[Intel-wired-lan] i40e: Fix preempt count leak in napi poll tracepoint
Thomas Gleixner
tglx at kernel.org
Mon Feb 9 22:56:29 UTC 2026
On Mon, Feb 09 2026 at 14:07, Joe Damato wrote:
> On Sat, Feb 07, 2026 at 11:50:23AM +0100, Thomas Gleixner wrote:
>> 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...
>
> I'm the author who introduced the bug. FWIW, I did use it quite a bit when I
> had i40e devices.
Right, but always with PREEMPT_NONE and no debug option which would
enforce PREEMPT_COUNT ...
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