diff --git a/src/Command.zig b/src/Command.zig index 505fe3f85..60a898309 100644 --- a/src/Command.zig +++ b/src/Command.zig @@ -61,6 +61,8 @@ stderr: ?File = null, /// exec process takes over, such as signal handlers, setsid, setuid, etc. pre_exec: ?*const PreExecFn = null, +linux_cgroup: LinuxCgroup = linux_cgroup_default, + /// If set, then the process will be created attached to this pseudo console. /// `stdin`, `stdout`, and `stderr` will be ignored if set. pseudo_console: if (builtin.os.tag == .windows) ?windows.exp.HPCON else void = @@ -73,6 +75,11 @@ data: ?*anyopaque = null, /// Process ID is set after start is called. pid: ?posix.pid_t = null, +/// LinuxCGroup type depends on our target OS +pub const LinuxCgroup = if (builtin.os.tag == .linux) ?[]const u8 else void; +pub const linux_cgroup_default = if (LinuxCgroup == void) +{} else null; + /// The various methods a process may exit. pub const Exit = if (builtin.os.tag == .windows) union(enum) { Exited: u32, @@ -133,8 +140,16 @@ fn startPosix(self: *Command, arena: Allocator) !void { else @compileError("missing env vars"); - // Fork - const pid = try posix.fork(); + // Fork. If we have a cgroup specified on Linxu then we use clone + const pid: posix.pid_t = switch (builtin.os.tag) { + .linux => if (self.linux_cgroup) |cgroup| + try internal_os.cgroup.cloneInto(cgroup) + else + try posix.fork(), + + else => try posix.fork(), + }; + if (pid != 0) { // Parent, return immediately. self.pid = @intCast(pid); diff --git a/src/os/cgroup.zig b/src/os/cgroup.zig index aee772954..417f5641e 100644 --- a/src/os/cgroup.zig +++ b/src/os/cgroup.zig @@ -1,7 +1,11 @@ const std = @import("std"); const assert = std.debug.assert; +const linux = std.os.linux; +const posix = std.posix; const Allocator = std.mem.Allocator; +const log = std.log.scoped(.@"linux-cgroup"); + /// Returns the path to the cgroup for the given pid. pub fn current(alloc: Allocator, pid: std.os.linux.pid_t) !?[]const u8 { var buf: [std.fs.MAX_PATH_BYTES]u8 = undefined; @@ -64,6 +68,62 @@ pub fn moveInto( try file.writer().print("{}", .{pid}); } +/// Use clone3 to have the kernel create a new process with the correct cgroup +/// rather than moving the process to the correct cgroup later. +pub fn cloneInto(cgroup: []const u8) !posix.pid_t { + var buf: [std.fs.MAX_PATH_BYTES]u8 = undefined; + const path = try std.fmt.bufPrintZ(&buf, "/sys/fs/cgroup{s}", .{cgroup}); + + // Get a file descriptor that refers to the cgroup directory in the cgroup + // sysfs to pass to the kernel in clone3. + const fd: linux.fd_t = fd: { + const rc = linux.open(path, linux.O{ .PATH = true, .DIRECTORY = true }, 0); + switch (posix.errno(rc)) { + .SUCCESS => break :fd @as(linux.fd_t, @intCast(rc)), + else => |errno| { + log.err("unable to open cgroup dir {s}: {}", .{ path, errno }); + return error.CloneError; + }, + } + }; + assert(fd >= 0); + + const args: extern struct { + flags: u64, + pidfd: u64, + child_tid: u64, + parent_tid: u64, + exit_signal: u64, + stack: u64, + stack_size: u64, + tls: u64, + set_tid: u64, + set_tid_size: u64, + cgroup: u64, + } = .{ + .flags = linux.CLONE.INTO_CGROUP, + .pidfd = 0, + .child_tid = 0, + .parent_tid = 0, + .exit_signal = linux.SIG.CHLD, + .stack = 0, + .stack_size = 0, + .tls = 0, + .set_tid = 0, + .set_tid_size = 0, + .cgroup = @intCast(fd), + }; + + const rc = linux.syscall2(linux.SYS.clone3, @intFromPtr(&args), @sizeOf(@TypeOf(args))); + return switch (posix.errno(rc)) { + .SUCCESS => @as(posix.pid_t, @intCast(rc)), + else => |errno| err: { + log.err("unable to clone: {}", .{errno}); + break :err error.CloneError; + }, + }; +} + /// Returns all available cgroup controllers for the given cgroup. /// The cgroup should have a '/'-prefix. /// diff --git a/src/termio/Exec.zig b/src/termio/Exec.zig index d6342deb3..58f1a0b50 100644 --- a/src/termio/Exec.zig +++ b/src/termio/Exec.zig @@ -897,7 +897,7 @@ const Subprocess = struct { pty: ?Pty = null, command: ?Command = null, flatpak_command: ?FlatpakHostCommand = null, - linux_cgroup: termio.Options.LinuxCgroup = termio.Options.linux_cgroup_default, + linux_cgroup: Command.LinuxCgroup = Command.linux_cgroup_default, /// Initialize the subprocess. This will NOT start it, this only sets /// up the internal state necessary to start it later. @@ -1196,8 +1196,8 @@ const Subprocess = struct { // If we have a cgroup, then we copy that into our arena so the // memory remains valid when we start. - const linux_cgroup: termio.Options.LinuxCgroup = cgroup: { - const default = termio.Options.linux_cgroup_default; + const linux_cgroup: Command.LinuxCgroup = cgroup: { + const default = Command.linux_cgroup_default; if (comptime builtin.os.tag != .linux) break :cgroup default; const path = opts.linux_cgroup orelse break :cgroup default; break :cgroup try alloc.dupe(u8, path); @@ -1315,6 +1315,7 @@ const Subprocess = struct { } }).callback, .data = self, + .linux_cgroup = self.linux_cgroup, }; try cmd.start(alloc); errdefer killCommand(&cmd) catch |err| { @@ -1345,13 +1346,6 @@ const Subprocess = struct { fn childPreExec(self: *Subprocess) !void { // Setup our pty try self.pty.?.childPreExec(); - - // If we have a cgroup set, then we want to move into that cgroup. - if (comptime builtin.os.tag == .linux) { - if (self.linux_cgroup) |cgroup| { - try internal_os.cgroup.moveInto(cgroup, 0); - } - } } /// Called to notify that we exited externally so we can unset our diff --git a/src/termio/Options.zig b/src/termio/Options.zig index 079828f38..b4edb473a 100644 --- a/src/termio/Options.zig +++ b/src/termio/Options.zig @@ -4,6 +4,7 @@ const builtin = @import("builtin"); const xev = @import("xev"); const apprt = @import("../apprt.zig"); const renderer = @import("../renderer.zig"); +const Command = @import("../Command.zig"); const Config = @import("../config.zig").Config; const termio = @import("../termio.zig"); @@ -45,7 +46,4 @@ surface_mailbox: apprt.surface.Mailbox, /// The cgroup to apply to the started termio process, if able by /// the termio implementation. This only applies to Linux. -linux_cgroup: LinuxCgroup = linux_cgroup_default, - -pub const LinuxCgroup = if (builtin.os.tag == .linux) ?[]const u8 else void; -pub const linux_cgroup_default = if (LinuxCgroup == void) {} else null; +linux_cgroup: Command.LinuxCgroup = Command.linux_cgroup_default,