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26b276660f
* Avoid unnecessary calls to ExitInformation()
ExitInformation runs a loop over the whole validator set. This is needed
in case that there are slashings or exits to be processed in a block (we
could be caching or avoid this entirely post-Electra though). This PR
removes these calls on normal state transition to this function. h/t to
@terencechain for finding out this bug.
In addition, on processing withdrawal requests and registry updates, we
kept recomputing the exit information at the same time that the state is
updated and the function that updates the state already takes care of
tracking and updating the right exit information. So this PR removes the
calls to compute this exit information on a loop. Notice that this bug
has been present even before we had a function `ExitInformation()` so I
will document here to help the reviewer
Our previous behavior is to do this in a loop
```
st, err = validators.InitiateValidatorExit(ctx, st, vIdx, validators.ExitInformation(st))
```
This is a bit problematic since `ExitInformation` loops over the whole validator set to compute the exit information (and the total active balance) and then the function `InitiateValidatorExit` actually recomputes the total active balance looping again over the whole validator set and overwriting the pointer returned by `ExitInformation`.
On the other hand, the funciton `InitiateValidatorExit` does mutate the state `st` itself. So each call to `ExitInformation(st)` may actually return a different pointer.
The function ExitInformation computes as follows
```
err := s.ReadFromEveryValidator(func(idx int, val state.ReadOnlyValidator) error {
e := val.ExitEpoch()
if e != farFutureEpoch {
if e > exitInfo.HighestExitEpoch {
exitInfo.HighestExitEpoch = e
exitInfo.Churn = 1
} else if e == exitInfo.HighestExitEpoch {
exitInfo.Churn++
}
```
So it simply increases the churn for each validator that has epoch equal to the highest exit epoch.
The function `InitiateValidatorExit` mutates this pointer in the following way
if the state is post-electra, it disregards completely this pointer and computes the highest exit epoch and updates churn inconditionally, so the pointer `exitInfo.HighestExitEpoch` will always have the right value and is not even neded to be computed before. We could even avoid the fist loop even. If the state is pre-Electra then the function itself updates correctly the exit info for the next iteration.
* Only care about exits pre-Electra
* Update beacon-chain/core/transition/transition_no_verify_sig.go
Co-authored-by: terence <terence@prysmaticlabs.com>
* Radek's review
---------
Co-authored-by: terence <terence@prysmaticlabs.com>