Re: local_irq_save not masking interrupts

[Esben Nielsen <nielsen.esben@gogglemail.com>]

On Tue, 26 Sep 2006, Alex Zeffertt wrote:

> Hi list,
>
> I'm having a strange problem with interrupts.  My platform is the
> MPC832xEMDS and the BSP I'm using (from Freescale) uses Linux-2.6.11.
>
> In the code below I enter a critical section with local_irq_save(),
> call request_irq() (from mpc832xemds_phy_interrupt_enable) 4 times,
> then exit the critical section using local_irq_restore.
>
>     /* Enable interrupts from PHYs */
>     local_irq_save(flags);
>     for (i = 0; i < driver_data->num_phys; i++) {
>         struct atm_dev *dev = driver_data->dev_data[i]->dev;
>         printk("%s/%d\n",__FUNCTION__,__LINE__);
>         RETURN_ON_ERROR(mpc832xemds_phy_interrupt_enable(dev));
>     }
>     local_irq_restore(flags);
>

This is a pure side-comment:

Please, don't use local_irq_save() for a critical region. Use
spin_lock_irqsave(), for 3 reasons:
1) SMP.
2) Preempt-realtime is like SMP not happy about using local_irq_save().
3) Read-ability: It is more clear what data is protected when there is a 
named lock object in the code.

You might not care about 1) and 2) but 3) should matter for you. And 
remember: When CONFIG_SMP is not set spin_lock_irqsave() will just 
become a local_irq_save().

Esben