diff options
Diffstat (limited to 'Documentation/core-api')
| -rw-r--r-- | Documentation/core-api/xarray.rst | 28 |
1 files changed, 19 insertions, 9 deletions
diff --git a/Documentation/core-api/xarray.rst b/Documentation/core-api/xarray.rst index 8a6e2087de77..616ac406bf86 100644 --- a/Documentation/core-api/xarray.rst +++ b/Documentation/core-api/xarray.rst @@ -119,18 +119,27 @@ Finally, you can remove all entries from an XArray by calling to free the entries first. You can do this by iterating over all present entries in the XArray using the :c:func:`xa_for_each` iterator. -ID assignment -------------- +Allocating XArrays +------------------ + +If you use :c:func:`DEFINE_XARRAY_ALLOC` to define the XArray, or +initialise it by passing ``XA_FLAGS_ALLOC`` to :c:func:`xa_init_flags`, +the XArray changes to track whether entries are in use or not. You can call :c:func:`xa_alloc` to store the entry at any unused index in the XArray. If you need to modify the array from interrupt context, you can use :c:func:`xa_alloc_bh` or :c:func:`xa_alloc_irq` to disable -interrupts while allocating the ID. Unlike :c:func:`xa_store`, allocating -a ``NULL`` pointer does not delete an entry. Instead it reserves an -entry like :c:func:`xa_reserve` and you can release it using either -:c:func:`xa_erase` or :c:func:`xa_release`. To use ID assignment, the -XArray must be defined with :c:func:`DEFINE_XARRAY_ALLOC`, or initialised -by passing ``XA_FLAGS_ALLOC`` to :c:func:`xa_init_flags`, +interrupts while allocating the ID. + +Using :c:func:`xa_store`, :c:func:`xa_cmpxchg` or :c:func:`xa_insert` +will mark the entry as being allocated. Unlike a normal XArray, storing +``NULL`` will mark the entry as being in use, like :c:func:`xa_reserve`. +To free an entry, use :c:func:`xa_erase` (or :c:func:`xa_release` if +you only want to free the entry if it's ``NULL``). + +You cannot use ``XA_MARK_0`` with an allocating XArray as this mark +is used to track whether an entry is free or not. The other marks are +available for your use. Memory allocation ----------------- @@ -338,7 +347,8 @@ to :c:func:`xas_retry`, and retry the operation if it returns ``true``. - :c:func:`xa_is_zero` - Zero entries appear as ``NULL`` through the Normal API, but occupy an entry in the XArray which can be used to reserve the index for - future use. + future use. This is used by allocating XArrays for allocated entries + which are ``NULL``. Other internal entries may be added in the future. As far as possible, they will be handled by :c:func:`xas_retry`. |