Messages in this thread | | | Date | Wed, 31 Oct 2012 04:51:40 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 7/9] rcu: use this_cpu_ptr per-cpu helper instead of per_cpu_ptr(p, raw_smp_processor_id()) |
| |
On Wed, Oct 31, 2012 at 07:23:03PM +0800, Shan Wei wrote: > From: Shan Wei <davidshan@tencent.com> > > smp_processor_id is defined as raw_smp_processor_id. > replace per_cpu_ptr(p, raw_smp_processor_id()) is also ok. > > Signed-off-by: Shan Wei <davidshan@tencent.com>
Hello, Shan Wei,
There are several definitions of this_cpu_ptr():
0 percpu.h 63 #define this_cpu_ptr(ptr) SHIFT_PERCPU_PTR(ptr, my_cpu_offset) 1 percpu.h 65 #define this_cpu_ptr(ptr) __this_cpu_ptr(ptr) 2 percpu.h 85 #define this_cpu_ptr(ptr) per_cpu_ptr(ptr, 0)
The first uses my_cpu_offset, which is further defined in two ways:
0 percpu.h 33 #define my_cpu_offset per_cpu_offset(smp_processor_id()) 1 percpu.h 35 #define my_cpu_offset __my_cpu_offset
The first uses smp_processor_id(), which will complain if force_quiescent_state() is called with preemption disabled, which it sometimes is.
So what am I missing here?
Thanx, Paul
> --- > kernel/rcutree.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index 74df86b..3a21fcf 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -1960,7 +1960,7 @@ static void force_quiescent_state(struct rcu_state *rsp) > struct rcu_node *rnp_old = NULL; > > /* Funnel through hierarchy to reduce memory contention. */ > - rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode; > + rnp = this_cpu_ptr(rsp->rda)->mynode; > for (; rnp != NULL; rnp = rnp->parent) { > ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) || > !raw_spin_trylock(&rnp->fqslock); > -- > 1.7.1 >
| |