Drop FEATURES=cgroup, i.e., v1 cgroup usage

Remove portage's usage of Linux version 1 cgroups, which are itself
superseded by version 2 cgroups. This basically reverts
b01a1b90d8c5 ("Add FEATURES=cgroup to isolate phase processes.").

Portage's usage of version 1 cgroups has caused some issues in the
past. For example https://bugs.gentoo.org/894398, where LXD got
confused by the existence of the version 1 cgroup created by portage.

Arguably, this could be considered a bug in LXD, but with
FEATURES=pid-sandbox, as better alternative to FEATURES=cgroup
exists. And removing the code for FEATURES=cgroup reduces portage's
code size, which is also a plus.

Bug: https://bugs.gentoo.org/894398
Signed-off-by: Florian Schmaus <flow@gentoo.org>
Reviewed-by: Michał Górny <mgorny@gentoo.org>
Closes: https://github.com/gentoo/portage/pull/1057
Signed-off-by: Sam James <sam@gentoo.org>

6 files changed, 5 insertions, 170 deletions

diff --git a/NEWS b/NEWS
index 4c54ba382..82e4c8780 100644
--- a/NEWS
+++ b/NEWS
@@ -18,6 +18,11 @@ Bug fixes:
 portage-3.0.49 (2023-06-21)
 --------------
 
+Breaking changes:
+* FEATURES=cgroup was removed since it was based on version 1 cgroups, which
+  caused some issues and version 1 cgroups are obsolete. Use
+  FEATURES=pid-sandbox instead.
+
 Bug fixes:
 * Adjust write tests for DISTDIR and PORTAGE_TMPDIR to work with automount
   directories (bug #485100, bug #890812).
diff --git a/lib/_emerge/AbstractEbuildProcess.py b/lib/_emerge/AbstractEbuildProcess.py
index be257a620..97408806c 100644
--- a/lib/_emerge/AbstractEbuildProcess.py
+++ b/lib/_emerge/AbstractEbuildProcess.py
@@ -3,10 +3,7 @@
 
 import functools
 import io
-import platform
 import stat
-import subprocess
-import tempfile
 import textwrap
 from _emerge.SpawnProcess import SpawnProcess
 from _emerge.EbuildBuildDir import EbuildBuildDir
@@ -80,91 +77,6 @@ class AbstractEbuildProcess(SpawnProcess):
             self._async_wait()
             return
 
