| Author |
Message |
< Erlang bugs mailing list ~ erlang:monitor can hang under certain conditions |
| mickael.remond at erlang- |
 Posted: Mon Nov 21, 2005 8:22 am |
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Guest
|
Hello,
The following problem has been brought to my attention:
If this happen to be really a bug, it could trigger deadlock when using
Erlang monitor for a disappered process.
The ProcessId is a local processid, but the node has changed in the
meantime. It seems to confuse the monitor.
Here is how to reproduce it.
************ ping.erl *******************
-module(ping).
-export([start/0,loop/1]).
start() ->
register(ping,spawn(ping,loop,[initial])).
loop(X) ->
receive
{store, Y} -> loop(Y);
{retrieve, Pid} when pid(Pid) -> Pid ! X, loop(X)
end.
****************************************
First time, the Erlang monitor is not hanging:
$ erl -sname ping -s ping -detached
$ erl -sname hanger
Erlang (BEAM) emulator version 5.4.4 [source] [threads:0]
Eshell V5.4.4 (abort with ^G)
(hanger_at_louxor-erlang-fr-org)1> OldPid = spawn(io, format, ["ok",""]).
ok<0.37.0>
...
(hanger_at_louxor-erlang-fr-org)4> {ping, 'ping_at_louxor-erlang-fr-org'} !
{store, OldPid}.
{store,<0.37.0>}
(hanger_at_louxor-erlang-fr-org)5> {ping, 'ping_at_louxor-erlang-fr-org'} !
{retrieve, self()}.
{retrieve,<0.42.0>}
(hanger_at_louxor-erlang-fr-org)6> RetPid = receive X -> X end.
<0.37.0>
(hanger_at_louxor-erlang-fr-org)7> erlang:monitor(process,RetPid).
#Ref<0.0.0.68>
(hanger_at_louxor-erlang-fr-org)8> halt().
Second time:
erl -sname hanger
Erlang (BEAM) emulator version 5.4.4 [source] [threads:0]
Eshell V5.4.4 (abort with ^G)
(hanger_at_louxor-erlang-fr-org)1> {ping, 'ping_at_louxor-erlang-fr-org'} !
{retrieve, self()}.
{retrieve,<0.35.0>}
(hanger_at_louxor-erlang-fr-org)2> RetPid = receive X -> X end.
<0.37.0>
(hanger_at_louxor-erlang-fr-org)3> RetPid.
<0.37.0>
(hanger_at_louxor-erlang-fr-org)4> erlang:monitor(process,RetPid).
The function never returns.
I have started looking at the Erlang code to analyze more deeply the
problem, but I thought that it might be interesting to share the
information.
Cheers,
--
Micka |
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| mickael.remond at process |
| Posted: Mon Nov 21, 2005 8:22 am |
|
|
|
Guest
|
Hello,
The following problem has been brought to my attention:
If this happen to be really a bug, it could trigger deadlock when using
Erlang monitor for a disappered process.
The ProcessId is a local processid, but the node has changed in the
meantime. It seems to confuse the monitor.
Here is how to reproduce it.
************ ping.erl *******************
-module(ping).
-export([start/0,loop/1]).
start() ->
register(ping,spawn(ping,loop,[initial])).
loop(X) ->
receive
{store, Y} -> loop(Y);
{retrieve, Pid} when pid(Pid) -> Pid ! X, loop(X)
end.
****************************************
First time, the Erlang monitor is not hanging:
$ erl -sname ping -s ping -detached
$ erl -sname hanger
Erlang (BEAM) emulator version 5.4.4 [source] [threads:0]
Eshell V5.4.4 (abort with ^G)
(hanger_at_louxor-erlang-fr-org)1> OldPid = spawn(io, format, ["ok",""]).
ok<0.37.0>
...
(hanger_at_louxor-erlang-fr-org)4> {ping, 'ping_at_louxor-erlang-fr-org'} !
{store, OldPid}.
{store,<0.37.0>}
(hanger_at_louxor-erlang-fr-org)5> {ping, 'ping_at_louxor-erlang-fr-org'} !
