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authorSverker Eriksson <[email protected]>2019-03-15 16:08:04 +0100
committerSverker Eriksson <[email protected]>2019-03-15 16:08:04 +0100
commit80f103c64904b29e2f3d880148dd5b032cae0c02 (patch)
tree9ceb7fe8c4c65204c8d7f59e7b0260c321ee7c3b /lib
parent702ef9b0fa0a9b7345e3b397f23d8a76a2ac4df2 (diff)
parent0d550c80d4f19cc432e7de056169695d436c02a0 (diff)
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Merge branch 'sverker/ets-select-fixation-owner-change-bug/OTP-15672'
* sverker/ets-select-fixation-owner-change-bug/OTP-15672: erts: Fix ets:select table fixation leak at owner change erts: Refactor common things into traverse_context_t stdlib: Clarify docs for ets:info(_, safe_fixed)
Diffstat (limited to 'lib')
-rw-r--r--lib/stdlib/doc/src/ets.xml16
-rw-r--r--lib/stdlib/test/ets_SUITE.erl60
2 files changed, 70 insertions, 6 deletions
diff --git a/lib/stdlib/doc/src/ets.xml b/lib/stdlib/doc/src/ets.xml
index d2ac6a75b1..2cb677785d 100644
--- a/lib/stdlib/doc/src/ets.xml
+++ b/lib/stdlib/doc/src/ets.xml
@@ -642,12 +642,11 @@ Error: fun containing local Erlang function calls
<p><marker id="info_2_safe_fixed_monotonic_time"/></p>
<p><c>Item=safe_fixed|safe_fixed_monotonic_time,
Value={FixationTime,Info}|false</c></p>
- <p>If the table has been fixed using
+ <p>If the table is fixed using
<seealso marker="#safe_fixtable/2">
<c>safe_fixtable/2</c></seealso>,
the call returns a tuple where <c>FixationTime</c> is the
- time when the table was first fixed by a process, which either
- is or is not one of the processes it is fixed by now.</p>
+ last time when the table changed from unfixed to fixed.</p>
<p>The format and value of <c>FixationTime</c> depends on
<c>Item</c>:</p>
<taglist>
@@ -679,8 +678,15 @@ Error: fun containing local Erlang function calls
table is fixed by now. <c>RefCount</c> is the value
of the reference counter and it keeps track of how many times
the table has been fixed by the process.</p>
- <p>If the table never has been fixed, the call returns
- <c>false</c>.</p>
+ <p>Table fixations are not limited to <seealso marker="#safe_fixtable/2">
+ <c>safe_fixtable/2</c></seealso>. Temporary fixations may also
+ be done by for example <seealso marker="#traversal">traversing
+ functions</seealso> like <c>select</c> and <c>match</c>. Such
+ table fixations are automatically released before the
+ corresponding functions returns, but they may be seen by a
+ concurrent call to
+ <c>ets:info(T,safe_fixed|safe_fixed_monotonic_time)</c>.</p>
+ <p>If the table is not fixed at all, the call returns <c>false</c>.</p>
</item>
<item>
<p><c>Item=stats, Value=tuple()</c></p>
diff --git a/lib/stdlib/test/ets_SUITE.erl b/lib/stdlib/test/ets_SUITE.erl
index 7703198c4c..8561491d50 100644
--- a/lib/stdlib/test/ets_SUITE.erl
+++ b/lib/stdlib/test/ets_SUITE.erl
@@ -56,6 +56,7 @@
-export([t_match_spec_run/1]).
-export([t_bucket_disappears/1]).
-export([t_named_select/1]).
+-export([select_fixtab_owner_change/1]).
-export([otp_5340/1]).
-export([otp_6338/1]).
-export([otp_6842_select_1000/1]).
@@ -130,7 +131,7 @@ all() ->
t_insert_list, t_test_ms, t_select_delete, t_select_replace,
t_select_replace_next_bug,
t_ets_dets, memory, t_select_reverse, t_bucket_disappears,
- t_named_select,
+ t_named_select, select_fixtab_owner_change,
select_fail, t_insert_new, t_repair_continuation,
otp_5340, otp_6338, otp_6842_select_1000, otp_7665,
select_mbuf_trapping,
@@ -249,7 +250,64 @@ t_named_select_do(Opts) ->
verify_etsmem(EtsMem).
+%% Verify select and friends release fixtab as they should
+%% even when owneship is changed between traps.
+select_fixtab_owner_change(_Config) ->
+ T = ets:new(xxx, [protected]),
+ NKeys = 2000,
+ [ets:insert(T,{K,K band 7}) || K <- lists:seq(1,NKeys)],
+ %% Buddy and Papa will ping-pong table ownership between them
+ %% and the aim is to give Buddy the table when he is
+ %% in the middle of a yielding select* call.
+ {Buddy,_} = spawn_opt(fun() -> sfoc_buddy_loop(T, 1, undefined) end,
+ [link,monitor]),
+
+ sfoc_papa_loop(T, Buddy),
+
+ receive {'DOWN', _, process, Buddy, _} -> ok end,
+ ets:delete(T),
+ ok.
+
+sfoc_buddy_loop(T, I, State0) ->
+ receive
+ {'ETS-TRANSFER', T, Papa, _} ->
+ ets:give_away(T, Papa, State0),
+ case State0 of
+ done ->
+ ok;
+ _ ->
+ State1 = sfoc_traverse(T, I, State0),
+ %% Verify no fixation left
+ {I, false} = {I, ets:info(T, safe_fixed_monotonic_time)},
+ sfoc_buddy_loop(T, I+1, State1)
+ end
+ end.
+
+sfoc_papa_loop(T, Buddy) ->
+ ets:give_away(T, Buddy, "Catch!"),
+ receive
+ {'ETS-TRANSFER', T, Buddy, State} ->
+ case State of
+ done ->
+ ok;
+ _ ->
+ sfoc_papa_loop(T, Buddy)
+ end
+ end.
+
+sfoc_traverse(T, 1, S) ->
+ ets:select(T, [{{'$1',7}, [], ['$1']}]), S;
+sfoc_traverse(T, 2, S) ->
+ 0 = ets:select_count(T, [{{'$1',7}, [], [false]}]), S;
+sfoc_traverse(T, 3, _) ->
+ Limit = ets:info(T, size) div 2,
+ {_, Continuation} = ets:select(T, [{{'$1',7}, [], ['$1']}],
+ Limit),
+ Continuation;
+sfoc_traverse(_T, 4, Continuation) ->
+ _ = ets:select(Continuation),
+ done.
%% Check ets:match_spec_run/2.
t_match_spec_run(Config) when is_list(Config) ->