Commit-ID: c5bacd94173ec49d7dce7ac7c64bbdde3a6e69ae
Gitweb: https://git.kernel.org/tip/c5bacd94173ec49d7dce7ac7c64bbdde3a6e69ae
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Fri, 20 Jul 2018 14:18:23 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Thu, 30 Aug 2018 16:03:41 -0700
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 <peterz@xxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tiny.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
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. */
|