Add Config Option to Limit Number of Processes

src/apprt/gtk/cgroup.zig

@@ -66,8 +66,16 @@ pub fn init(app: *App) ![]const u8 {
     // can be monitored by things like systemd-oomd to kill if needed,
     // versus an instant hard kill.
     if (app.config.@"linux-cgroup-memory-limit") |limit| {
-        try internal_os.cgroup.configureMemoryLimit(surfaces, .{
-            .high = limit,
+        try internal_os.cgroup.configureLimit(surfaces, .{
+            .memory_high = limit,
+        });
+    }
+
+    // Configure the "max" pids limit. This is a hard limit and cannot be
+    // exceeded.
+    if (app.config.@"linux-cgroup-processes-limit") |limit| {
+        try internal_os.cgroup.configureLimit(surfaces, .{
+            .pids_max = limit,
         });
     }
 

src/config/Config.zig

@@ -1276,6 +1276,13 @@ keybind: Keybinds = .{},
 /// pressure.
 @"linux-cgroup-memory-limit": ?u64 = null,
 
+/// Number of processes limit for any individual terminal process (tab, split,
+/// window, etc.). If this is unset then no limit will be set.
+///
+/// Note that this sets the "pids.max" configuration for the process number
+/// controller, which is a hard limit.
+@"linux-cgroup-processes-limit": ?u64 = null,
+
 /// If this is false, then any cgroup initialization (for linux-cgroup)
 /// will be allowed to fail and the failure is ignored. This is useful if
 /// you view cgroup isolation as a "nice to have" and not a critical resource

src/os/cgroup.zig

@@ -180,18 +180,19 @@ pub fn configureControllers(
     try file.writer().writeAll(v);
 }
 
-pub const MemoryLimit = union(enum) {
-    /// memory.high
-    high: usize,
+pub const Limit = union(enum) {
+    memory_high: usize,
+    pids_max: usize,
 };
 
-/// Configure the memory limit for the given cgroup. Use the various
-/// fields in MemoryLimit to configure a specific type of limit.
-pub fn configureMemoryLimit(cgroup: []const u8, limit: MemoryLimit) !void {
+/// Configure a limit for the given cgroup. Use the various
+/// fields in Limit to configure a specific type of limit.
+pub fn configureLimit(cgroup: []const u8, limit: Limit) !void {
     assert(cgroup[0] == '/');
 
     const filename, const size = switch (limit) {
-        .high => |v| .{ "memory.high", v },
+        .memory_high => |v| .{ "memory.high", v },
+        .pids_max => |v| .{ "pids.max", v },
     };
 
     // Open our file