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percpu-refcount: one bit is enough for REF_STATUS
percpu-refcount currently reserves two lowest bits of its percpu pointer to indicate its state; however, only one bit is used for PCPU_REF_DEAD. Simplify it by removing PCPU_STATUS_BITS/MASK and testing PCPU_REF_DEAD directly. This also allows the compiler to choose a more efficient instruction depending on the architecture. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Kent Overstreet <kmo@daterainc.com> Cc: Christoph Lameter <cl@linux-foundation.org>
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2 changed files with 2 additions and 4 deletions
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@ -88,12 +88,10 @@ static inline void percpu_ref_kill(struct percpu_ref *ref)
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return percpu_ref_kill_and_confirm(ref, NULL);
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return percpu_ref_kill_and_confirm(ref, NULL);
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}
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}
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#define PCPU_STATUS_BITS 2
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#define PCPU_STATUS_MASK ((1 << PCPU_STATUS_BITS) - 1)
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#define PCPU_REF_PTR 0
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#define PCPU_REF_PTR 0
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#define PCPU_REF_DEAD 1
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#define PCPU_REF_DEAD 1
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#define REF_STATUS(count) (((unsigned long) count) & PCPU_STATUS_MASK)
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#define REF_STATUS(count) (((unsigned long) count) & PCPU_REF_DEAD)
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/**
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/**
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* percpu_ref_get - increment a percpu refcount
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* percpu_ref_get - increment a percpu refcount
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@ -96,7 +96,7 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu)
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/* Mask out PCPU_REF_DEAD */
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/* Mask out PCPU_REF_DEAD */
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pcpu_count = (unsigned __percpu *)
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pcpu_count = (unsigned __percpu *)
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(((unsigned long) pcpu_count) & ~PCPU_STATUS_MASK);
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(((unsigned long) pcpu_count) & ~PCPU_REF_DEAD);
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for_each_possible_cpu(cpu)
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for_each_possible_cpu(cpu)
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count += *per_cpu_ptr(pcpu_count, cpu);
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count += *per_cpu_ptr(pcpu_count, cpu);
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