Avoiding sleep while holding a spinlock

Question

I've recently read section 5.5.2 (Spinlocks and Atomic Context) of LDDv3 book:

Avoiding sleep while holding a lock can be more difficult; many kernel functions can sleep, and this behavior is not always well documented. Copying data to or from user space is an obvious example: the required user-space page may need to be swapped in from the disk before the copy can proceed, and that operation clearly requires a sleep. Just about any operation that must allocate memory can sleep; kmalloc can decide to give up the processor, and wait for more memory to become available unless it is explicitly told not to. Sleeps can happen in surprising places; writing code that will execute under a spinlock requires paying attention to every function that you call.

It's clear to me that spinlocks must always be held for the minimum time possible and I think that it's relatively easy to write correct spinlock-using code from scratch.

Suppose, however, that we have a big project where spinlocks are widely used. How can we make sure that functions called from critical sections protected by spinlocks will never sleep?

Thanks in advance!

Answer 1

What about enabling "Sleep-inside-spinlock checking" for your kernel ? It is usually found under Kernel Debugging when you run make config. You might also try to duplicate its behavior in your code.