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rcu: Add READ_ONCE() to rcu_do_batch() access to rcu_divisor
Given that sysfs can change the value of rcu_divisor at any time, this commit adds a READ_ONCE to the sole access to that variable. While in the area, this commit also adds bounds checking, clamping the value to a shift that makes sense for a signed long. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
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1 changed files with 4 additions and 1 deletions
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@ -2362,6 +2362,7 @@ int rcutree_dead_cpu(unsigned int cpu)
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*/
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static void rcu_do_batch(struct rcu_data *rdp)
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{
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int div;
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unsigned long flags;
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const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
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rcu_segcblist_is_offloaded(&rdp->cblist);
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@ -2390,7 +2391,9 @@ static void rcu_do_batch(struct rcu_data *rdp)
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rcu_nocb_lock(rdp);
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WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
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pending = rcu_segcblist_n_cbs(&rdp->cblist);
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bl = max(rdp->blimit, pending >> rcu_divisor);
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div = READ_ONCE(rcu_divisor);
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div = div < 0 ? 7 : div > sizeof(long) * 8 - 2 ? sizeof(long) * 8 - 2 : div;
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bl = max(rdp->blimit, pending >> div);
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if (unlikely(bl > 100))
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tlimit = local_clock() + rcu_resched_ns;
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trace_rcu_batch_start(rcu_state.name,
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