diff options
Diffstat (limited to 'Documentation/core-api')
| -rw-r--r-- | Documentation/core-api/min_heap.rst | 4 | ||||
| -rw-r--r-- | Documentation/core-api/printk-formats.rst | 4 | ||||
| -rw-r--r-- | Documentation/core-api/refcount-vs-atomic.rst | 37 | ||||
| -rw-r--r-- | Documentation/core-api/this_cpu_ops.rst | 22 | ||||
| -rw-r--r-- | Documentation/core-api/xarray.rst | 14 |
5 files changed, 64 insertions, 17 deletions
diff --git a/Documentation/core-api/min_heap.rst b/Documentation/core-api/min_heap.rst index 683bc6d09f00..9f57766581df 100644 --- a/Documentation/core-api/min_heap.rst +++ b/Documentation/core-api/min_heap.rst @@ -47,8 +47,8 @@ Example: #define MIN_HEAP_PREALLOCATED(_type, _name, _nr) struct _name { - int nr; /* Number of elements in the heap */ - int size; /* Maximum number of elements that can be held */ + size_t nr; /* Number of elements in the heap */ + size_t size; /* Maximum number of elements that can be held */ _type *data; /* Pointer to the heap data */ _type preallocated[_nr]; /* Static preallocated array */ } diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index ecccc0473da9..4bdc394e86af 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -661,7 +661,7 @@ Do *not* use it from C. Thanks ====== -If you add other %p extensions, please extend <lib/test_printf.c> with -one or more test cases, if at all feasible. +If you add other %p extensions, please extend <lib/tests/printf_kunit.c> +with one or more test cases, if at all feasible. Thank you for your cooperation and attention. diff --git a/Documentation/core-api/refcount-vs-atomic.rst b/Documentation/core-api/refcount-vs-atomic.rst index 79a009ce11df..94e628c1eb49 100644 --- a/Documentation/core-api/refcount-vs-atomic.rst +++ b/Documentation/core-api/refcount-vs-atomic.rst @@ -86,7 +86,19 @@ Memory ordering guarantee changes: * none (both fully unordered) -case 2) - increment-based ops that return no value +case 2) - non-"Read/Modify/Write" (RMW) ops with release ordering +----------------------------------------------------------------- + +Function changes: + + * atomic_set_release() --> refcount_set_release() + +Memory ordering guarantee changes: + + * none (both provide RELEASE ordering) + + +case 3) - increment-based ops that return no value -------------------------------------------------- Function changes: @@ -98,7 +110,7 @@ Memory ordering guarantee changes: * none (both fully unordered) -case 3) - decrement-based RMW ops that return no value +case 4) - decrement-based RMW ops that return no value ------------------------------------------------------ Function changes: @@ -110,7 +122,7 @@ Memory ordering guarantee changes: * fully unordered --> RELEASE ordering -case 4) - increment-based RMW ops that return a value +case 5) - increment-based RMW ops that return a value ----------------------------------------------------- Function changes: @@ -126,7 +138,20 @@ Memory ordering guarantees changes: result of obtaining pointer to the object! -case 5) - generic dec/sub decrement-based RMW ops that return a value +case 6) - increment-based RMW ops with acquire ordering that return a value +--------------------------------------------------------------------------- + +Function changes: + + * atomic_inc_not_zero() --> refcount_inc_not_zero_acquire() + * no atomic counterpart --> refcount_add_not_zero_acquire() + +Memory ordering guarantees changes: + + * fully ordered --> ACQUIRE ordering on success + + +case 7) - generic dec/sub decrement-based RMW ops that return a value --------------------------------------------------------------------- Function changes: @@ -139,7 +164,7 @@ Memory ordering guarantees changes: * fully ordered --> RELEASE ordering + ACQUIRE ordering on success -case 6) other decrement-based RMW ops that return a value +case 8) other decrement-based RMW ops that return a value --------------------------------------------------------- Function changes: @@ -154,7 +179,7 @@ Memory ordering guarantees changes: .. note:: atomic_add_unless() only provides full order on success. -case 7) - lock-based RMW +case 9) - lock-based RMW ------------------------ Function changes: diff --git a/Documentation/core-api/this_cpu_ops.rst b/Documentation/core-api/this_cpu_ops.rst index 91acbcf30e9b..533ac5dd5750 100644 --- a/Documentation/core-api/this_cpu_ops.rst +++ b/Documentation/core-api/this_cpu_ops.rst @@ -138,12 +138,22 @@ get_cpu/put_cpu sequence requires. No processor number is available. Instead, the offset of the local per cpu area is simply added to the per cpu offset. -Note that this operation is usually used in a code segment when -preemption has been disabled. The pointer is then used to -access local per cpu data in a critical section. When preemption -is re-enabled this pointer is usually no longer useful since it may -no longer point to per cpu data of the current processor. - +Note that this operation can only be used in code segments where +smp_processor_id() may be used, for example, where preemption has been +disabled. The pointer is then used to access local per cpu data in a +critical section. When preemption is re-enabled this pointer is usually +no longer useful since it may no longer point to per cpu data of the +current processor. + +The special cases where it makes sense to obtain a per-CPU pointer in +preemptible code are addressed by raw_cpu_ptr(), but such use cases need +to handle cases where two different CPUs are accessing the same per cpu +variable, which might well be that of a third CPU. These use cases are +typically performance optimizations. For example, SRCU implements a pair +of counters as a pair of per-CPU variables, and rcu_read_lock_nmisafe() +uses raw_cpu_ptr() to get a pointer to some CPU's counter, and uses +atomic_inc_long() to handle migration between the raw_cpu_ptr() and +the atomic_inc_long(). Per cpu variables and offsets ----------------------------- diff --git a/Documentation/core-api/xarray.rst b/Documentation/core-api/xarray.rst index f6a3eef4fe7f..c6c91cbd0c3c 100644 --- a/Documentation/core-api/xarray.rst +++ b/Documentation/core-api/xarray.rst @@ -489,7 +489,19 @@ Storing ``NULL`` into any index of a multi-index entry will set the entry at every index to ``NULL`` and dissolve the tie. A multi-index entry can be split into entries occupying smaller ranges by calling xas_split_alloc() without the xa_lock held, followed by taking the lock -and calling xas_split(). +and calling xas_split() or calling xas_try_split() with xa_lock. The +difference between xas_split_alloc()+xas_split() and xas_try_alloc() is +that xas_split_alloc() + xas_split() split the entry from the original +order to the new order in one shot uniformly, whereas xas_try_split() +iteratively splits the entry containing the index non-uniformly. +For example, to split an order-9 entry, which takes 2^(9-6)=8 slots, +assuming ``XA_CHUNK_SHIFT`` is 6, xas_split_alloc() + xas_split() need +8 xa_node. xas_try_split() splits the order-9 entry into +2 order-8 entries, then split one order-8 entry, based on the given index, +to 2 order-7 entries, ..., and split one order-1 entry to 2 order-0 entries. +When splitting the order-6 entry and a new xa_node is needed, xas_try_split() +will try to allocate one if possible. As a result, xas_try_split() would only +need 1 xa_node instead of 8. Functions and structures ======================== |