From a6c15fb2424148fe1247dcf0fd2186fd4b46bc4d Mon Sep 17 00:00:00 2001
From: "Yamashita, Yuu" <peek824545201@gmail.com>
Date: Thu, 19 Apr 2018 01:02:16 +0000
Subject: [PATCH] Experimental implementation to wait rehash until acquiring
 lock

For now the code is using traditional pseudo locking mechanism
based on `noclobber`.
---
 libexec/pyenv-rehash | 56 ++++++++++++++++++++++++++++++--------------
 1 file changed, 38 insertions(+), 18 deletions(-)

diff --git a/libexec/pyenv-rehash b/libexec/pyenv-rehash
index 0c822e51..b03c0d1b 100755
--- a/libexec/pyenv-rehash
+++ b/libexec/pyenv-rehash
@@ -10,29 +10,49 @@ PROTOTYPE_SHIM_PATH="${SHIM_PATH}/.pyenv-shim"
 # Create the shims directory if it doesn't already exist.
 mkdir -p "$SHIM_PATH"
 
-# Ensure only one instance of pyenv-rehash is running at a time by
-# setting the shell's `noclobber` option and attempting to write to
-# the prototype shim file. If the file already exists, print a warning
-# to stderr and exit with a non-zero status.
-set -o noclobber
-{ echo > "$PROTOTYPE_SHIM_PATH"
-} 2>| /dev/null ||
-{ if [ -w "$SHIM_PATH" ]; then
+acquire_lock() {
+  # Ensure only one instance of pyenv-rehash is running at a time by
+  # setting the shell's `noclobber` option and attempting to write to
+  # the prototype shim file. If the file already exists, print a warning
+  # to stderr and exit with a non-zero status.
+  local ret
+  set -o noclobber
+  echo > "$PROTOTYPE_SHIM_PATH" 2>| /dev/null || ret=1
+  set +o noclobber
+  [ -z "${ret}" ]
+}
+
+# If we were able to obtain a lock, register a trap to clean up the
+# prototype shim when the process exits.
+trap release_lock EXIT
+
+remove_prototype_shim() {
+  rm -f "$PROTOTYPE_SHIM_PATH"
+}
+
+release_lock() {
+  remove_prototype_shim
+}
+
+unset acquired
+for _ in $(seq "${PYENV_REHASH_LOCK_TIMEOUT:-60}"); do
+  if acquire_lock 2>/dev/null; then
+    acquired=1
+    break
+  else
+    # POSIX sleep(1) doesn't provides time precision of subsecond
+    sleep 1
+  fi
+done
+
+if [ -z "${acquired}" ]; then
+  if [ -w "$SHIM_PATH" ]; then
     echo "pyenv: cannot rehash: $PROTOTYPE_SHIM_PATH exists"
   else
     echo "pyenv: cannot rehash: $SHIM_PATH isn't writable"
   fi
   exit 1
-} >&2
-set +o noclobber
-
-# If we were able to obtain a lock, register a trap to clean up the
-# prototype shim when the process exits.
-trap remove_prototype_shim EXIT
-
-remove_prototype_shim() {
-  rm -f "$PROTOTYPE_SHIM_PATH"
-}
+fi
 
 # The prototype shim file is a script that re-execs itself, passing
 # its filename and any arguments to `pyenv exec`. This file is