Messages in this thread | | | Date | Wed, 16 Jan 2008 20:48:13 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH] Revert "local_t Documentation update" |
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* Li Zefan (lizf@cn.fujitsu.com) wrote: > This reverts commit e1265205c0ee3919c3f2c750662630154c8faab2. > > It's a duplicate commit of commit 74beb9db77930be476b267ec8518a642f39a04bf, > resulting in a duplicate section. > > Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> >
Thanks, I guess it's been merged twice somehow :S
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> --- > Documentation/local_ops.txt | 23 ----------------------- > 1 files changed, 0 insertions(+), 23 deletions(-) > > diff --git a/Documentation/local_ops.txt b/Documentation/local_ops.txt > index 1a45f11..4269a11 100644 > --- a/Documentation/local_ops.txt > +++ b/Documentation/local_ops.txt > @@ -68,29 +68,6 @@ typedef struct { atomic_long_t a; } local_t; > 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. > -- _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 - synchronization is done by the writer CPU, an outdated copy of the 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. > - > - > * How to use local atomic operations > > #include <linux/percpu.h> > -- > 1.5.3.rc7 >
-- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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