On Tue, 07 Jun 2016 21:56:38 +0200 Peter Zijlstra <[email protected]> wrote:
> From: Xunlei Pang <[email protected]> > > Currently dl tasks will actually return at the very beginning > of rt_mutex_adjust_prio_chain() in !detect_deadlock cases: > > if (waiter->prio == task->prio) { > if (!detect_deadlock) > goto out_unlock_pi; // out here > else > requeue = false; > } > > As the deadline value of blocked deadline tasks(waiters) without > changing their sched_class(thus prio doesn't change) never changes, > this seems reasonable, but it actually misses the chance of updating > rt_mutex_waiter's "dl_runtime(period)_copy" if a waiter updates its > deadline parameters(dl_runtime, dl_period) or boosted waiter changes > to !deadline class. > > Thus, force deadline task not out by adding the !dl_prio() condition. > > [peterz: I should introduce more task state comparators like > rt_mutex_waiter_less, all PI prio comparisons already have this DL > exception, except this one] > > Cc: Steven Rostedt <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Cc: Juri Lelli <[email protected]> > Signed-off-by: Xunlei Pang <[email protected]> > Signed-off-by: Peter Zijlstra (Intel) <[email protected]> > Link: > http://lkml.kernel.org/r/[email protected] > --- > kernel/locking/rtmutex.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- a/kernel/locking/rtmutex.c > +++ b/kernel/locking/rtmutex.c > @@ -488,7 +488,7 @@ static int rt_mutex_adjust_prio_chain(st > * enabled we continue, but stop the requeueing in the chain > * walk. > */ > - if (waiter->prio == task->prio) { > + if (waiter->prio == task->prio && !dl_task(task)) { Isn't task the owner of the lock? What happens if the waiter is a deadline task? -- Steve > if (!detect_deadlock) > goto out_unlock_pi; > else >
