lockfiles.lua: only check /proc/lock_pid if exists

1 files changed, 10 insertions, 5 deletions

diff --git a/lockfiles.lua b/lockfiles.lua
index 075150d..2c3cdea 100644
--- a/lockfiles.lua
+++ b/lockfiles.lua
@@ -32,11 +32,13 @@ end
 
 -- determine vis' pid
 local vis_pid
+local has_proc_fs_stat = false
 do
   local vis_proc_file = io.open('/proc/self/stat', 'r')
   if vis_proc_file then
     vis_pid = vis_proc_file:read('*n')
     vis_proc_file:close()
+    has_proc_fs_stat = true
 
   else -- fallback if /proc/self/stat is not available
     local out = capture_cmd('sh -c "echo $PPID"')
@@ -46,12 +48,15 @@ end
 assert(vis_pid)
 
 local function pid_lives(pid)
-  local tst = io.open('/proc/' .. pid .. '/stat')
-  if tst then
-    tst:close()
-    return true
+  if has_proc_fs_stat then
+    local tst = io.open('/proc/' .. pid .. '/stat')
+    if tst then
+      tst:close()
+    else
+      return false
+    end
   end
-  return false
+  return true
 end
 
 -- returns PID owning lock (possibly vis_pid)