bpf: report RCU QS in cpumap kthread

[ Upstream commit 00bf631 ] When there are heavy load, cpumap kernel threads can be busy polling packets from redirect queues and block out RCU tasks from reaching quiescent states. It is insufficient to just call cond_resched() in such context. Periodically raise a consolidated RCU QS before cond_resched fixes the problem. Fixes: 6710e11 ("bpf: introduce new bpf cpu map type BPF_MAP_TYPE_CPUMAP") Reviewed-by: Jesper Dangaard Brouer <[email protected]> Signed-off-by: Yan Zhai <[email protected]> Acked-by: Paul E. McKenney <[email protected]> Acked-by: Jesper Dangaard Brouer <[email protected]> Link: https://lore.kernel.org/r/c17b9f1517e19d813da3ede5ed33ee18496bb5d8.1710877680.git.yan@cloudflare.com Signed-off-by: Jakub Kicinski <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
frank-w · Mar 26, 2024 · 5942645 · 5942645
1 parent 3ffe591
commit 5942645
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
@@ -249,6 +249,7 @@ static void put_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
 static int cpu_map_kthread_run(void *data)
 {
 	struct bpf_cpu_map_entry *rcpu = data;
+	unsigned long last_qs = jiffies;
 
 	set_current_state(TASK_INTERRUPTIBLE);
 
@@ -271,10 +272,12 @@ static int cpu_map_kthread_run(void *data)
 			if (__ptr_ring_empty(rcpu->queue)) {
 				schedule();
 				sched = 1;
+				last_qs = jiffies;
 			} else {
 				__set_current_state(TASK_RUNNING);
 			}
 		} else {
+			rcu_softirq_qs_periodic(last_qs);
 			sched = cond_resched();
 		}