Re: [PATCH] net: stmmac: Improve Tx timer arm logic further

[Nazle Asmade, Muhammad Nazim Amirul]

On 25/5/2026 9:46 pm, Andrew Lunn wrote:
> On Sun, May 24, 2026 at 11:16:53PM -0700, muhammad.nazim.amirul.nazle.asmade@xxxxxxxxxx wrote:
>> From: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@xxxxxxxxxx>
>>
>> Currently hrtimer_start is called even if hrtimer is
>> active. This is unnecessary and expensive in some targets.
>> This patch avoids calling hrtimer_start unnecessarily.
>>
>> Signed-off-by: Rohan G Thomas <rohan.g.thomas@xxxxxxxxx>
>> Signed-off-by: Nazim Amirul <muhammad.nazim.amirul.nazle.asmade@xxxxxxxxxx>
>> ---
>>   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 12 +++++++-----
>>   1 file changed, 7 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> index 3591755ea30b..35da51c26248 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>> @@ -3341,12 +3341,14 @@ static void stmmac_tx_timer_arm(struct stmmac_priv *priv, u32 queue)
>>   	 * Try to cancel any timer if napi is scheduled, timer will be armed
>>   	 * again in the next scheduled napi.
>>   	 */
>> -	if (unlikely(!napi_is_scheduled(napi)))
>> -		hrtimer_start(&tx_q->txtimer,
>> -			      STMMAC_COAL_TIMER(tx_coal_timer),
>> -			      HRTIMER_MODE_REL);
>> -	else
>> +	if (unlikely(!napi_is_scheduled(napi))) {
>> +		if (unlikely(!(hrtimer_active(&tx_q->txtimer))))
>> +			hrtimer_start(&tx_q->txtimer,
>> +				      STMMAC_COAL_TIMER(tx_coal_timer),
>> +				      HRTIMER_MODE_REL);
> 
> Is there a race condition here? I've not thought about it enough to
> know if there is/is not.
> 
> Also, does this change the meaning of tx_coal_timer?
> 
> I think the commit message needs expanding, to cover these issues. For
> performance changes, it is also normal to include some performance
> numbers, before/after, in the commit message.
> 
>      Andrew
> 
> ---
> pw-bot: cr
Hi Maxime, Andrew

Thanks for the quick review! I already send out v2 which applied all the 
comments.
https://lore.kernel.org/all/20260526051921.14540-1-muhammad.nazim.amirul.nazle.asmade@xxxxxxxxxx/