Re: [RFC PATCH 2/3] docs: scheduler: Add scheduler overview documentation

[Peter Zijlstra]

On Wed, Apr 01, 2020 at 01:47:04PM +0200, Daniel Bristot de Oliveira wrote:
> On 4/1/20 12:35 PM, Peter Zijlstra wrote:
> >> +Scheduler State Transition
> >> +==========================
> >> +
> >> +A very high level scheduler state transition flow with a few states can be
> >> +depicted as follows.
> >> +
> >> +.. kernel-render:: DOT
> >> +   :alt: DOT digraph of Scheduler state transition
> >> +   :caption: Scheduler state transition
> >> +
> >> +   digraph sched_transition {
> >> +      node [shape = point,  label="exisiting task\n calls fork()"]; fork
> >> +      node [shape = box, label="TASK_NEW\n(Ready to run)"] tsk_new;
> >> +      node [shape = box, label="TASK_RUNNING\n(Ready to run)"] tsk_ready_run;
> >> +      node [shape = box, label="TASK_RUNNING\n(Running)"] tsk_running;
> >> +      node [shape = box, label="TASK_DEAD\nEXIT_ZOMBIE"] exit_zombie;
> >> +      node [shape = box, label="TASK_INTERRUPTIBLE\nTASK_UNINTERRUPTIBLE\nTASK_WAKEKILL"] tsk_int;
> >> +      fork -> tsk_new [ label = "task\nforks" ];
> >> +      tsk_new -> tsk_ready_run;
> >> +      tsk_ready_run -> tsk_running [ label = "schedule() calls context_switch()" ];
> >> +      tsk_running -> tsk_ready_run [ label = "task is pre-empted" ];
> >> +      subgraph int {
> >> +         tsk_running -> tsk_int [ label = "task needs to wait for event" ];
> >> +         tsk_int ->  tsk_ready_run [ label = "event occurred" ];
> >> +      }
> >> +      tsk_int ->  exit_zombie [ label = "task exits via do_exit()" ];
> >> +   }
> > And that is a prime example of why I hates RST, it pretty much mandates
> > you view this with something other than a text editor.
> 
> The good thing about the dot format is that we can convert it to many other
> formats, including text:

Oh, I know and love dot files, I generate them occasionally. But they
stink as end-result, which is what it is here.

If you can't read a document (or worse comment) in a code editor it's
broken (and yes, I know some subsystems have a different opinion here).