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From d3a8b4ffde38f01aa7f497d07404478b6f90041c Mon Sep 17 00:00:00 2001
From: Thomas Sanders <thomas.sanders@citrix.com>
Date: Thu, 23 Mar 2017 19:06:54 +0000
Subject: [PATCH 12/15] 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 <jgross@suse.com>
Signed-off-by: Thomas Sanders <thomas.sanders@citrix.com>
Reviewed-by: Jonathan Davies <jonathan.davies@citrix.com>
---
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 5e5a1ab..b56e3fc 100644
--- a/tools/ocaml/xenstored/process.ml
+++ b/tools/ocaml/xenstored/process.ml
@@ -350,7 +350,7 @@ 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
|
