The GFP flags – digging deeper

With regard to our discussions on the low-level page allocator APIs, the first parameter to every function is the so-called GFP mask. When discussing the APIs and their usage, we mentioned a key rule.

If in process context and it is safe to sleep, use the GFP_KERNEL flag. If it is unsafe to sleep (typically, when in any type of interrupt context or when holding some types of locks), you must use the GFP_ATOMIC flag.

We elaborate on this in the following sections.