From 0d1c8342fcec1c0e2ff5ae2e460fdaf908fd2188 Mon Sep 17 00:00:00 2001
From: Martin Tournoij <martin@arp242.net>
Date: Tue, 8 Nov 2022 21:43:19 +0100
Subject: [PATCH] Remove TestInotifyNoBlockingSyscalls (#532)

This test checks if no additional OS threads are created; this was added
after the old epoll-based inotify code was removed (which would create
additional threads). It's always been a bit flaky: it currently already
runs the test twice and "fails" only if both fail.

We don't really control the Go scheduler and when it creates/destroys OS
threads, or have all that much insight in it (the "threadcreate" profile
in pprof has been broken for years). I tried to make this test a bit
more reliable a few months ago, and the run-it-twice "solution" was the
best I could come up.

It still causes some failures though; see the links below. I don't know
why it consistently fails on armle (and not e.g. arm64), but that seems
a Go thing, rather than a fsnotify thing.

I'm not sure if this test adds all that much value; I don't really
foresee a regression where we accidentally create more OS threads than
we should.

Fixes #531
Also see: https://bugs.launchpad.net/ubuntu/+source/golang-fsnotify/+bug/1971967
---
 backend_inotify_test.go | 52 -----------------------------------------
 1 file changed, 52 deletions(-)

diff --git a/backend_inotify_test.go b/backend_inotify_test.go
index f0806f0..c857291 100644
--- a/backend_inotify_test.go
+++ b/backend_inotify_test.go
@@ -5,7 +5,6 @@ package fsnotify
 
 import (
 	"errors"
-	"fmt"
 	"os"
 	"strconv"
 	"strings"
@@ -14,57 +13,6 @@ import (
 	"time"
 )
 
-// Make sure there are no additional threads being created.
-//
-// TODO: should generalize this and run for all backends.
-func TestInotifyNoBlockingSyscalls(t *testing.T) {
-	test := func() error {
-		getThreads := func() (int, error) {
-			// return pprof.Lookup("threadcreate").Count()
-			d := fmt.Sprintf("/proc/%d/task", os.Getpid())
-			ls, err := os.ReadDir(d)
-			if err != nil {
-				return 0, fmt.Errorf("reading %q: %s", d, err)
-			}
-			return len(ls), nil
-		}
-
-		w := newWatcher(t)
-		start, err := getThreads()
-		if err != nil {
-			return err
-		}
-
-		// Call readEvents a bunch of times; if this function has a blocking raw
-		// syscall, it'll create many new kthreads
-		for i := 0; i <= 60; i++ {
-			go w.readEvents()
-		}
-
-		time.Sleep(2 * time.Second)
-
-		end, err := getThreads()
-		if err != nil {
-			return err
-		}
-		if diff := end - start; diff > 0 {
-			return fmt.Errorf("Got a nonzero diff %v. starting: %v. ending: %v", diff, start, end)
-		}
-		return nil
-	}
-
-	// This test can be a bit flaky, so run it twice and consider it "failed"
-	// only if both fail.
-	err := test()
-	if err != nil {
-		time.Sleep(2 * time.Second)
-		err := test()
-		if err != nil {
-			t.Fatal(err)
-		}
-	}
-}
-
 // Ensure that the correct error is returned on overflows.
 func TestInotifyOverflow(t *testing.T) {
 	t.Parallel()
-- 
2.50.1