X-Git-Url: http://git.rot13.org/?a=blobdiff_plain;f=Documentation%2Flocal_ops.txt;h=4269a1105b378fafcc689435a2531b9d9d4287db;hb=6bb8383bebc02dae08a17f561401f58005f75c03;hp=1a45f11e645e978f445ba7396f0c5411a1695e06;hpb=61edab8d144ae7b4d7206b91adec947579a73c0a;p=powerpc.git diff --git a/Documentation/local_ops.txt b/Documentation/local_ops.txt index 1a45f11e64..4269a1105b 100644 --- a/Documentation/local_ops.txt +++ b/Documentation/local_ops.txt @@ -45,29 +45,6 @@ long fails. The definition looks like : typedef struct { atomic_long_t a; } local_t; -* Rules to follow when using local atomic operations - -- Variables touched by local ops must be per cpu variables. -- _Only_ the CPU owner of these variables must write to them. -- This CPU can use local ops from any context (process, irq, softirq, nmi, ...) - to update its local_t variables. -- Preemption (or interrupts) must be disabled when using local ops in - process context to make sure the process won't be migrated to a - different CPU between getting the per-cpu variable and doing the - actual local op. -- When using local ops in interrupt context, no special care must be - taken on a mainline kernel, since they will run on the local CPU with - preemption already disabled. I suggest, however, to explicitly - disable preemption anyway to make sure it will still work correctly on - -rt kernels. -- Reading the local cpu variable will provide the current copy of the - variable. -- Reads of these variables can be done from any CPU, because updates to - "long", aligned, variables are always atomic. Since no memory - synchronization is done by the writer CPU, an outdated copy of the - variable can be read when reading some _other_ cpu's variables. - - * Rules to follow when using local atomic operations - Variables touched by local ops must be per cpu variables.