Re: [PATCH net-next] net: mana: Add CQE polling as first-level TX timeout recovery

[Sahil Chandna <sahilchandna@linux.microsoft.com>]

On 12-11-2026 17:37, Breno Leitao wrote:
> Hello Sahil,
> 
> On Thu, Nov 12, 2026 at 04:57:18AM -0600, Sahil Chandna wrote:
>> Implement a graduated recovery approach: on the first TX timeout (or
>> when the previous timeout was more than 2 minutes ago), schedule NAPI on
>> the stalled queue's TX CQ via napi_schedule(). This triggers
>> mana_poll_tx_cq() through the normal NAPI path, processing any pending
>> completions without relying on the interrupt and recovering
>> missed-interrupt scenarios without queue reset.
> 
> Which interrupt is being missed here?
> 
Hi Breno,

It is the TX CQ completion interrupt. After NAPI finishes, it re-arms
the TX CQ. When a new CQE arrives, the hardware post EQE, which raises
the MSI-X and schedules NAPI. If that notification for the TX CQ is lost
, NAPI never runs for the TX CQ and pending_sends never drains and the
queue stays stopped,  so napi_schedule() polls the CQ, reaps the CQEs
and re-arms it.
>> If any subsequent TX timeout fires on any queue, within 2 minutes of
>> the previous one, escalate to the existing port-level detach/attach
>> reset, as the CQE poll did not recover the queue.
> 
> How was 2 minutes chosen? mana sets watchdog_timeo to 15 * HZ, no?
The watchdog_timeo is TX stall timeout setting i.e if a queue remains
stalled for this much time, it trigger watchdog timeout. Here, 2 minute
is not timeout/wait. The 2 minutes here is for deciding whether a new
queue stall event is a repeat of the previous incident or a new,
unrelated one that should get the cheap poll first. For e.g. if a queue
gets stalled, 15 * HZ sec later, timeout occurs and this patch trigger
manual NAPI, if another stall occurs (it can be on any queue) within 2
minutes of last one, the existing recovery mechanism of mana
detach/attach will be tried.The patch is adding a first level less
destructive recovery first.
For selecting 2 minutes, I do not have any hardware basis for it afaik,
but I can confirm and check with our host team as well.
Hope this helps !
Regards,
Sahil