On Thu, 7 Jul 2022 19:08:35 GMT, Roger Riggs <rri...@openjdk.org> wrote:
> The `ProcessBuilder.pipelineStart()` implementation does not close all of the
> file descriptors it uses to create the pipeline of processes.
>
> The process calling `pipelineStart()` is creating the pipes between the
> stages.
> As each process is launched, the file descriptor is inherited by the child
> process and
> the child process `dup`s them to the respective stdin/stdout/stderr fd.
> These copies of inherited file descriptors are handled correctly.
>
> Between the launching of each Process, the file descriptor for the read-side
> of the pipe for the output of the previous process is kept open (in the
> parent process invoking `pipelineStart`). The file descriptor is correctly
> passed to the child and is dup'd to the stdin of the next process.
>
> However, the open file descriptor in the parent is not closed after it has
> been used as the input for the next Process.
> The fix is to close the fd after it has been used as the input of the next
> process.
>
> A new test verifies that after `pipelineStart` is complete, the same file
> descriptors are open for Unix Pipes as before the test.
> The test only runs on Linux using the /proc/<pid>/fd filesystem to identify
> open file descriptors.
>
> The bug fix is in `ProcessBuilder.pipelineStart` and is applicable to all
> platforms.
src/java.base/share/classes/java/lang/ProcessBuilder.java line 1301:
> 1299: if (prevOutput instanceof RedirectPipeImpl redir) {
> 1300: // Wrap the fd so it can be closed
> 1301: new Process.PipeInputStream(redir.getFd()).close();
It looks unusual to need to create a new input stream to invoke close but I
think this is okay here.
test/jdk/java/lang/ProcessBuilder/PipelineLeaksFD.java line 59:
> 57: * @requires (os.family == "linux" & !vm.musl)
> 58: * @summary file descriptor leak with ProcessBuilder.startPipeline
> 59: * @run testng PipelineLeaksFD
I wonder if this test should be /othervm, just in case there are pipes left
over from previous tests that could interfere with the list found in /proc.
-------------
PR: https://git.openjdk.org/jdk/pull/9414
