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timeout fw: be robust against past _timestamp()

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_timestamp() returns CPU local values which may not be in sync with _ts
taken from another CPU. Be robust and don't produce wraparound/negative
timeout values.

Issue #3657
This commit is contained in:
Alexander Boettcher 2020-06-18 14:31:38 +02:00 committed by Norman Feske
parent 7dbf836217
commit 309597bbda
1 changed files with 7 additions and 4 deletions
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11
repos/base/src/lib/timeout/timer_connection_time.cc
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@ -166,16 +166,19 @@ Duration Timer::Connection::curr_time()
mutex_guard.destruct();
/* interpolate time difference since the last real time update */
Timestamp const ts_diff = _timestamp() - ts;
uint64_t const us_diff = _ts_to_us_ratio(ts_diff, us_to_ts_factor,
us_to_ts_factor_shift);
Timestamp const ts_current_cpu = _timestamp();
Timestamp const ts_diff = (ts_current_cpu < ts) ? 0 : ts_current_cpu - ts;
uint64_t const us_diff = _ts_to_us_ratio(ts_diff, us_to_ts_factor,
us_to_ts_factor_shift);
interpolated_time.add(Microseconds(us_diff));
} else {
Timestamp const us = elapsed_us();
Timestamp const us_diff = (us < _us) ? 0 : us - _us;
/* use remote timer instead of timestamps */
interpolated_time.add(Microseconds(elapsed_us() - _us));
interpolated_time.add(Microseconds(us_diff));
mutex_guard.destruct();
}