-        # Check if the cgroup hierarchy is in place. If it's not, mount it.
-        if (
-            os.geteuid() == 0
-            and platform.system() == "Linux"
-            and "cgroup" in self.settings.features
-            and self.phase not in _global_pid_phases
-        ):
-            cgroup_root = "/sys/fs/cgroup"
-            cgroup_portage = os.path.join(cgroup_root, "portage")
-
-            try:
-                # cgroup tmpfs
-                if not os.path.ismount(cgroup_root):
-                    # we expect /sys/fs to be there already
-                    if not os.path.isdir(cgroup_root):
-                        os.mkdir(cgroup_root, 0o755)
-                    subprocess.check_call(
-                        [
-                            "mount",
-                            "-t",
-                            "tmpfs",
-                            "-o",
-                            "rw,nosuid,nodev,noexec,mode=0755",
-                            "tmpfs",
-                            cgroup_root,
-                        ]
-                    )
-
-                # portage subsystem
-                if not os.path.ismount(cgroup_portage):
-                    if not os.path.isdir(cgroup_portage):
-                        os.mkdir(cgroup_portage, 0o755)
-                    subprocess.check_call(
-                        [
-                            "mount",
-                            "-t",
-                            "cgroup",
-                            "-o",
-                            "rw,nosuid,nodev,noexec,none,name=portage",
-                            "tmpfs",
-                            cgroup_portage,
-                        ]
-                    )
-                    with open(os.path.join(cgroup_portage, "release_agent"), "w") as f:
-                        f.write(
-                            os.path.join(
-                                self.settings["PORTAGE_BIN_PATH"],
-                                "cgroup-release-agent",
-                            )
-                        )
-                    with open(
-                        os.path.join(cgroup_portage, "notify_on_release"), "w"
-                    ) as f:
-                        f.write("1")
-                else:
-                    # Update release_agent if it no longer exists, because
-                    # it refers to a temporary path when portage is updating
-                    # itself.
-                    release_agent = os.path.join(cgroup_portage, "release_agent")
-                    try:
-                        with open(release_agent) as f:
-                            release_agent_path = f.readline().rstrip("\n")
-                    except OSError:
-                        release_agent_path = None
-
-                    if release_agent_path is None or not os.path.exists(
-                        release_agent_path
-                    ):
-                        with open(release_agent, "w") as f:
-                            f.write(
-                                os.path.join(
-                                    self.settings["PORTAGE_BIN_PATH"],
-                                    "cgroup-release-agent",
-                                )
-                            )
-
-                cgroup_path = tempfile.mkdtemp(
-                    dir=cgroup_portage,
-                    prefix=f"{self.settings['CATEGORY']}:{self.settings['PF']}.",
-                )
-            except (subprocess.CalledProcessError, OSError):
-                pass
-            else:
-                self.cgroup = cgroup_path
-
         if self.background:
             # Automatically prevent color codes from showing up in logs,
             # since we're not displaying to a terminal anyway.
diff --git a/lib/_emerge/SpawnProcess.py b/lib/_emerge/SpawnProcess.py
index db812a790..8f21f05c0 100644
--- a/lib/_emerge/SpawnProcess.py
+++ b/lib/_emerge/SpawnProcess.py
@@ -1,10 +1,7 @@
 # Copyright 2008-2021 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
-import errno
 import functools
-import logging
-import signal
 import sys
 
 from _emerge.SubProcess import SubProcess
@@ -12,7 +9,6 @@ import portage
 from portage import os
 from portage.const import BASH_BINARY
 from portage.output import EOutput
-from portage.util import writemsg_level
 from portage.util._async.BuildLogger import BuildLogger
 from portage.util._async.PipeLogger import PipeLogger
 from portage.util._pty import _create_pty_or_pipe
@@ -39,7 +35,6 @@ class SpawnProcess(SubProcess):
         "path_lookup",
         "pre_exec",
         "close_fds",
-        "cgroup",
         "unshare_ipc",
         "unshare_mount",
         "unshare_pid",
@@ -235,9 +230,6 @@ class SpawnProcess(SubProcess):
 
     def _unregister(self):
         SubProcess._unregister(self)
-        if self.cgroup is not None:
-            self._cgroup_cleanup()
-            self.cgroup = None
         if self._main_task is not None:
             self._main_task.done() or self._main_task.cancel()
 
@@ -249,61 +241,6 @@ class SpawnProcess(SubProcess):
                     self._main_task_cancel = None
                 self._main_task.cancel()
         SubProcess._cancel(self)
-        self._cgroup_cleanup()
-
-    def _cgroup_cleanup(self):
-        if self.cgroup:
-
-            def get_pids(cgroup):
-                try:
-                    with open(os.path.join(cgroup, "cgroup.procs")) as f:
-                        return [int(p) for p in f.read().split()]
-                except OSError:
-                    # removed by cgroup-release-agent
-                    return []
-
-            def kill_all(pids, sig):
-                for p in pids:
-                    try:
-                        os.kill(p, sig)
-                    except OSError as e:
-                        if e.errno == errno.EPERM:
-                            # Reported with hardened kernel (bug #358211).
-                            writemsg_level(
-                                f"!!! kill: ({p}) - Operation not permitted\n",
-                                level=logging.ERROR,
-                                noiselevel=-1,
-                            )
-                        elif e.errno != errno.ESRCH:
-                            raise
-
-            # step 1: kill all orphans (loop in case of new forks)
-            remaining = self._CGROUP_CLEANUP_RETRY_MAX
-            while remaining:
-                remaining -= 1
-                pids = get_pids(self.cgroup)
-                if pids:
-                    kill_all(pids, signal.SIGKILL)
-                else:
-                    break
-
-            if pids:
-                msg = []
-                msg.append(
-                    "Failed to kill pid(s) in "
-                    f"'{os.path.join(self.cgroup, 'cgroup.procs')}': "
-                    f"{' '.join(str(pid) for pid in pids)}"
-                )
-
-                self._elog("eerror", msg)
-
-            # step 2: remove the cgroup
-            try:
-                os.rmdir(self.cgroup)
-            except OSError:
-                # it may be removed already, or busy
-                # we can't do anything good about it
-                pass
 
