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[v3,net,3/3] bpf: report RCU QS in cpumap kthread

Message ID 3112a13efb21893b6cf285b3757877dc466c5f58.1710346410.git.yan@cloudflare.com (mailing list archive)
State Superseded
Headers show
Series Report RCU QS for busy network kthreads | expand

Commit Message

Yan Zhai March 13, 2024, 4:25 p.m. UTC 
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: 6710e1126934 ("bpf: introduce new bpf cpu map type BPF_MAP_TYPE_CPUMAP")
Reviewed-by: Jesper Dangaard Brouer <hawk@kernel.org>
Signed-off-by: Yan Zhai <yan@cloudflare.com>
---
 kernel/bpf/cpumap.c | 3 +++
 1 file changed, 3 insertions(+)
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Patch

diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index ef82ffc90cbe..8f1d390bcbde 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -262,6 +262,7 @@  static int cpu_map_bpf_prog_run(struct bpf_cpu_map_entry *rcpu, void **frames,
 static int cpu_map_kthread_run(void *data)
 {
 	struct bpf_cpu_map_entry *rcpu = data;
+	unsigned long last_qs = jiffies;
 
 	complete(&rcpu->kthread_running);
 	set_current_state(TASK_INTERRUPTIBLE);
@@ -287,10 +288,12 @@  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();
 		}