[PATCH net] pktgen: use cpus_read_lock() in pg_net_init()

[PATCH net] pktgen: use cpus_read_lock() in pg_net_init()

[Eric Dumazet]

I have seen the WARN_ON(smp_processor_id() != cpu) firing
in pktgen_thread_worker() during tests.

We must use cpus_read_lock()/cpus_read_unlock()
around the for_each_online_cpu(cpu) loop.

While we are at it use WARN_ON_ONCE() to avoid a possible syslog flood.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/core/pktgen.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index ea55a758a475ab0ee22d9ac91f0ac9f0a6975e1f..197a50ef8e2e1bbe9f3906dfb80e80d913534b81 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -3654,7 +3654,7 @@ static int pktgen_thread_worker(void *arg)
 	struct pktgen_dev *pkt_dev = NULL;
 	int cpu = t->cpu;
 
-	WARN_ON(smp_processor_id() != cpu);
+	WARN_ON_ONCE(smp_processor_id() != cpu);
 
 	init_waitqueue_head(&t->queue);
 	complete(&t->start_done);
@@ -3989,6 +3989,7 @@ static int __net_init pg_net_init(struct net *net)
 		goto remove;
 	}
 
+	cpus_read_lock();
 	for_each_online_cpu(cpu) {
 		int err;
 
@@ -3997,6 +3998,7 @@ static int __net_init pg_net_init(struct net *net)
 			pr_warn("Cannot create thread for cpu %d (%d)\n",
 				   cpu, err);
 	}
+	cpus_read_unlock();
 
 	if (list_empty(&pn->pktgen_threads)) {
 		pr_err("Initialization failed for all threads\n");
-- 
2.46.0.184.g6999bdac58-goog

Re: [PATCH net] pktgen: use cpus_read_lock() in pg_net_init()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 21 Aug 2024 17:53:39 +0000 you wrote:
> I have seen the WARN_ON(smp_processor_id() != cpu) firing
> in pktgen_thread_worker() during tests.
> 
> We must use cpus_read_lock()/cpus_read_unlock()
> around the for_each_online_cpu(cpu) loop.
> 
> While we are at it use WARN_ON_ONCE() to avoid a possible syslog flood.
> 
> [...]

Here is the summary with links:
  - [net] pktgen: use cpus_read_lock() in pg_net_init()
    https://git.kernel.org/netdev/net/c/979b581e4c69

You are awesome, thank you!
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