Messages in this thread |  | | | Date | Mon, 5 Apr 2010 11:56:24 -0700 | | From | "Paul E. McKenney" <> | | Subject | Re: [PATCH RFC tip/core/rcu 02/10] rcu: make dead code really dead |
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On Mon, Apr 05, 2010 at 02:49:28PM -0400, Mathieu Desnoyers wrote: > * Paul E. McKenney (paulmck@linux.vnet.ibm.com) wrote: > > From: Lai Jiangshan <laijs@cn.fujitsu.com> > > > > cleanup: make dead code really dead > > Is it just me or this spinlock change is more than just a cleanup ? Or > maybe it just needs a much more descriptive changelog.
Just a cleanup. In the case where the "break" could be executed, control will never reach the RCU_SAVE_DYNTICK leg of the switch statement.
That said, yes, if control -could- reach the RCU_SAVE_DYNTICK when this "break" statement was executed, we would have had a locking problem. But as it is, this change just makes the dead code really all be dead so that gcc knows not to produce the corresponding binary.
Thanx, Paul
> Thanks, > > Mathieu > > > > > Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > --- > > kernel/rcutree.c | 4 ++-- > > 1 files changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > > index e54c123..6042fb8 100644 > > --- a/kernel/rcutree.c > > +++ b/kernel/rcutree.c > > @@ -1236,11 +1236,11 @@ static void force_quiescent_state(struct rcu_state *rsp, int relaxed) > > break; /* grace period idle or initializing, ignore. */ > > > > case RCU_SAVE_DYNTICK: > > - > > - raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ > > if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) > > break; /* So gcc recognizes the dead code. */ > > > > + raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ > > + > > /* Record dyntick-idle state. */ > > force_qs_rnp(rsp, dyntick_save_progress_counter); > > raw_spin_lock(&rnp->lock); /* irqs already disabled */ > > -- > > 1.7.0 > > > > -- > Mathieu Desnoyers > Operating System Efficiency R&D Consultant > EfficiOS Inc. > http://www.efficios.com
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