On Wed, Sep 16, 2020 at 11:32:00AM -0700, Linus Torvalds wrote:
On Wed, Sep 16, 2020 at 8:29 AM Paul E. McKenney paulmck@kernel.org wrote:
All fair, but some of us need to write code that must handle being invoked from a wide variety of contexts.
Note that I think that core functionality is different from random drivers.
Of course core code can (and will) look at things like
if (in_interrupt()) .. schedule work asynchronously ..because core code ends up being called from odd places, and code like that is expected to have understanding of the rules it plays with.
But something like RCU is a very different beast from some "walk the scatter-gather list" code.
RCU does its work in the background, and works with lots of different things. And it's so core and used everywhere that it knows about these things. I mean, we literally have special code explicitly to let RCU know "we entered kernel context now".
But something like a driver list walking thing should not be doing different things behind peoples back depending on whether they hold spinlocks or not. It should either just work regardless, or there should be a flag (or special interface) for the "you're being called in a crtitical region".
Because dynamically changing behavior really is very confusing.
Whew! I feel much better now. ;-)
Thanx, Paul