Messages in this thread | | | Date | Fri, 3 May 2013 19:04:47 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2 1/2] sched: Add cond_resched_rcu_lock() helper |
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> The key point is that I don't understand why we cannot get the effect > we are looking for with the following in sched.h (or wherever): > > static inline int cond_resched_rcu(void) > { > #if defined(CONFIG_DEBUG_ATOMIC_SLEEP) || !defined(CONFIG_PREEMPT_RCU) > rcu_read_unlock(); > cond_resched(); > rcu_read_lock(); > #endif > } > > This adds absolutely no overhead in non-debug builds of CONFIG_PREEMPT_RCU, > does the checking in debug builds, and allows voluntary preemption in > !CONFIG_PREEMPT_RCU builds. CONFIG_PROVE_RCU builds will check for an > (illegal) outer rcu_read_lock() in CONFIG_PREEMPT_RCU builds, and you > will get "scheduling while atomic" in response to an outer rcu_read_lock() > in !CONFIG_PREEMPT_RCU builds. > > It also seems to me a lot simpler. > > Does this work, or am I still missing something?
It can do quite a number of superfluous rcu_read_unlock()/lock() pairs for voluntary preemption kernels?
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