Yes, Yanmin's manual revert got rid of the new semaphores entirely. Which
was what, 7500 lines of code removed that got reverted.
And the *WHOLE* and *ONLY* excuse for dropping the spinlock lock_kernel
was this (and I quote your message):
remove the !PREEMPT_BKL code.
this removes 160 lines of legacy code.
in other words, your only stated valid reason for getting rid of the
spinlock was 160 lines, and the comment didn't even match what it did (it
removed the spinlocks entirely, not just the preemptible version).
In contrast, the revert adds 7500 lines. If you go by the only documented
reason for the crap that is the current BKL, then I know which one I'll
take. I'll take the spinlock back, and I'd rather put preemption back
than ever take those semaphores.
And even that's ignoring another issue: did anybody ever even do that AIM7
benchmark comparing spinlocks to the semaphore-BKL? It's quite possible
that the semaphores (even the well-behaved ones) behaved worse than the
spinlocks.
Linus
--
