KernelTrap: Making The BKL Preemptable

“Continuing his effort to minimize latency in the 2.6 kernel,
Ingo Molnar offered a patch to ‘get rid of Linux’s Big Kernel Lock
as we know it today.’ He explains that he does this by replacing
the BKL spinlock and depth counter with a special recursive
semaphore. Ingo goes on to explain three main advantages of this
approach; code utilizing the BKL is now fully preemptable, no time
is wasted spinning on the BKL if there’s BKL contention, and it is
believed to be fully backwards compatible.

“Linus Torvalds was not impressed saying, ‘I really think this
is wrong.’ He went to explain that he wasn’t against the concept,
but had some issues with the implemenation, and would be quite
interested in seeing performance numbers…”

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