diff options
| -rw-r--r-- | Documentation/mm/highmem.rst | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/Documentation/mm/highmem.rst b/Documentation/mm/highmem.rst index e045a4b7b3da..0f731d9196b0 100644 --- a/Documentation/mm/highmem.rst +++ b/Documentation/mm/highmem.rst @@ -60,14 +60,19 @@ list shows them in order of preference of use. 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. |