[xen stable-4.4] oxenstored: allow self-conflicts

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[xen stable-4.4] oxenstored: allow self-conflicts

commit e0fb21c2bc1bde81748c887c676a3f6d9b44a770
Author:     Thomas Sanders <[hidden email]>
AuthorDate: Thu Mar 23 19:06:54 2017 +0000
Commit:     Ian Jackson <[hidden email]>
CommitDate: Wed Apr 5 15:26:38 2017 +0100

    oxenstored: allow self-conflicts
    We already avoid inter-domain conflicts but now allow intra-domain
    conflicts.  Although there are no known practical examples of a domain
    that might perform operations that conflict with its own transactions,
    this is conceivable, so here we avoid changing those semantics
    When a transaction commit fails with a conflict and we look through
    the history of commits to see which connection(s) to blame, ignore
    historical commits that were made by the same connection as the
    failing commit.
    Reported-by: Juergen Gross <[hidden email]>
    Signed-off-by: Thomas Sanders <[hidden email]>
    Reviewed-by: Jonathan Davies <[hidden email]>
 tools/ocaml/xenstored/history.ml | 3 ++-
 tools/ocaml/xenstored/process.ml | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/ocaml/xenstored/history.ml b/tools/ocaml/xenstored/history.ml
index e941e2b..4079588 100644
--- a/tools/ocaml/xenstored/history.ml
+++ b/tools/ocaml/xenstored/history.ml
@@ -60,11 +60,12 @@ let push (x: history_record) =
  | Some d -> if not (Domain.is_free_to_conflict d) then history := x :: !history
 (* Find the connections from records since commit-count [since] for which [f record] returns [true] *)
-let filter_connections ~since ~f =
+let filter_connections ~ignore ~since ~f =
  (* The "mem" call is an optimisation, to avoid calling f if we have picked con already. *)
  (* Using a hash table rather than a list is to optimise the "mem" call. *)
  List.fold_left (fun acc hist_rec ->
  if hist_rec.finish_count > since
+ && not (hist_rec.con == ignore)
  && not (Hashtbl.mem acc hist_rec.con)
  && f hist_rec
  then Hashtbl.replace acc hist_rec.con ();
diff --git a/tools/ocaml/xenstored/process.ml b/tools/ocaml/xenstored/process.ml
index 698a456..ff2ca65 100644
--- a/tools/ocaml/xenstored/process.ml
+++ b/tools/ocaml/xenstored/process.ml
@@ -344,7 +344,7 @@ let transaction_replay c t doms cons =
  then (punish hist_rec.History.con; true)
  else false
  ) in
- let guilty_cons = History.filter_connections ~since:t.Transaction.start_count ~f:judge_and_sentence in
+ let guilty_cons = History.filter_connections ~ignore:c ~since:t.Transaction.start_count ~f:judge_and_sentence in
  if Hashtbl.length guilty_cons = 0 then debug "Found no culprit for conflict in %s: must be self or not in history." con;
generated by git-patchbot for /home/xen/git/xen.git#stable-4.4

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