     def _elog(self, elog_funcname, lines):
         elog_func = getattr(EOutput(), elog_funcname)
diff --git a/lib/portage/const.py b/lib/portage/const.py
index 10a208ceb..f7168d996 100644
--- a/lib/portage/const.py
+++ b/lib/portage/const.py
@@ -139,7 +139,6 @@ SUPPORTED_FEATURES = frozenset(
         "candy",
         "case-insensitive-fs",
         "ccache",
-        "cgroup",
         "chflags",
         "clean-logs",
         "collision-protect",
diff --git a/lib/portage/process.py b/lib/portage/process.py
index 4a1baedc6..63656cfbe 100644
--- a/lib/portage/process.py
+++ b/lib/portage/process.py
@@ -295,7 +295,6 @@ def spawn(
     unshare_ipc=False,
     unshare_mount=False,
     unshare_pid=False,
-    cgroup=None,
     warn_on_large_env=False,
 ):
     """
@@ -344,8 +343,6 @@ def spawn(
     @type unshare_mount: Boolean
     @param unshare_pid: If True, PID ns will be unshared from the spawned process
     @type unshare_pid: Boolean
-    @param cgroup: CGroup path to bind the process to
-    @type cgroup: String
 
     logfile requires stdout and stderr to be assigned to this process (ie not pointed
        somewhere else.)
@@ -479,7 +476,6 @@ def spawn(
                     unshare_mount,
                     unshare_pid,
                     unshare_flags,
-                    cgroup,
                 )
             except SystemExit:
                 raise
@@ -656,7 +652,6 @@ def _exec(
     unshare_mount,
     unshare_pid,
     unshare_flags,
-    cgroup,
 ):
     """
     Execute a given binary with options
@@ -694,8 +689,6 @@ def _exec(
     @type unshare_pid: Boolean
     @param unshare_flags: Flags for the unshare(2) function
     @type unshare_flags: Integer
-    @param cgroup: CGroup path to bind the process to
-    @type cgroup: String
     @rtype: None
     @return: Never returns (calls os.execve)
     """
@@ -743,13 +736,6 @@ def _exec(
 
     _setup_pipes(fd_pipes, close_fds=close_fds, inheritable=True)
 
-    # Add to cgroup
-    # it's better to do it from the child since we can guarantee
-    # it is done before we start forking children
-    if cgroup:
-        with open(os.path.join(cgroup, "cgroup.procs"), "a") as f:
-            f.write("%d\n" % portage.getpid())
-
     # Unshare (while still uid==0)
     if unshare_net or unshare_ipc or unshare_mount or unshare_pid:
         filename = find_library("c")
diff --git a/man/make.conf.5 b/man/make.conf.5
index 85ee88c05..dbab292fb 100644
--- a/man/make.conf.5
+++ b/man/make.conf.5
@@ -434,10 +434,6 @@ like "File not recognized: File truncated"), try recompiling the application
 with ccache disabled before reporting a bug. Unless you are doing development
 work, do not enable ccache.
 .TP
-.B cgroup
-Use Linux control group to control processes spawned by ebuilds. This allows
-emerge to safely kill all subprocesses when ebuild phase exits.
-.TP
 .B clean\-logs
 Enable automatic execution of the command specified by the
 PORTAGE_LOGDIR_CLEAN variable. The default PORTAGE_LOGDIR_CLEAN setting will