This function should be preferred, where feasible, over all the others.
These mappings are thread-local and CPU-local, meaning that the mapping
- can only be accessed from within this thread and the thread is bound the
- CPU while the mapping is active. Even if the thread is preempted (since
- preemption is never disabled by the function) the CPU can not be
- unplugged from the system via CPU-hotplug until the mapping is disposed.
+ can only be accessed from within this thread and the thread is bound to the
+ CPU while the mapping is active. Although preemption is never disabled by
+ this function, the CPU can not be unplugged from the system via
+ CPU-hotplug until the mapping is disposed.
It's valid to take pagefaults in a local kmap region, unless the context
in which the local mapping is acquired does not allow it for other reasons.
+ As said, pagefaults and preemption are never disabled. There is no need to
+ disable preemption because, when context switches to a different task, the
+ maps of the outgoing task are saved and those of the incoming one are
+ restored.
+
kmap_local_page() always returns a valid virtual address and it is assumed
that kunmap_local() will never fail.