Re: [PATCH] cleanup sched_yield (sys)call nesting.

Sven-Thorsten Dietrich
2009-11-18T21:04:50Z

On Wed, 2009-11-18 at 21:56 +0100, Thomas Gleixner wrote:
> On Wed, 18 Nov 2009, Sven-Thorsten Dietrich wrote:
> > On Wed, 2009-11-18 at 17:52 +0100, Jean Delvare wrote:
> > > On Wed, 18 Nov 2009 17:28:53 +0100, Leon Woestenberg wrote:
> > > > On Wed, Nov 18, 2009 at 2:05 AM, Alan Cox <alan-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org> wrote:
> > > > > Our timers are very efficient and some day we will need to make jiffies a
> > > > > function and stop the timer ticking for best performance. At that point
> > > > > timers are probably the most efficient way to do much of this.
> > > >
> > > > The problem with I2C bitbanged is the stringent timing, we need a way
> > > > to have fine-grained sleeping
> > > > mixed with real-time tasks in order to make this work.
> > >
> > > FWIW, the problem that was initially reported has nothing to do with
> > > this. i2c-algo-bit used mdelay() during transactions, not yield().
> > > yield() is used only in once place, _between_ transactions attempts.
> > > There are no strict timing constraints there.
> > >
> >
> > I agree that dropping out sched_yield entirely should maybe start by
> > deprecating / flagging as a warning in sched_rt.c.
>
> Errm, that's unrelated to sched_rt.c.
>
> yield() in the kernel in general is needs to be deprecated.
>
> > This is just a minimal cleanup I stumbled across while looking at it -
> > to get away from the uglyness of calling into the syscall interface from
> > inside the Kernel.
>
> And why exactly is that ugly ?

Calling from a function returning void into a non-void function and then
ignoring the return code ?