Prevent concurrent map read and write

[yilunzhang]

Just saw 2 panic cause by concurrent map read and write. This patch use sync.Map to prevent it.

Type (put an x where ever applicable)

• Bug fix: Link to the issue
• Feature (Non-breaking change)
• Feature (Breaking change)
• Documentation Improvement

Checklist

Please put an x against the checkboxes. Write a small comment explaining if its N/A (not applicable)

• Read the CONTRIBUTION guidelines.
• All the tests are passing after the introduction of new changes.
• Added tests respective to the part of code I have written.
• Added proper documentation where ever applicable (in code and README.md).
• Code has been written according to NKN-Golang-Style-Guide

Extra information

Any extra information related to this pull request.

[gdmmx]

Why traversed tp.TxLists twice? Would tp.TxLists iterator be influenced by v.CleanOrphans?
What happen if

tp.TxLists.Range( 
    func(_, v interface{}) bool {
        ......
        v.ProcessOrphans(...)
        v.CleanOrphans(nil)
        ......
        return true
    }
)

[gdmmx]

Same as above comments.

[yilunzhang]

I’m not sure. I just replaced all map call with sync.Map without any logical changes to prevent introducing additional problems. It’s better to ask @NeolBright whether we can do this.

…

On Mon, May 20, 2019 at 03:16 gdmmx ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In chain/pool/txpool.go <#503 (comment)>: > } func (tp *TxnPool) AppendTxnPool(txn *Transaction) error { - //1. process all Orphens - for _, list := range tp.TxLists { - list.ProcessOrphans(tp.processTx) - } - for _, list := range tp.TxLists { - list.CleanOrphans(nil) - } + // 1. process all Orphens + tp.TxLists.Range(func(_, v interface{}) bool { + if list, ok := v.(*NonceSortedTxs); ok { + list.ProcessOrphans(tp.processTx) + } + return true + }) + tp.TxLists.Range(func(_, v interface{}) bool { Why traversed tp.TxLists twice? Would tp.TxLists iterator be influenced by v.CleanOrphans? What happen if tp.TxLists.Range( func(_, v interface{}) bool { ...... v.ProcessOrphans(...) v.CleanOrphans(nil) ...... return true } ) — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#503?email_source=notifications&email_token=AAVJRHWV3HPGGNHPIBLLBS3PWJ277A5CNFSM4HNZCYG2YY3PNVWWK3TUL52HS4DFWFIHK3DMKJSXC5LFON2FEZLWNFSXPKTDN5WW2ZLOORPWSZGOBZCRPKI#pullrequestreview-239409065>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAVJRHSRU4OIFPZCTED5DPDPWJ277ANCNFSM4HNZCYGQ> .