Fix race condition

Author: native-api

test/stubs/stub

@@ -15,25 +15,96 @@ _STUB_RESULT="${PROGRAM}_STUB_RESULT"
 _STUB_END="${PROGRAM}_STUB_END"
 _STUB_LOG="${PROGRAM}_STUB_LOG"
 
+
+STUB_LOCKFILE="${TMPDIR}/${program}-stub.lock"
+
+release_lock() {
+  rm -f "$STUB_LOCKFILE"
+  trap - EXIT
+}
+
+acquire_lock() {
+  local start=$SECONDS
+  local acquire_timeout=60
+  local acquired=
+  while (( SECONDS <= start + $acquire_timeout )); do
+  
+    set -o noclobber
+    echo -n > "$STUB_LOCKFILE" 2>/dev/null && acquired=1
+    set +o noclobber
+
+    if [[ -n $acquired ]]; then
+      trap release_lock EXIT
+      break
+    else
+      # POSIX sleep(1) doesn't provide subsecond precision, but many others do
+      sleep 0.1 2>/dev/null || sleep 1
+    fi
+  done
+  if [[ -z $acquired ]]; then
+    echo "$0: error: could not acquire stub lock in ${acquire_timeout} seconds" >&2
+    exit 2
+  done
+)
+
+acquire_lock
+
 [ -n "${!_STUB_LOG}" ] || eval "${_STUB_LOG}"="${TMPDIR}/${program}-stub-log"
+
 if test -z "${!_STUB_END}"; then echo "$program" "$@" >>"${!_STUB_LOG}"; fi
 
 [ -e "${!_STUB_PLAN}" ] || exit 1
 [ -n "${!_STUB_RUN}" ] || eval "${_STUB_RUN}"="${TMPDIR}/${program}-stub-run"
 
 
 # Initialize or load the stub run information.
+read_runfile() {
+  if test -e "${!_STUB_RUN}"; then source "${!_STUB_RUN}"; fi
+}
+write_runfile() {
+  { 
+    echo "${_STUB_INDEX}=${!_STUB_INDEX}"
+    echo "${_STUB_RESULT}=${!_STUB_RESULT}"
+  } > "${!_STUB_RUN}"
+}
+update_runfile_index() {
+  ( eval "${_STUB_INDEX}=$((${!_STUB_INDEX} + 1))"
+    write_runfile
+  )
+}
+update_runfile_result() {
+  (
+    old_result="${!_STUB_RESULT}"
+    read_runfile
+    new_result = $(( $old_result | ${!_STUB_RESULT} ))
+    eval "${_STUB_RESULT}=\$new_result"
+    write_runfile
+  )
+}
+
 eval "${_STUB_INDEX}"=1
 eval "${_STUB_RESULT}"=0
-if test -e "${!_STUB_RUN}"; then source "${!_STUB_RUN}"; fi
-
-
-# Loop over each line in the plan.
-index=0
-while IFS= read -r line; do
-  index=$(($index + 1))
-
-  if [ -z "${!_STUB_END}" ] && [ $index -eq "${!_STUB_INDEX}" ]; then
+read_runfile
+
+# !_STUB_END is set externally to trigger verification mode for `unstub'
+# Execution mode
+if [ -z "${!_STUB_END}" ]; then
+  
+  update_runfile_index
+  # Release the lock while the payload is run to allow another `stub'
+  # of the same program to run concurrently (e.g. in a pipeline).
+  # The plan file is supposed to be finalized before stubs are run
+  # so no need to hold the lock while reading it.
+  release_lock
+
+  # Loop over each line in the plan.
+  index=0
+  while IFS= read -r line; do
+    index=$(($index + 1))
+    if [ $index -ne "${!_STUB_INDEX}" ]; then
+      continue;
+    fi
+    
     # We found the plan line we're interested in.
     # Start off by assuming success.
     result=0
@@ -76,14 +147,34 @@ while IFS= read -r line; do
     else
       eval "${_STUB_RESULT}"=1
     fi
+    
+    break
+  done < "${!_STUB_PLAN}"
+
+  # If the requested index is larger than the number
+  # of lines in the plan file, we failed.
+  if [ "${!_STUB_INDEX}" -gt $index ]; then
+    eval "${_STUB_RESULT}"=1
   fi
-done < "${!_STUB_PLAN}"
 
+  # Write out the run information.
+  acquire_lock
+  update_runfile_result
+  release_lock
+ 
+  exit "$status"
 
+fi
+
+# Verification mode (`unstub')
 if [ -n "${!_STUB_END}" ]; then
+
+  # `unstub' is supposed to run after any stubs are finished
+  release_lock
+
   # If the number of lines in the plan is larger than
   # the requested index, we failed.
-  if [ $index -ge "${!_STUB_INDEX}" ]; then
+  if [ "$(wc -l "${!_STUB_PLAN}")" -ge "${!_STUB_INDEX}" ]; then
     eval "${_STUB_RESULT}"=1
   fi
   if [ "${!_STUB_RESULT}" -ne 0 ]; then
@@ -102,18 +193,4 @@ if [ -n "${!_STUB_END}" ]; then
   # Return the result.
   exit "${!_STUB_RESULT}"
 
-else
-  # If the requested index is larger than the number
-  # of lines in the plan file, we failed.
-  if [ "${!_STUB_INDEX}" -gt $index ]; then
-    eval "${_STUB_RESULT}"=1
-  fi
-
-  # Write out the run information.
-  { echo "${_STUB_INDEX}=$((${!_STUB_INDEX} + 1))"
-    echo "${_STUB_RESULT}=${!_STUB_RESULT}"
-  } > "${!_STUB_RUN}"
-
-  exit "$status"
-
 fi