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SubjectRe: test6-lowlatency-D1 results: 50msec + hangs ....
On Sat, Aug 05, 2000 at 05:52:26PM -0700, David S. Miller wrote:
> Date: Sun, 6 Aug 2000 01:43:04 +0100
> From: Philipp Rumpf <prumpf@parcelfarce.linux.theplanet.co.uk>
>
> That's bogus on UP (spin_is_locked always returns 0).
>
> I think it would be reasonably nice to have something like
>
> spin_lock_held(spinlock_t *lock);
>
> that returns 1 for UP and spin_is_locked(lock) for SMP - basically
>
> Really, whatever you name it, the question of a lock being held or not
> on UP has zero meaning. There is no correct return value, period.

Uhm, I disagree. "Am I holding this lock" is always true on UP. "Is
someone else holding this lock" is always false. "Am I holding this lock"
also isn't the same as spin_is_locked on SMP since you want to look at
who's holding it when debugging is enabled. Same goes for "Is someone
else holding this lock".

> No matter what constant answer you decide to give on UP it will always
> be incorrect. I know, because there were old bits of assertions in

You're right. But no-one actually cares about whether a lock is held -
they care about whether they're holding it or someone else is holding it
or no-one's holding it.

Philipp

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