Re: RT patch acceptance

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Tue, 24 May 2005, john cooper wrote:

> [...] 
> I'd like to hear some technical arguments of why IRQ threads
> are held with such suspicion.  Also it isn't the case prior
> mechanisms are being obsoleted.   Exception context interrupt
> processing and raw_spinlocks to synchronize with them are
> still available and will be for those edge cases which
> are not addressable via spinlock-mutexes.
>

Performance! Even on RT systems you do NOT make all interrupts run in
threads. Simple devices like UARTS run everything in interrupt context.
Introducing a context switch for every character received on such a
channel can be _very_ expensive.

I think it would be safe to convert almost every driver back to run in
exception context and use raw spinlocks for locking accordingly. Very few
driver actually does a lot of work on the interrupt level. Only those
devices high bandwidth and no DMA is a problem (old IDE and ethernet
devices spring to mind).

Therefore a framework where it can be configured per device would be the
ideal solution.

I do not know the structure of the code very well and I do not have any
time to look into it now. But I could imagine kbuild can be set up to
change the relavant between being a mutex and a raw spinlocks depending on
which code runs in exception context or in a thread.

> -john
> 
> 

Esben


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux