unix: fix event port panic after close

Fixes golang/go#54363

Change-Id: I38813aefaf58ef91605e0a6e3e6622c8a39d6a8d
Reviewed-on: https://go-review.googlesource.com/c/sys/+/422338
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

unix/syscall_internal_solaris_test.go

@@ -177,3 +177,60 @@ func TestEventPortDissociateAlreadyGone(t *testing.T) {
 	// The maps should be empty and there should be no pending events
 	port.checkInternals(t, 0, 0, 0, 0)
 }
+
+// Regression test for spuriously triggering a panic about memory mismanagement
+// that can be triggered by an event processing thread trying to process an event
+// after a different thread has already called port.Close().
+// Implemented as an internal test so that we can just simulate the Close()
+// because if you call close first in the same thread, things work properly
+// anyway.
+func TestEventPortGetAfterClose(t *testing.T) {
+	port, err := NewEventPort()
+	if err != nil {
+		t.Fatalf("NewEventPort failed: %v", err)
+	}
+	// Create, associate, and delete 2 files
+	for i := 0; i < 2; i++ {
+		tmpfile, err := os.CreateTemp("", "eventport")
+		if err != nil {
+			t.Fatalf("unable to create tempfile: %v", err)
+		}
+		path := tmpfile.Name()
+		stat, err := os.Stat(path)
+		if err != nil {
+			t.Fatalf("unable to stat tempfile: %v", err)
+		}
+		err = port.AssociatePath(path, stat, FILE_MODIFIED, nil)
+		if err != nil {
+			t.Fatalf("unable to AssociatePath tempfile: %v", err)
+		}
+		err = os.Remove(path)
+		if err != nil {
+			t.Fatalf("unable to Remove tempfile: %v", err)
+		}
+	}
+	n, err := port.Pending()
+	if err != nil {
+		t.Errorf("Pending failed: %v", err)
+	}
+	if n != 2 {
+		t.Errorf("expected 2 pending events, got %d", n)
+	}
+	// Simulate a close from a different thread
+	port.fds = nil
+	port.paths = nil
+	port.cookies = nil
+	// Ensure that we get back reasonable errors rather than panic
+	_, err = port.GetOne(nil)
+	if err == nil || err.Error() != "this EventPort is already closed" {
+		t.Errorf("didn't receive expected error of 'this EventPort is already closed'; got: %v", err)
+	}
+	events := make([]PortEvent, 2)
+	n, err = port.Get(events, 1, nil)
+	if n != 0 {
+		t.Errorf("expected to get back 0 events, got %d", n)
+	}
+	if err == nil || err.Error() != "this EventPort is already closed" {
+		t.Errorf("didn't receive expected error of 'this EventPort is already closed'; got: %v", err)
+	}
+}