This is a note to let you know that I've just added the patch titled
bpf: report RCU QS in cpumap kthread
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bpf-report-rcu-qs-in-cpumap-kthread.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0eb9577c00e31696eb9d52e77c629849da0a3cfc
Author: Yan Zhai <yan@xxxxxxxxxxxxxx>
Date: Tue Mar 19 13:44:40 2024 -0700
bpf: report RCU QS in cpumap kthread
[ Upstream commit 00bf63122459e87193ee7f1bc6161c83a525569f ]
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@xxxxxxxxxx>
Signed-off-by: Yan Zhai <yan@xxxxxxxxxxxxxx>
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Acked-by: Jesper Dangaard Brouer <hawk@xxxxxxxxxx>
Link: https://lore.kernel.org/r/c17b9f1517e19d813da3ede5ed33ee18496bb5d8.1710877680.git.yan@xxxxxxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index f7de5b313cc5b..a8429cfb4ae8c 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -305,6 +305,7 @@ 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);
@@ -330,10 +331,12 @@ 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();
}
