[PATCH 6.6.y] i40e: Fix preempt count leak in napi poll tracepoint

[PATCH 6.6.y] i40e: Fix preempt count leak in napi poll tracepoint

[charles_xu]

From: Thomas Gleixner <tglx@kernel.org>

[ Upstream commit 4b3d54a85bd37ebf2d9836f0d0de775c0ff21af9 ]

Using get_cpu() in the tracepoint assignment causes an obvious preempt
count leak because nothing invokes put_cpu() to undo it:

  softirq: huh, entered softirq 3 NET_RX with preempt_count 00000100, exited with 00000101?

This clearly has seen a lot of testing in the last 3+ years...

Use smp_processor_id() instead.

Fixes: 6d4d584a7ea8 ("i40e: Add i40e_napi_poll tracepoint")
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Cc: Tony Nguyen <anthony.l.nguyen@intel.com>
Cc: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Cc: intel-wired-lan@lists.osuosl.org
Cc: netdev@vger.kernel.org
Reviewed-by: Joe Damato <joe@dama.to>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Charles Xu <charles_xu@189.cn>
---
 drivers/net/ethernet/intel/i40e/i40e_trace.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_trace.h b/drivers/net/ethernet/intel/i40e/i40e_trace.h
index 33b4e30f5e00..9b735a9e2114 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_trace.h
+++ b/drivers/net/ethernet/intel/i40e/i40e_trace.h
@@ -88,7 +88,7 @@ TRACE_EVENT(i40e_napi_poll,
 		__entry->rx_clean_complete = rx_clean_complete;
 		__entry->tx_clean_complete = tx_clean_complete;
 		__entry->irq_num = q->irq_num;
-		__entry->curr_cpu = get_cpu();
+		__entry->curr_cpu = smp_processor_id();
 		__assign_str(qname, q->name);
 		__assign_str(dev_name, napi->dev ? napi->dev->name : NO_DEV);
 		__assign_bitmask(irq_affinity, cpumask_bits(&q->affinity_mask),
-- 
2.35.3

Re: [PATCH 6.6.y] i40e: Fix preempt count leak in napi poll tracepoint

[Jacob Keller]

On 4/21/2026 12:18 AM, charles_xu@189.cn wrote:
> From: Thomas Gleixner <tglx@kernel.org>
> 
> [ Upstream commit 4b3d54a85bd37ebf2d9836f0d0de775c0ff21af9 ]
> 
> Using get_cpu() in the tracepoint assignment causes an obvious preempt
> count leak because nothing invokes put_cpu() to undo it:
> 
>   softirq: huh, entered softirq 3 NET_RX with preempt_count 00000100, exited with 00000101?
> 
> This clearly has seen a lot of testing in the last 3+ years...
> 
> Use smp_processor_id() instead.
> 
> Fixes: 6d4d584a7ea8 ("i40e: Add i40e_napi_poll tracepoint")
> Signed-off-by: Thomas Gleixner <tglx@kernel.org>
> Cc: Tony Nguyen <anthony.l.nguyen@intel.com>
> Cc: Przemek Kitszel <przemyslaw.kitszel@intel.com>
> Cc: intel-wired-lan@lists.osuosl.org
> Cc: netdev@vger.kernel.org
> Reviewed-by: Joe Damato <joe@dama.to>
> Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
> Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
> Signed-off-by: Charles Xu <charles_xu@189.cn>
> ---

This was already backported 6.12, but wasn't in v6.6. The v6.6 tree does
have the i40e_napi_poll tracepoint, so it makes sense to backport this
there as well.

Acked-by: Jacob Keller <jacob.e.keller@intel.com>