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vmm_stats: attempt 4 times to vmmapi_open (during tick) to avoid a race condition :(

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This commit is contained in:
Hannes Mehnert 2018-04-26 23:55:03 +02:00
parent 2bf1b96178
commit 2764899426
1 changed files with 48 additions and 28 deletions
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76
stats/vmm_stats.ml
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@ -21,7 +21,7 @@ let my_version = `WV1
let descr = ref []
type t = {
pid_nic : (vmctx option * (int * string) list) IM.t ;
pid_nic : ((vmctx, int) result * (int * string) list) IM.t ;
pid_rusage : rusage IM.t ;
pid_vmmapi : (string * int64) list IM.t ;
nic_ifdata : ifdata String.Map.t ;
@ -40,11 +40,50 @@ let rec wrap f arg =
Logs.err (fun m -> m "exception %s" (Printexc.to_string e)) ;
None
let fill_descr ctx =
match !descr with
| [] ->
begin match wrap vmmapi_statnames ctx with
| None ->
Logs.err (fun m -> m "vmmapi_statnames failed, shouldn't happen") ;
()
| Some d ->
Logs.info (fun m -> m "descr are %a" pp_strings d) ;
descr := d
end
| ds -> Logs.info (fun m -> m "%d descr are already present" (List.length ds))
let open_vmmapi ?(retries = 4) pid =
let name = "ukvm" ^ string_of_int pid in
if retries = 0 then begin
Logs.debug (fun m -> m "(ignored 0) vmmapi_open failed for %d" pid) ;
Error 0
end else
match wrap vmmapi_open name with
| None ->
let left = max 0 (pred retries) in
Logs.warn (fun m -> m "(ignored, %d attempts left) vmmapi_open failed for %d" left pid) ;
Error left
| Some vmctx ->
Logs.info (fun m -> m "vmmapi_open succeeded for %d" pid) ;
fill_descr vmctx ;
Ok vmctx
let try_open_vmmapi pid_nic =
IM.fold (fun pid (vmctx, nics) fresh ->
let vmctx =
match vmctx with
| Ok vmctx -> Ok vmctx
| Error retries -> open_vmmapi ~retries pid
in
IM.add pid (vmctx, nics) fresh)
pid_nic IM.empty
let gather pid vmctx nics =
wrap sysctl_rusage pid,
(match vmctx with
| None -> None
| Some vmctx -> wrap vmmapi_stats vmctx),
| Error _ -> None
| Ok vmctx -> wrap vmmapi_stats vmctx),
List.fold_left (fun ifd (nic, nname) ->
match wrap sysctl_ifdata nic with
| None ->
@ -77,23 +116,10 @@ let tick t =
String.Map.union (fun _k a _b -> Some a) ifd ifds)
t.pid_nic (IM.empty, IM.empty, String.Map.empty)
in
{ t with pid_rusage ; pid_vmmapi ; nic_ifdata }
let fill_descr ctx =
match !descr with
| [] ->
begin match wrap vmmapi_statnames ctx with
| None ->
Logs.err (fun m -> m "vmmapi_statnames failed, shouldn't happen") ;
()
| Some d ->
Logs.info (fun m -> m "descr are %a" pp_strings d) ;
descr := d
end
| ds -> Logs.info (fun m -> m "%d descr are already present" (List.length ds))
let pid_nic = try_open_vmmapi t.pid_nic in
{ t with pid_rusage ; pid_vmmapi ; nic_ifdata ; pid_nic }
let add_pid t vmid pid nics =
let name = "ukvm" ^ string_of_int pid in
match wrap sysctl_ifcount () with
| None ->
Logs.err (fun m -> m "sysctl ifcount failed for %d %a" pid pp_strings nics) ;
@ -109,15 +135,9 @@ let add_pid t vmid pid nics =
List.rev acc
in
Ok (go (List.length nics) [] max_nic) >>= fun nic_ids ->
(match wrap vmmapi_open name with
| None ->
Logs.warn (fun m -> m "(ignored) vmmapi_open failed for %d" pid) ;
Ok None
| Some vmctx ->
fill_descr vmctx ;
Ok (Some vmctx)) >>= fun vmctx ->
let vmctx = open_vmmapi pid in
Logs.info (fun m -> m "adding %d %a with vmctx %b" pid pp_strings nics
(match vmctx with None -> false | Some _ -> true)) ;
(match vmctx with Error _ -> false | Ok _ -> true)) ;
let pid_nic = IM.add pid (vmctx, nic_ids) t.pid_nic
and vmid_pid = String.Map.add vmid pid t.vmid_pid
in
@ -160,8 +180,8 @@ let remove_vmid t vmid =
Logs.info (fun m -> m "removing pid %d" pid) ;
(try
match IM.find pid t.pid_nic with
| Some vmctx, _ -> ignore (wrap vmmapi_close vmctx)
| None, _ -> ()
| Ok vmctx, _ -> ignore (wrap vmmapi_close vmctx)
| Error _, _ -> ()
with
_ -> ()) ;
let pid_nic = IM.remove pid t.pid_nic