wrap pool logic with mutex

go.mod

@@ -21,7 +21,7 @@ require (
 	golang.org/x/crypto v0.0.0-20210322153248-0c34fe9e7dc2 // indirect
 	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
 	google.golang.org/genproto v0.0.0-20210602131652-f16073e35f0c
-	google.golang.org/grpc v1.38.0
+	google.golang.org/grpc v1.40.0
 	gopkg.in/yaml.v2 v2.4.0
 )
 

x/wasm/keeper/keeper.go

@@ -4,6 +4,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"path/filepath"
+	"sync"
 
 	"github.com/tendermint/tendermint/libs/log"
 	"golang.org/x/sync/semaphore"
@@ -36,6 +37,7 @@ type Keeper struct {
 	wasmVM              types.WasmerEngine
 	wasmReadVMPool      []types.WasmerEngine
 	wasmReadVMSemaphore *semaphore.Weighted
+	wasmReadVMMutex     *sync.Mutex
 
 	querier   types.Querier
 	msgParser types.MsgParser
@@ -98,6 +100,7 @@ func NewKeeper(
 		wasmVM:              writeWasmVM,
 		wasmReadVMPool:      wasmReadVMPool,
 		wasmReadVMSemaphore: semaphore.NewWeighted(int64(numReadVms)),
+		wasmReadVMMutex:     &sync.Mutex{},
 		accountKeeper:       accountKeeper,
 		bankKeeper:          bankKeeper,
 		treasuryKeeper:      treasuryKeeper,

x/wasm/keeper/pool.go

@@ -6,19 +6,26 @@ import (
 	"github.com/terra-money/core/x/wasm/types"
 )
 
+var n = 0
+
 func (k Keeper) getWasmVM(ctx context.Context) (types.WasmerEngine, error) {
 	err := k.wasmReadVMSemaphore.Acquire(ctx, 1)
 	if err != nil {
 		return nil, err
 	}
 
+	k.wasmReadVMMutex.Lock()
 	wasmVM := k.wasmReadVMPool[0]
 	k.wasmReadVMPool = k.wasmReadVMPool[1:]
+	k.wasmReadVMMutex.Unlock()
 
 	return wasmVM, nil
 }
 
 func (k Keeper) putWasmVM(wasmVM types.WasmerEngine) {
+	k.wasmReadVMMutex.Lock()
 	k.wasmReadVMPool = append(k.wasmReadVMPool, wasmVM)
+	k.wasmReadVMMutex.Unlock()
+
 	k.wasmReadVMSemaphore.Release(1)
 }