Re: [RFC] logdev debugging memory device for tough to debug areas

[Ingo Molnar <mingo@elte.hu>]

* Steven Rostedt <rostedt@goodmis.org> wrote:

> Also, I'm almost done adding the pending owner work against .41-11. I 
> see you now have 41-13, and if you already implemented it, let me 
> know. [...]

nope, i havent touched that area of code, knowing that you are working 
on it.

> [...] I've been fighting your deadlock detection to make sure it works 
> with the changes. Then finally I found a race condition that I'm 
> solving.

great - just send it along when you have it.

> To have a task take back the ownership, I had the stealer call 
> task_blocks_on_lock on the task that it stole it from. To get this to 
> work, when a task is given the pending ownership, it doesn't NULL the 
> blocked_on at that point (although the waiter->task is set to NULL).  
> But this gives the race condition in pi_setprio where it checks for 
> p->blocked_on still exists. Reason is that I don't want the waking up 
> of a process to call any more locks. To solve this, I had to (and this 
> is what I don't like right now) add another flag for the process 
> called PF_BLOCKED. So that this can tell the pi_setprio when to stop.  
> This flag is set in task_blocks_on_lock and cleared in pick_new_owner 
> where the setting of blocked_on to NULL use to be.

which locks are affected? I'd prefer the simplest solution. If there's 
more overhead with deadlock detection (which is a debugging feature), 
that doesnt matter much.

> Unless you already implemented this, I'll have a patch for you to look 
> at later today, and you can then (if you want) critique it :-)

sure.

	Ingo