Re: [PATCH 1/2] hung_task: Show the blocker task if the task is hung on mutex

[Sergey Senozhatsky]

On (25/02/20 08:09), Masami Hiramatsu wrote:
> So something like this?
> 
> unsigned int	block_flags;
> union {
> 	struct mutex	*mutex;
> 	struct rwsem	+rwsem;
> 	struct rtmutex	*rtmutex;
> } blocked_on;
> 
> enum {
> 	BLOCKED_ON_MUTEX;
> 	BLOCKED_ON_RWSEM;
> 	BLOCKED_ON_RTMUTEX;
> 	BLOCKED_ON_IO;
> } block_reason;

I totally like this and always wanted to have something simlar,
something for all "sleepable" synchronization primitives, lightweight
enough (memory and CPU usage wise) to run on consumer devices.  I was
thinking of a rhashtable where each entry represents "sleepable"
primitive with a "owner" pointer and a list of "blocked on" tasks.
But I'm sure you'll have a better idea.

If I may add a couple of "wishes", can we also add:
- completions (so that things like wait_for_completion and
  synchronize srcu get covered)
- wait on bit (so that things like lock_buffer and so on get covered)