Arnd Bergmann noted that he's working on removing the BKL from the Linux kernel, "I've spent some time continuing the work of the people on Cc and many others to remove the big kernel lock from Linux and I now have [a] bkl-removal branch in my git tree". He went on to explain that his branch is working, and lets him run the Linux kernel, "on [a] quad-core machine with the only users of the BKL being mostly obscure device driver modules." Arnd noted that this effort has a long history, "the oldest patch in this series is roughly eight years old and is Willy's patch to remove the BKL from fs/locks.c, and I took a series of patches from Jan that removes it from most of the VFS."
Arnd noted that his patch adds a global mutex to the TTY layer, which he called the 'Big TTY Mutex' and described as, "the basic idea here is to make recursive locking and the release-on-sleep explicit, so every mutex_lock, wait_event, workqueue_flush and schedule in the TTY layer now explicitly releases the BTM before blocking."Alan Cox suggested that this portion of the patch was best dropped for now, "it would be nice to get the other bits in first removing BKL from most of the kernel and building kernels which are non BKL except for the tty layer. That (after Ingo's box from hell has run it a bit) would reasonably test the assertion that the tty layer has no BKL requirements that are driven by [code] external to tty layer code."Andrew Morton suggested that the patches be pushed upstream to their appropriate maintainers for an additional sanity check, "Seems that there might be a few tricksy bits in here. Please do push at least the non-obvious parts out to the relevant people."