Messages in this thread | | | Date | Tue, 28 May 2019 13:50:30 -0700 | From | "Paul E. McKenney" <> | Subject | Review of RCU-related patches in -rt |
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Hello, Sebastian,
Finally getting around to taking another look:
c7e07056a108 EXP rcu: skip the workqueue path on RT
This one makes sense given the later commit setting the rcu_normal_after_boot kernel parameter. Otherwise, it is slowing down expedited grace periods for no reason. But should the check also include rcu_normal_after_boot and rcu_normal? For example:
if ((IS_ENABLED(CONFIG_PREEMPT_RT_FULL) && (rcu_normal || rcu_normal_after_boot) || !READ_ONCE(rcu_par_gp_wq) || rcu_scheduler_active != RCU_SCHEDULER_RUNNING || rcu_is_last_leaf_node(rnp)) {
Alternatively, one approach would be to take the kernel parameters out in -rt:
static int rcu_normal_after_boot = IS_ENABLED(CONFIG_PREEMPT_RT_FULL); #ifndef CONFIG_PREEMPT_RT_FULL module_param(rcu_normal_after_boot, int, 0); #endif
And similar for rcu_normal and rcu_expedited.
Or is there some reason to allow run-time expedited grace periods in CONFIG_PREEMPT_RT_FULL=y kernels?
d1f52391bd8a rcu: Disable RCU_FAST_NO_HZ on RT
Looks good. More complexity could be added if too many people get themselves in trouble via "select RCU_FAST_NO_HZ".
42b346870326 rcu: make RCU_BOOST default on RT
To avoid complaints about this showing up when people don't expected, could you please instead "select RCU_BOOST" in the Kconfig definition of PREEMPT_RT_FULL?
Or do people really want to be able to disable boosting?
457c1b0d9c0e sched: Do not account rcu_preempt_depth on RT in might_sleep()
The idea behind this one is to avoid false-positive complaints about -rt's sleeping spinlocks, correct?
7ee13e640b01 rbtree: don't include the rcu header c9b0c9b87081 rtmutex: annotate sleeping lock context
No specific comments.
7912d002ebf9 rcu: Eliminate softirq processing from rcutree
This hasn't caused any problems in -rcu from what I can see. I am therefore planning to submit the -rcu variant of this to mainline during the next merge window.
f06d34ebdbbb srcu: Remove srcu_queue_delayed_work_on()
Looks plausible. I will check more carefully for mainline.
aeb04e894cc9 srcu: replace local_irqsave() with a locallock e48989b033ad irqwork: push most work into softirq context
These look to still be -rt only.
Thanx, Paul
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