4 files changed, 191 insertions, 7 deletions
diff --git a/Documentation/core-api/genalloc.rst b/Documentation/core-api/genalloc.rst
new file mode 100644
index 000000000000..6b38a39fab24
--- /dev/null
+++ b/Documentation/core-api/genalloc.rst
@@ -0,0 +1,144 @@
+The genalloc/genpool subsystem
+==============================
+
+There are a number of memory-allocation subsystems in the kernel, each
+aimed at a specific need.  Sometimes, however, a kernel developer needs to
+implement a new allocator for a specific range of special-purpose memory;
+often that memory is located on a device somewhere.  The author of the
+driver for that device can certainly write a little allocator to get the
+job done, but that is the way to fill the kernel with dozens of poorly
+tested allocators.  Back in 2005, Jes Sorensen lifted one of those
+allocators from the sym53c8xx_2 driver and posted_ it as a generic module
+for the creation of ad hoc memory allocators.  This code was merged
+for the 2.6.13 release; it has been modified considerably since then.
+
+.. _posted: https://lwn.net/Articles/125842/
+
+Code using this allocator should include <linux/genalloc.h>.  The action
+begins with the creation of a pool using one of:
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_create		
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: devm_gen_pool_create
+
+A call to :c:func:`gen_pool_create` will create a pool.  The granularity of
+allocations is set with min_alloc_order; it is a log-base-2 number like
+those used by the page allocator, but it refers to bytes rather than pages.
+So, if min_alloc_order is passed as 3, then all allocations will be a
+multiple of eight bytes.  Increasing min_alloc_order decreases the memory
+required to track the memory in the pool.  The nid parameter specifies
+which NUMA node should be used for the allocation of the housekeeping
+structures; it can be -1 if the caller doesn't care.
+
+The "managed" interface :c:func:`devm_gen_pool_create` ties the pool to a
+specific device.  Among other things, it will automatically clean up the
+pool when the given device is destroyed.
+
+A pool is shut down with:
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_destroy
+
+It's worth noting that, if there are still allocations outstanding from the
+given pool, this function will take the rather extreme step of invoking
+BUG(), crashing the entire system.  You have been warned.
+
+A freshly created pool has no memory to allocate.  It is fairly useless in
+that state, so one of the first orders of business is usually to add memory
+to the pool.  That can be done with one of:
+
+.. kernel-doc:: include/linux/genalloc.h
+   :functions: gen_pool_add
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_add_virt
+
+A call to :c:func:`gen_pool_add` will place the size bytes of memory
+starting at addr (in the kernel's virtual address space) into the given
+pool, once again using nid as the node ID for ancillary memory allocations.
+The :c:func:`gen_pool_add_virt` variant associates an explicit physical
+address with the memory; this is only necessary if the pool will be used
+for DMA allocations.
+
+The functions for allocating memory from the pool (and putting it back)
+are:
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_alloc
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_dma_alloc
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_free
+
+As one would expect, :c:func:`gen_pool_alloc` will allocate size< bytes
+from the given pool.  The :c:func:`gen_pool_dma_alloc` variant allocates
+memory for use with DMA operations, returning the associated physical
+address in the space pointed to by dma.  This will only work if the memory
+was added with :c:func:`gen_pool_add_virt`.  Note that this function
+departs from the usual genpool pattern of using unsigned long values to
+represent kernel addresses; it returns a void * instead.
+
+That all seems relatively simple; indeed, some developers clearly found it
+to be too simple.  After all, the interface above provides no control over
+how the allocation functions choose which specific piece of memory to
+return.  If that sort of control is needed, the following functions will be
+of interest:
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_alloc_algo
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_set_algo
+
+Allocations with :c:func:`gen_pool_alloc_algo` specify an algorithm to be
+used to choose the memory to be allocated; the default algorithm can be set
+with :c:func:`gen_pool_set_algo`.  The data value is passed to the
+algorithm; most ignore it, but it is occasionally needed.  One can,
+naturally, write a special-purpose algorithm, but there is a fair set
+already available:
+
+- gen_pool_first_fit is a simple first-fit allocator; this is the default
+  algorithm if none other has been specified.
+
+- gen_pool_first_fit_align forces the allocation to have a specific
+  alignment (passed via data in a genpool_data_align structure).
+
+- gen_pool_first_fit_order_align aligns the allocation to the order of the
+  size.  A 60-byte allocation will thus be 64-byte aligned, for example.
+
+- gen_pool_best_fit, as one would expect, is a simple best-fit allocator.
+
+- gen_pool_fixed_alloc allocates at a specific offset (passed in a
+  genpool_data_fixed structure via the data parameter) within the pool.
+  If the indicated memory is not available the allocation fails.
+
+There is a handful of other functions, mostly for purposes like querying
+the space available in the pool or iterating through chunks of memory.
+Most users, however, should not need much beyond what has been described
+above.  With luck, wider awareness of this module will help to prevent the
+writing of special-purpose memory allocators in the future.
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_virt_to_phys
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_for_each_chunk
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: addr_in_gen_pool
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_avail
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_size
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: gen_pool_get
+
+.. kernel-doc:: lib/genalloc.c
+   :functions: of_gen_pool_get
diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst
index 0606be3a3111..d5bbe035316d 100644
--- a/Documentation/core-api/index.rst
+++ b/Documentation/core-api/index.rst
@@ -20,6 +20,7 @@ Core utilities
    genericirq
    flexible-arrays
    librs
+   genalloc
 
