[PATCH v3] serial: stm32: Merge hard IRQ and threaded IRQ handling into single IRQ handler

[Marek Vasut]

On 1/6/23 11:56, Johan Hovold wrote:
> On Thu, Jan 05, 2023 at 09:46:57PM +0100, Marek Vasut wrote:
>> On 12/27/22 15:56, Johan Hovold wrote:
>>
>> [...]
>>
>>>> @@ -793,27 +794,13 @@ static irqreturn_t stm32_usart_interrupt(int irq, void *ptr)
>>>>    	}
>>>>    
>>>>    	if ((sr & USART_SR_TXE) && !(stm32_port->tx_ch)) {
>>>> -		spin_lock(&port->lock);
>>>> +		spin_lock_irqsave(&port->lock, flags);
>>>>    		stm32_usart_transmit_chars(port);
>>>> -		spin_unlock(&port->lock);
>>>> +		spin_unlock_irqrestore(&port->lock, flags);
>>>
>>> This is not needed as the handler runs with interrupts disabled.
>>
>> On SMP system, another thread on another core can call
>> stm32_usart_transmit_chars() . I don't think removing the locking is
>> correct ?
> 
> I didn't say that you should remove the locking, which is very much
> needed. There's just no need to disable interrupts in a (non-threaded)
> interrupt handler as that has already been done by IRQ core (and, yes,
> that is also the case with forced threading).

Ah, understood.