removes CowCachedExecutors

[behzadnouri]

Problem

Copy-on-write semantics for cached executors can be implemented by a
simple Arc<CachedExecutors> as opposed to CowCachedExecutors:
https://github.com/solana-labs/solana/blob/f1e2598ba/runtime/src/bank.rs#L244-L247

This will also avoid the need for double locking as in:
https://github.com/solana-labs/solana/blob/f1e2598ba/runtime/src/bank.rs#L3490-L3491
https://github.com/solana-labs/solana/blob/f1e2598ba/runtime/src/bank.rs#L3525-L3526

Summary of Changes

• removed CowCachedExecutors.

[codecov]

Codecov Report

Merging #22343 (ede5b4a) into master (f1e2598) will increase coverage by 0.0%.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##           master   #22343   +/-   ##
=======================================
  Coverage    81.0%    81.0%           
=======================================
  Files         551      551           
  Lines      149806   149776   -30     
=======================================
- Hits       121476   121466   -10     
+ Misses      28330    28310   -20     

[jackcmay]

Does this prevent two bank forks from poisoning each other?

[behzadnouri]

Does this prevent two bank forks from poisoning each other?

yes, Arc::make_mut will make a clone if there are other Arc pointers to the same allocation:
https://doc.rust-lang.org/std/sync/struct.Arc.html#method.make_mut

[jackcmay]

Does this prevent two bank forks from poisoning each other?

yes, Arc::make_mut will make a clone if there are other Arc pointers to the same allocation: https://doc.rust-lang.org/std/sync/struct.Arc.html#method.make_mut

True, yeah, awesome!

[jackcmay]

Much better

[t-nelson]

lgtm! Kinda tangential to the eviction improvements we're trying to fast-track though. Should we hold off until those are in and a release cut?

[behzadnouri]

lgtm! Kinda tangential to the eviction improvements we're trying to fast-track though. Should we hold off until those are in and a release cut?

I think it makes the code simpler and might help with follow up improvements.
I will shepherd the backports not to cause any interruptions.

[behzadnouri]

lgtm! Kinda tangential to the eviction improvements we're trying to fast-track though. Should we hold off until those are in and a release cut?

I think it makes the code simpler and might help with follow up improvements. I will shepherd the backports not to cause any interruptions.

@t-nelson backports now merged in.