Re: [Libguestfs] [PATCH common 4/4] mltools: Allow waiting for killed PIDs

Add a new, optional [?wait] parameter to On_exit.kill, allowing programs to wait for a number of seconds for the subprocess to exit. --- mltools/on_exit.ml | 30 +++++++++++++++++++++--------- mltools/on_exit.mli | 14 ++++++++++++-- 2 files changed, 33 insertions(+), 11 deletions(-) diff --git a/mltools/on_exit.ml b/mltools/on_exit.ml index e8353df..cdaa83c 100644 --- a/mltools/on_exit.ml +++ b/mltools/on_exit.ml @@ -24,10 +24,10 @@ open Unix open Printf type action = - | Unlink of string (* filename *) - | Rm_rf of string (* directory *) - | Kill of int * int (* signal, pid *) - | Fn of (unit -> unit) (* generic function *) + | Unlink of string (* filename *) + | Rm_rf of string (* directory *) + | Kill of int * int * int (* wait, signal, pid *) + | Fn of (unit -> unit) (* generic function *) (* List of (priority, action). *) let actions = ref [] @@ -35,18 +35,30 @@ let actions = ref [] (* Perform a single exit action, printing any exception but * otherwise ignoring failures. *) -let do_action action = +let rec do_action action =

try match action with | Unlink file -> Unix.unlink file | Rm_rf dir -> let cmd = sprintf "rm -rf %s" (Filename.quote dir) in ignore (Tools_utils.shell_command cmd) - | Kill (signal, pid) -> - kill pid signal + | Kill (wait, signal, pid) -> + do_kill ~wait ~signal ~pid | Fn f -> f () with exn -> debug "%s" (Printexc.to_string exn) +and do_kill ~wait ~signal ~pid = + kill pid signal; + + let rec loop i = + if i > 0 then ( + let pid', _ = waitpid [ WNOHANG ] pid in + if pid' = 0 then + loop (i-1)

+ ) + in + loop wait + (* Make sure the actions are performed only once. *) let done_actions = ref false @@ -106,6 +118,6 @@ let rm_rf ?(prio = 1000) dir = register (); List.push_front (prio, Rm_rf dir) actions -let kill ?(prio = 1000) ?(signal = Sys.sigterm) pid = +let kill ?(prio = 1000) ?(wait = 0) ?(signal = Sys.sigterm) pid = register (); - List.push_front (prio, Kill (signal, pid)) actions + List.push_front (prio, Kill (wait, signal, pid)) actions diff --git a/mltools/on_exit.mli b/mltools/on_exit.mli index 910783e..dd35101 100644 --- a/mltools/on_exit.mli +++ b/mltools/on_exit.mli @@ -58,12 +58,22 @@ val unlink : ?prio:int -> string -> unit val rm_rf : ?prio:int -> string -> unit (** Recursively remove a temporary directory on exit (using [rm -rf]). *) -val kill : ?prio:int -> ?signal:int -> int -> unit +val kill : ?prio:int -> ?wait:int -> ?signal:int -> int -> unit (** Kill [PID] on exit. The signal sent defaults to [Sys.sigterm]. Use this with care since you can end up unintentionally killing another process if [PID] goes away or doesn't exist before the - program exits. *) + program exits. + + The optional [?wait] flag attempts to wait for a specified + number of seconds for the subprocess to go away. For example + using [~wait:5] will wait for up to 5 seconds. Since this + runs when virt-v2v is exiting, it is best to keep waiting times + as short as possible. Also there is no way to report errors + in the subprocess. If reliable cleanup of a subprocess is + required then this is not the correct place to do it. + + [?wait] defaults to [0] which means we do not try to wait. *) val register : unit -> unit (** Force this module to register its at_exit function and signal