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/** POSIX gettimeofday
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/** POSIX gettimeofday
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 *
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 *
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 * The time variables are memory mapped(RO) from kernel, which updates
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 * The time variables are memory mapped(RO) from kernel, which updates
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 * them periodically. As it is impossible to read 2 values atomically, we
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 * them periodically. As it is impossible to read 2 values atomically, we
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 * use a trick: First read a seconds, then read microseconds, then
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 * use a trick: First read a seconds, then read microseconds, then
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 * read seconds again. If a second elapsed in the meantime, read
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 * read seconds again. If a second elapsed in the meantime, set it to zero.
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 * useconds again. This provides assurance, that at least the
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 * This provides assurance, that at least the
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 * sequence of subsequent gettimeofday calls is ordered.
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 * sequence of subsequent gettimeofday calls is ordered.
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 */
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 */
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int gettimeofday(struct timeval *tv, struct timezone *tz)
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int gettimeofday(struct timeval *tv, struct timezone *tz)
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{
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{
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    void *mapping;
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    void *mapping;