From ef2c41cf38a7559bbf91af42d5b6a4429db8fc68 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Wed, 5 Feb 2020 14:26:22 +0100 Subject: clone3: allow spawning processes into cgroups This adds support for creating a process in a different cgroup than its parent. Callers can limit and account processes and threads right from the moment they are spawned: - A service manager can directly spawn new services into dedicated cgroups. - A process can be directly created in a frozen cgroup and will be frozen as well. - The initial accounting jitter experienced by process supervisors and daemons is eliminated with this. - Threaded applications or even thread implementations can choose to create a specific cgroup layout where each thread is spawned directly into a dedicated cgroup. This feature is limited to the unified hierarchy. Callers need to pass a directory file descriptor for the target cgroup. The caller can choose to pass an O_PATH file descriptor. All usual migration restrictions apply, i.e. there can be no processes in inner nodes. In general, creating a process directly in a target cgroup adheres to all migration restrictions. One of the biggest advantages of this feature is that CLONE_INTO_GROUP does not need to grab the write side of the cgroup cgroup_threadgroup_rwsem. This global lock makes moving tasks/threads around super expensive. With clone3() this lock is avoided. Cc: Tejun Heo Cc: Ingo Molnar Cc: Oleg Nesterov Cc: Johannes Weiner Cc: Li Zefan Cc: Peter Zijlstra Cc: cgroups@vger.kernel.org Signed-off-by: Christian Brauner Signed-off-by: Tejun Heo --- include/uapi/linux/sched.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h index 2e3bc22c6f20..3bac0a8ceab2 100644 --- a/include/uapi/linux/sched.h +++ b/include/uapi/linux/sched.h @@ -35,6 +35,7 @@ /* Flags for the clone3() syscall. */ #define CLONE_CLEAR_SIGHAND 0x100000000ULL /* Clear any signal handler and reset to SIG_DFL. */ +#define CLONE_INTO_CGROUP 0x200000000ULL /* Clone into a specific cgroup given the right permissions. */ /* * cloning flags intersect with CSIGNAL so can be used with unshare and clone3 @@ -81,6 +82,8 @@ * @set_tid_size: This defines the size of the array referenced * in @set_tid. This cannot be larger than the * kernel's limit of nested PID namespaces. + * @cgroup: If CLONE_INTO_CGROUP is specified set this to + * a file descriptor for the cgroup. * * The structure is versioned by size and thus extensible. * New struct members must go at the end of the struct and @@ -97,11 +100,13 @@ struct clone_args { __aligned_u64 tls; __aligned_u64 set_tid; __aligned_u64 set_tid_size; + __aligned_u64 cgroup; }; #endif #define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */ #define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */ +#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */ /* * Scheduling policies -- cgit v1.2.3