[PATCH net] net: airoha: Fix schedule while atomic in airoha_ppe_deinit()

[PATCH net] net: airoha: Fix schedule while atomic in airoha_ppe_deinit()

[Lorenzo Bianconi]

Rely on rcu_replace_pointer in airoha_ppe_deinit routine in order to fix
schedule while atomic issue.

Fixes: 00a7678310fe3 ("net: airoha: Introduce flowtable offload support")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 drivers/net/ethernet/airoha/airoha_ppe.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/airoha/airoha_ppe.c b/drivers/net/ethernet/airoha/airoha_ppe.c
index 0caabb0c3aa06948e46ad087c50eba5babc81994..2221bafaf7c9fed73dcf8d30ff3b1c5eecc463d4 100644
--- a/drivers/net/ethernet/airoha/airoha_ppe.c
+++ b/drivers/net/ethernet/airoha/airoha_ppe.c
@@ -1547,13 +1547,16 @@ void airoha_ppe_deinit(struct airoha_eth *eth)
 {
 	struct airoha_npu *npu;
 
-	rcu_read_lock();
-	npu = rcu_dereference(eth->npu);
+	mutex_lock(&flow_offload_mutex);
+
+	npu = rcu_replace_pointer(eth->npu, NULL,
+				  lockdep_is_held(&flow_offload_mutex));
 	if (npu) {
 		npu->ops.ppe_deinit(npu);
 		airoha_npu_put(npu);
 	}
-	rcu_read_unlock();
+
+	mutex_unlock(&flow_offload_mutex);
 
 	rhashtable_destroy(&eth->ppe->l2_flows);
 	rhashtable_destroy(&eth->flow_table);

---
base-commit: 7b8e9264f55a9c320f398e337d215e68cca50131
change-id: 20251223-airoha-fw-ethtool-21f54b02c98b

Best regards,
-- 
Lorenzo Bianconi <lorenzo@kernel.org>

Re: [PATCH net] net: airoha: Fix schedule while atomic in airoha_ppe_deinit()

[Jakub Kicinski]

On Tue, 23 Dec 2025 22:56:44 +0100 Lorenzo Bianconi wrote:
> Rely on rcu_replace_pointer in airoha_ppe_deinit routine in order to fix
> schedule while atomic issue.

The information in the commit message is not sufficient.
What "schedule while atomic issue"?

> -	npu = rcu_dereference(eth->npu);
> +	mutex_lock(&flow_offload_mutex);
> +
> +	npu = rcu_replace_pointer(eth->npu, NULL,
> +				  lockdep_is_held(&flow_offload_mutex));
>  	if (npu) {
>  		npu->ops.ppe_deinit(npu);
>  		airoha_npu_put(npu);
-- 
pw-bot: cr

Re: [PATCH net] net: airoha: Fix schedule while atomic in airoha_ppe_deinit()

[Lorenzo Bianconi]

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> On Tue, 23 Dec 2025 22:56:44 +0100 Lorenzo Bianconi wrote:
> > Rely on rcu_replace_pointer in airoha_ppe_deinit routine in order to fix
> > schedule while atomic issue.
> 
> The information in the commit message is not sufficient.
> What "schedule while atomic issue"?

The issue is we run kzalloc() with GFP_KERNEL in airoha_npu_ppe_deinit()
in atomic context but we do not really need atomic context there.
I will fix the commit log in v2.

Regards,
Lorenzo

> 
> > -	npu = rcu_dereference(eth->npu);
> > +	mutex_lock(&flow_offload_mutex);
> > +
> > +	npu = rcu_replace_pointer(eth->npu, NULL,
> > +				  lockdep_is_held(&flow_offload_mutex));
> >  	if (npu) {
> >  		npu->ops.ppe_deinit(npu);
> >  		airoha_npu_put(npu);
> -- 
> pw-bot: cr

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