Messages in this thread | | | Date | Thu, 14 Jul 2016 21:38:00 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob |
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On Thu, Jul 14, 2016 at 12:29:59PM -0700, Paul E. McKenney wrote: > On Thu, Jul 14, 2016 at 09:20:18PM +0200, Peter Zijlstra wrote: > > /** > > + * rcu_sync_sabotage() - Sabotage a fresh rcu_sync instance > > + * @rsp: Pointer to rcu_sync structure to be sabotaged > > + * > > + * Must be called after rcu_sync_init() and before first use. > > + * > > + * Ensures rcu_sync_is_idle() returns false and rcu_sync_{enter,exit}() pairs > > + * turn into NO-OPs. > > + */ > > +void rcu_sync_sabotage(struct rcu_sync *rsp) > > +{ > > + rsp->gp_count++; > > + rsp->gp_state = !GP_IDLE; > > ??? A very strange way to say GP_PENDING. A new GP_DISABLED, perhaps?
Right, so the important thing is that its not GP_IDLE, the rest doesn't really matter.
This forces rcu_sync_is_idle() to return false. The skewed gp_count ensures rcu_sync_{enter,exit}() pairs no-op.
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