{retrieve, self()}.
{retrieve,<0.42.0>}
(hanger_at_louxor-erlang-fr-org)6> RetPid = receive X -> X end.
<0.37.0>
(hanger_at_louxor-erlang-fr-org)7> erlang:monitor(process,RetPid).
#Ref<0.0.0.68>
(hanger_at_louxor-erlang-fr-org)8> halt().
Second time:
erl -sname hanger
Erlang (BEAM) emulator version 5.4.4 [source] [threads:0]
Eshell V5.4.4 (abort with ^G)
(hanger_at_louxor-erlang-fr-org)1> {ping, 'ping_at_louxor-erlang-fr-org'} !
{retrieve, self()}.
{retrieve,<0.35.0>}
(hanger_at_louxor-erlang-fr-org)2> RetPid = receive X -> X end.
<0.37.0>
(hanger_at_louxor-erlang-fr-org)3> RetPid.
<0.37.0>
(hanger_at_louxor-erlang-fr-org)4> erlang:monitor(process,RetPid).
The function never returns.
I have started looking at the Erlang code to analyze more deeply the
problem, but I thought that it might be interesting to share the
information.
Cheers,
--
Micka |
|
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| rickard.s.green at ericss |
| Posted: Mon Nov 21, 2005 8:59 am |
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|
Guest
|
Thanks, we will fix this in R10B-9.
Best Regards,
Rickard Green, Erlang/OTP
Mickael Remond wrote:
> Hello,
>
> The following problem has been brought to my attention:
> If this happen to be really a bug, it could trigger deadlock when using
> Erlang monitor for a disappered process.
> The ProcessId is a local processid, but the node has changed in the
> meantime. It seems to confuse the monitor.
>
> Here is how to reproduce it.
> ************ ping.erl *******************
> -module(ping).
> -export([start/0,loop/1]).
>
>
> start() ->
> register(ping,spawn(ping,loop,[initial])).
>
> loop(X) ->
> receive
> {store, Y} -> loop(Y);
> {retrieve, Pid} when pid(Pid) -> Pid ! X, loop(X)
> end.
> ****************************************
>
> First time, the Erlang monitor is not hanging:
> $ erl -sname ping -s ping -detached
> $ erl -sname hanger
> Erlang (BEAM) emulator version 5.4.4 [source] [threads:0]
>
> Eshell V5.4.4 (abort with ^G)
> (hanger_at_louxor-erlang-fr-org)1> OldPid = spawn(io, format, ["ok",""]).
> ok<0.37.0>
> ...
> (hanger_at_louxor-erlang-fr-org)4> {ping, 'ping_at_louxor-erlang-fr-org'} !
> {store, OldPid}.
> {store,<0.37.0>}
> (hanger_at_louxor-erlang-fr-org)5> {ping, 'ping_at_louxor-erlang-fr-org'} !
> {retrieve, self()}.
> {retrieve,<0.42.0>}
> (hanger_at_louxor-erlang-fr-org)6> RetPid = receive X -> X end.
> <0.37.0>
> (hanger_at_louxor-erlang-fr-org)7> erlang:monitor(process,RetPid).
> #Ref<0.0.0.68>
> (hanger_at_louxor-erlang-fr-org)8> halt().
>
>
> Second time:
> erl -sname hanger
> Erlang (BEAM) emulator version 5.4.4 [source] [threads:0]
> Eshell V5.4.4 (abort with ^G)
> (hanger_at_louxor-erlang-fr-org)1> {ping, 'ping_at_louxor-erlang-fr-org'} !
> {retrieve, self()}.
> {retrieve,<0.35.0>}
> (hanger_at_louxor-erlang-fr-org)2> RetPid = receive X -> X end.
> <0.37.0>
> (hanger_at_louxor-erlang-fr-org)3> RetPid.
> <0.37.0>
> (hanger_at_louxor-erlang-fr-org)4> erlang:monitor(process,RetPid).
>
> The function never returns.
>
> I have started looking at the Erlang code to analyze more deeply the
> problem, but I thought that it might be interesting to share the
> information.
>
> Cheers,
>
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