Re: [dpdk-dev] [EXT] Re: [PATCH v2 1/4] eal: add API to check if its interrupt context

[Harman Kalra <hkalra@marvell.com>]

On Thu, Nov 28, 2019 at 08:45:42AM -0800, Stephen Hemminger wrote:
> On Thu, 28 Nov 2019 08:10:23 +0000
> Harman Kalra <hkalra@marvell.com> wrote:
> 
> > On Wed, Nov 27, 2019 at 04:03:19PM -0800, Stephen Hemminger wrote:
> > > External Email
> > > 
> > > ----------------------------------------------------------------------
> > > On Wed, 27 Nov 2019 15:52:19 +0530
> > > Sunil Kumar Kori <skori@marvell.com> wrote:
> > >   
> > > >  
> > > > +/**
> > > > + * @warning
> > > > + * @b EXPERIMENTAL: this API may change without prior notice
> > > > + *
> > > > + * Check if currently executing in interrupt context
> > > > + *
> > > > + * @return
> > > > + *  - positive in case of interrupt context
> > > > + *  - zero in case of process context
> > > > + *  - negative if unsuccessful
> > > > + */
> > > > +__rte_experimental
> > > > +int
> > > > +rte_thread_is_intr(void);  
> > > 
> > > If you only need this in drivers, it should be internal not exposed
> > > as part of API  
> > 
> > Sorry, but can you please help me understand the query. Do you mean:
> > * Since "rte_thread_is_intr"  would be used only used by
> > libraries/drivers and not by any external application, rather having
> > it in "rte_interrupt.h", we should have it in some internal header
> > file like "eal_private.h" ??
> > 
> > ANS - Yes we can do that but since all other related APIs like
> > "rte_intr_ack", "rte_intr_enable/disable" which are also used by
> > drivers/lib and not application, are prototyped in "rte_interupt.h".
> > 
> > OR do u mean
> > * Since only octeontx2 driver is using this, why it is exposed as an API
> > rather it should be defined as some driver internal function ??
> > 
> > ANS - "rte_thread_is_intr" is an counter part of "in_interrupt()" in
> > DPDK, which will return whether the current execution is in interrupt
> > context. This helps in dealing with nested interrupts case. We faced a
> > similar case while handling hotplug probing initiated via secondary
> > process.
> > We believe this API could be very useful for many drivers which might
> > end up in handling nested interrupts case.
> > 
> > Thanks
> > Harman
> 
> What I meant was that some functions in EAL are documented as
> being internal (flagged with @internal) and don't show up in
> the documented API.
> 
> My concern is that if we make this part of the public API, it makes
> it harder to change structural things like the interrupt thread
> later.  The interrupt thread is already problematic for several
> other usages.
> 

I think now I understood your point, I will move prototype of this API to
"common/include/rte_eal_interrupts.h", flag it as @internal
and resend next version. I think this file was created for such
APIs only as its description says.

/**
 * @file rte_eal_interrupts.h
 * @internal
 *
 * Contains function prototypes exposed by the EAL for interrupt handling by
 * drivers and other DPDK internal consumers.
 */

Thanks
Harman