[RFC DEPT v16] Question for dept.

[Yeo Reum Yun <YeoReum.Yun@arm.com>]

Hi Byungchul,

Thanks for your great work for the latest dept patch.

But I have a some quetions with the below dept log supplied from 
Yunseong Kim<yskelg@gmail.com>

...
[13304.604203] context A
[13304.604209]    [S] lock(&uprobe->register_rwsem:0)
[13304.604217]    [W] __wait_rcu_gp(<sched>:0)
[13304.604226]    [E] unlock(&uprobe->register_rwsem:0)
[13304.604234]
[13304.604239] context B 
[13304.604244]    [S] lock(event_mutex:0)
[13304.604252]    [W] lock(&uprobe->register_rwsem:0)
[13304.604261]    [E] unlock(event_mutex:0)
[13304.604269]
[13304.604274] context C
[13304.604279]    [S] lock(&ctx->mutex:0)
[13304.604287]    [W] lock(event_mutex:0)
[13304.604295]    [E] unlock(&ctx->mutex:0)
[13304.604303]
[13304.604308] context D
[13304.604313]    [S] lock(&sig->exec_update_lock:0)
[13304.604322]    [W] lock(&ctx->mutex:0)
[13304.604330]    [E] unlock(&sig->exec_update_lock:0)
[13304.604338]
[13304.604343] context E
[13304.604348]    [S] lock(&f->f_pos_lock:0)
[13304.604356]    [W] lock(&sig->exec_update_lock:0)
[13304.604365]    [E] unlock(&f->f_pos_lock:0)
[13304.604373]
[13304.604378] context F
[13304.604383]    [S] (unknown)(<sched>:0)
[13304.604391]    [W] lock(&f->f_pos_lock:0)
[13304.604399]    [E] try_to_wake_up(<sched>:0)
[13304.604408]
[13304.604413] context G
[13304.604418]    [S] lock(btrfs_trans_num_writers:0)
[13304.604427]    [W] btrfs_commit_transaction(<sched>:0)
[13304.604436]    [E] unlock(btrfs_trans_num_writers:0)
[13304.604445]
[13304.604449] context H
[13304.604455]    [S] (unknown)(<sched>:0)
[13304.604463]    [W] lock(btrfs_trans_num_writers:0)
[13304.604471]    [E] try_to_wake_up(<sched>:0)
[13304.604484] context I
[13304.604490]    [S] (unknown)(<sched>:0)
[13304.604498]    [W] synchronize_rcu_expedited_wait_once(<sched>:0)
[13304.604507]    --------------- >8 timeout ---------------
[13304.604527] context J
[13304.604533]    [S] (unknown)(<sched>:0)
[13304.604541]    [W] synchronize_rcu_expedited(<sched>:0)
[13304.604549]    [E] try_to_wake_up(<sched>:0)

[end of circular]
...

1. I wonder how context A could be printed with 
    [13304.604217]    [W] __wait_rcu_gp(<sched>:0) 
    since, the completion's dept map will be initailized with 
       sdt_might_sleep_start_timeout((x)->dmap, -1L);
   
    I think last dept_task's stage_sched_map affects this wrong print.
    Should this be fixed with:

 @@ -2713,6 +2713,7 @@ void dept_stage_wait(struct dept_map *m, struct dept_key *k,
        if (m) {
                dt->stage_m = *m;
                dt->stage_real_m = m;
+               dt->stage_sched_map = false;

                /*
                 * Ensure dt->stage_m.keys != NULL and it works with the
    
2. Whenever prints the dependency which initalized with sdt_might_sleep_start_timeout() currently it prints
   (unknown)(<sched>:0) only.
   Would it much better to print task information? (pid, comm and other).    

Thanks.