[Click] [PATCH 2/2] Task: Kill process_pending dead lock

[Eddie Kohler]

Joonwoo,

Thanks very much for this patch and as usual for all your Click work!!

About this patch, though.  This patch does not make sense to me.  The 
Task::add_pending() function does NOT attempt to lock the RouterThread's 
_task_lock.  It locks the Master::_task_lock.  And none of the code that 
manipulates Master::_task_lock looks like it could cause deadlock 
(Master::_task_lock is held for short periods of time with no functions). 
Task::add_pending() does call RouterThread::add_pending(), but this function 
is safe to call without RouterThread::_task_lock.

So, can you explain in more detail what deadlock you thought you fixed with 
this patch?  Is my analysis wrong?  Does SpinlockIRQ need updating along the 
lines of Spinlock to pin a thread to the current CPU?

Eddie


Joonwoo Park wrote:
> Hello Eddie,
> 
> I think the function Task::add_pending() should haven't called while
> task is locked since it might cause dead lock.
> This patch fixes it by unlocking before calling add_pending.
> 
> Please consider applying this patch.
> 
> Thanks,
> Joonwoo