On 12/06/13 17:07, Steven Rostedt wrote:
On Wed, 2013-06-12 at 14:15 +0200, Peter Zijlstra wrote:
So I absolutely hate this API because people can (and invariably will)
abuse it; much like they did/do preempt_enable_no_resched().
Me too.
IIRC Thomas even maps preempt_enable_no_resched() to preempt_enable() in
-rt to make sure we don't miss preemption points due to stupidity.
He converted the 'few' sane sites to use schedule_preempt_disabled(). In
that vein, does it make sense to introduce schedule_spin_locked()?
I was thinking the exact same thing when I read this patch. This is a
strict policy that we should enforce and not let individual developers
implement. Yes, a schedule_spin_unlock() would work nicely. The API will
enforce the two to be used together. Otherwise, I can envision seeing
things like:
preempt_disable();
[...]
spin_lock(x);
spin_unlock_no_resched(x);
[...]
preempt_enable();
And developers having no idea why the above is broken. Although, I would
say the above is broken for other reasons, but I was just using that to
show the craziness such an API would give to us.
-- Steve
In additional to my previous letter. If spin_lock is locked then irqs
must be disabled. So sorry for the noise.
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