLE_) {
>                               if (!(task_state(tc->task) & _UNINTERRUPTIBLE_))
>                                       continue;

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