 Interfaces for kernel debugging
 ===============================
diff --git a/Documentation/core-api/kernel-api.rst b/Documentation/core-api/kernel-api.rst
index 17b00914c6ab..5da10184d908 100644
--- a/Documentation/core-api/kernel-api.rst
+++ b/Documentation/core-api/kernel-api.rst
@@ -344,3 +344,38 @@ codecs, and devices with strict requirements for interface clocking.
 
 .. kernel-doc:: include/linux/clk.h
    :internal:
+
+Synchronization Primitives
+==========================
+
+Read-Copy Update (RCU)
+----------------------
+
+.. kernel-doc:: include/linux/rcupdate.h
+
+.. kernel-doc:: include/linux/rcupdate_wait.h
+
+.. kernel-doc:: include/linux/rcutree.h
+
+.. kernel-doc:: kernel/rcu/tree.c
+
+.. kernel-doc:: kernel/rcu/tree_plugin.h
+
+.. kernel-doc:: kernel/rcu/tree_exp.h
+
+.. kernel-doc:: kernel/rcu/update.c
+
+.. kernel-doc:: include/linux/srcu.h
+
+.. kernel-doc:: kernel/rcu/srcutree.c
+
+.. kernel-doc:: include/linux/rculist_bl.h
+
+.. kernel-doc:: include/linux/rculist.h
+
+.. kernel-doc:: include/linux/rculist_nulls.h
+
+.. kernel-doc:: include/linux/rcu_sync.h
+
+.. kernel-doc:: kernel/rcu/sync.c
+
diff --git a/Documentation/core-api/workqueue.rst b/Documentation/core-api/workqueue.rst
index ffdec94fbca1..00a5ba51e63f 100644
--- a/Documentation/core-api/workqueue.rst
+++ b/Documentation/core-api/workqueue.rst
@@ -39,8 +39,8 @@ up.
 Although MT wq wasted a lot of resource, the level of concurrency
 provided was unsatisfactory.  The limitation was common to both ST and
 MT wq albeit less severe on MT.  Each wq maintained its own separate
-worker pool.  A MT wq could provide only one execution context per CPU
-while a ST wq one for the whole system.  Work items had to compete for
+worker pool.  An MT wq could provide only one execution context per CPU
+while an ST wq one for the whole system.  Work items had to compete for
 those very limited execution contexts leading to various problems
 including proneness to deadlocks around the single execution context.
 
@@ -151,7 +151,7 @@ Application Programming Interface (API)
 
 ``alloc_workqueue()`` allocates a wq.  The original
 ``create_*workqueue()`` functions are deprecated and scheduled for
-removal.  ``alloc_workqueue()`` takes three arguments - @``name``,
+removal.  ``alloc_workqueue()`` takes three arguments - ``@name``,
 ``@flags`` and ``@max_active``.  ``@name`` is the name of the wq and
 also used as the name of the rescuer thread if there is one.
 
@@ -197,7 +197,7 @@ resources, scheduled and executed.
   served by worker threads with elevated nice level.
 
   Note that normal and highpri worker-pools don't interact with
-  each other.  Each maintain its separate pool of workers and
+  each other.  Each maintains its separate pool of workers and
   implements concurrency management among its workers.
 
 ``WQ_CPU_INTENSIVE``
@@ -243,11 +243,15 @@ throttling the number of active work items, specifying '0' is
 recommended.
 
 Some users depend on the strict execution ordering of ST wq.  The
-combination of ``@max_active`` of 1 and ``WQ_UNBOUND`` is used to
-achieve this behavior.  Work items on such wq are always queued to the
-unbound worker-pools and only one work item can be active at any given
+combination of ``@max_active`` of 1 and ``WQ_UNBOUND`` used to
+achieve this behavior.  Work items on such wq were always queued to the
+unbound worker-pools and only one work item could be active at any given
 time thus achieving the same ordering property as ST wq.
 
+In the current implementation the above configuration only guarantees
+ST behavior within a given NUMA node. Instead ``alloc_ordered_queue()`` should
+be used to achieve system-wide ST behavior.
+
 
 Example Execution Scenarios
 ===========================