Re: [patch 2/2] rtmutex: Detect changes in the pi lock chain

From: Steven Rostedt
Date: Fri Jun 06 2014 - 05:58:35 EST


On Fri, 6 Jun 2014 11:48:59 +0200
Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

>
>
> hehe, I can almost follow this code :-)
>
> How about something like this on top?

Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>

-- Steve

>
> ---
> --- a/kernel/locking/rtmutex.c
> +++ b/kernel/locking/rtmutex.c
> @@ -260,6 +260,11 @@ static void rt_mutex_adjust_prio(struct
> */
> int max_lock_depth = 1024;
>
> +static inline struct rt_mutex *task_blocked_on(struct task_struct *p)
> +{
> + return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL;
> +}
> +
> /*
> * Adjust the priority chain. Also used for deadlock detection.
> * Decreases task's usage by one - may thus free the task.
> @@ -443,10 +448,7 @@ static int rt_mutex_adjust_prio_chain(st
> * blocked itself. If yes we store a pointer to the lock for
> * the lock chain change detection above.
> */
> - if (task->pi_blocked_on)
> - next_lock = task->pi_blocked_on->lock;
> - else
> - next_lock = NULL;
> + next_lock = task_blocked_on(task);
>
> raw_spin_unlock_irqrestore(&task->pi_lock, flags);
>
> @@ -569,7 +571,7 @@ static int task_blocks_on_rt_mutex(struc
> {
> struct task_struct *owner = rt_mutex_owner(lock);
> struct rt_mutex_waiter *top_waiter = waiter;
> - struct rt_mutex *next_lock = NULL;
> + struct rt_mutex *next_lock;
> unsigned long flags;
> int chain_walk, res;
>
> @@ -614,8 +616,8 @@ static int task_blocks_on_rt_mutex(struc
> } else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) {
> chain_walk = 1;
> }
> - if (owner->pi_blocked_on)
> - next_lock = owner->pi_blocked_on->lock;
> +
> + next_lock = task_blocked_on(owner);
>
> raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
> if (!chain_walk)
> @@ -705,8 +707,7 @@ static void remove_waiter(struct rt_mute
> }
> __rt_mutex_adjust_prio(owner);
>
> - if (owner->pi_blocked_on)
> - next_lock = owner->pi_blocked_on->lock;
> + next_lock = task_blocked_on(owner);
>
> raw_spin_unlock_irqrestore(&owner->pi_lock, flags);
> }

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