From c5bacd94173ec49d7dce7ac7c64bbdde3a6e69ae Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 20 Jul 2018 14:18:23 -0700 Subject: rcu: Motivate Tiny RCU forward progress If a long-running CPU-bound in-kernel task invokes call_rcu(), the callback won't be invoked until the next context switch. If there are no other runnable tasks (which is not an uncommon situation on deep embedded systems), the callback might never be invoked. This commit therefore causes rcu_check_callbacks() to ask the scheduler for a context switch if there are callbacks posted that are still waiting for a grace period. Suggested-by: Peter Zijlstra Signed-off-by: Paul E. McKenney --- kernel/rcu/tiny.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'kernel/rcu/tiny.c') diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c index a77853b73bfe..1745d30e170e 100644 --- a/kernel/rcu/tiny.c +++ b/kernel/rcu/tiny.c @@ -78,8 +78,12 @@ void rcu_qs(void) */ void rcu_check_callbacks(int user) { - if (user) + if (user) { rcu_qs(); + } else if (rcu_ctrlblk.donetail != rcu_ctrlblk.curtail) { + set_tsk_need_resched(current); + set_preempt_need_resched(); + } } /* Invoke the RCU callbacks whose grace period has elapsed. */ -- cgit