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/this_cpu_ops.rst | 22 |
3 files changed, 20 insertions, 10 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/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 ----------------------------- |