From 0a7533a240515c7713b8caf1eceed61d87a55006 Mon Sep 17 00:00:00 2001 From: Thomas Sanders Date: Thu, 23 Mar 2017 19:06:54 +0000 Subject: [PATCH 20/23] 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 unnecessarily. 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 Signed-off-by: Thomas Sanders Reviewed-by: Jonathan Davies --- 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 aaeb18b..4d16434 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; false ) -- 2.1.4