synchronize Circom prover access using a semaphore

codex/slots/proofs/backends/circomcompat.nim

@@ -9,7 +9,7 @@
 
 {.push raises: [].}
 
-import std/[sugar, atomics]
+import std/[sugar, atomics, locks]
 
 import pkg/chronos
 import pkg/taskpools
@@ -39,6 +39,7 @@ type
     backendCfg: ptr CircomBn254Cfg
     vkp*: ptr CircomKey
     taskpool: Taskpool
+    lock: ptr Lock
 
   NormalizedProofInputs*[H] {.borrow: `.`.} = distinct ProofInputs[H]
 
@@ -97,24 +98,29 @@ proc release*(self: CircomCompat) =
   if not isNil(self.vkp):
     self.vkp.unsafeAddr.release_key()
 
+  if not isNil(self.lock):
+    deinitLock(self.lock[]) # Cleanup the lock
+    dealloc(self.lock) # Free the memory
+
 proc circomProveTask(task: ptr ProveTask) {.gcsafe.} =
-  defer:
-    discard task[].signal.fireSync()
+  withLock task[].circom.lock[]:
+    defer:
+      discard task[].signal.fireSync()
 
-  var proofPtr: ptr Proof = nil
-  try:
-    if (
-      let res = task.circom.backendCfg.prove_circuit(task.ctx, proofPtr.addr)
-      res != ERR_OK
-    ) or proofPtr == nil:
-      task.success.store(false)
-      return
+    var proofPtr: ptr Proof = nil
+    try:
+      if (
+        let res = task.circom.backendCfg.prove_circuit(task.ctx, proofPtr.addr)
+        res != ERR_OK
+      ) or proofPtr == nil:
+        task.success.store(false)
+        return
 
-    copyProof(task.proof, proofPtr[])
-    task.success.store(true)
-  finally:
-    if proofPtr != nil:
-      proofPtr.addr.release_proof()
+      copyProof(task.proof, proofPtr[])
+      task.success.store(true)
+    finally:
+      if proofPtr != nil:
+        proofPtr.addr.release_proof()
 
 proc asyncProve*[H](
     self: CircomCompat, input: NormalizedProofInputs[H], proof: ptr Proof
@@ -328,9 +334,11 @@ proc init*(
     numSamples = DefaultSamplesNum,
     taskpool: Taskpool,
 ): CircomCompat =
-  ## Create a new ctx
-  ##
+  # Allocate and initialize the lock
+  var lockPtr = create(Lock) # Allocate memory for the lock
+  initLock(lockPtr[]) # Initialize the lock
 
+  ## Create a new ctx
   var cfg: ptr CircomBn254Cfg
   var zkey = if zkeyPath.len > 0: zkeyPath.cstring else: nil
 
@@ -359,4 +367,5 @@ proc init*(
     backendCfg: cfg,
     vkp: vkpPtr,
     taskpool: taskpool,
+    lock: lockPtr,
   )