net: u64_stats_sync improvements
- Add a comment about interrupts: 6) If counter might be written by an interrupt, readers should block interrupts. - Fix a typo in sample of use. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -23,6 +23,10 @@
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* pure reads. But if they have to fetch many values, it's better to not allow
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* preemptions/interruptions to avoid many retries.
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*
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* 6) If counter might be written by an interrupt, readers should block interrupts.
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* (On UP, there is no seqcount_t protection, a reader allowing interrupts could
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* read partial values)
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*
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* Usage :
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*
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* Stats producer (writer) should use following template granted it already got
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@ -46,7 +50,7 @@
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* start = u64_stats_fetch_begin(&stats->syncp);
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* tbytes = stats->bytes64; // non atomic operation
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* tpackets = stats->packets64; // non atomic operation
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* } while (u64_stats_fetch_retry(&stats->lock, syncp));
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* } while (u64_stats_fetch_retry(&stats->syncp, start));
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*
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*
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* Example of use in drivers/net/loopback.c, using per_cpu containers,
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