From 8ed0d75c186d9da24bd6cfb85732487b17a3b054 Mon Sep 17 00:00:00 2001 From: Sverker Eriksson Date: Thu, 23 Nov 2017 15:05:34 +0100 Subject: erts: Fix erlang:monitor toward c-nodes by suppressing DOP_MONITOR_P, DOP_MONITOR_P_EXIT and DOP_DEMONITOR_P if not supported by the remote node. In 17e198d6ee60f7dec9abfed272cf4226aea44535 I changed the behavior of erlang:monitor to not raise badarg for c-nodes but instead create a monitor to only supervise the connection. But I forgot to prevent DOP_MONITOR_P and friends from being sent to the node that does not expect them. Note: We test both DFLAG_DIST_MONITOR and DFLAG_DIST_MONITOR_NAME for the node to support process monitoring. This is because erl_interface is buggy as it sets DFLAG_DIST_MONITOR without really supporting it. ToDo: Should erl_interface stop setting DFLAG_DIST_MONITOR or should we change the meaning of these flags? --- erts/doc/src/erlang.xml | 33 +++++++++++++-------------------- erts/emulator/beam/dist.c | 26 +++++++++++++++++++++++++- erts/emulator/beam/dist.h | 4 +++- erts/emulator/beam/external.c | 15 +++++++++++++++ 4 files changed, 56 insertions(+), 22 deletions(-) (limited to 'erts') diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml index 3b7b9d6a50..d78e75a91d 100644 --- a/erts/doc/src/erlang.xml +++ b/erts/doc/src/erlang.xml @@ -3358,25 +3358,6 @@ RealSystem = system + MissedSystem monitored process resides).

-

If an attempt is made to monitor a process on an older node - (where remote process monitoring is not implemented or - where remote process monitoring by registered name is not - implemented), the call fails with badarg.

- -

The format of the 'DOWN' message changed in ERTS - 5.2 (Erlang/OTP R9B) for monitoring - by registered name. Element Object of - the 'DOWN' message could in earlier versions - sometimes be the process identifier of the monitored process and sometimes - be the registered name. Now element Object is - always a tuple consisting of the registered name and - the node name. Processes on new nodes (ERTS 5.2 - or higher versions) always get 'DOWN' messages on - the new format even if they are monitoring processes on old - nodes. Processes on old nodes always get 'DOWN' - messages on the old format.

- - Monitoring a process @@ -3384,7 +3365,19 @@ RealSystem = system + MissedSystem process identified by Item, which can be a pid() (local or remote), an atom RegisteredName or a tuple {RegisteredName, Node} for a registered process, - located elsewhere.

+ located elsewhere.

+ +

Before ERTS 10.0 (OTP 21.0), monitoring a process could fail with + badarg if the monitored process resided on a primitive node + (such as erl_interface or jinterface), where remote process monitoring + is not implemented.

+

Now, such a call to monitor will instead succeed and a + monitor is created. But the monitor will only supervise the + connection. That is, a {'DOWN', _, process, _, noconnection} is + the only message that may be received, as the primitive node have no + way of reporting the status of the monitored process.

+ + Monitoring a port diff --git a/erts/emulator/beam/dist.c b/erts/emulator/beam/dist.c index ee288dc0bd..8548dbb577 100644 --- a/erts/emulator/beam/dist.c +++ b/erts/emulator/beam/dist.c @@ -877,6 +877,13 @@ erts_dsig_send_m_exit(ErtsDSigData *dsdp, Eterm watcher, Eterm watched, DeclareTmpHeapNoproc(ctl_heap,6); int res; + if (~dsdp->dep->flags & (DFLAG_DIST_MONITOR | DFLAG_DIST_MONITOR_NAME)) { + /* + * Receiver does not support DOP_MONITOR_P_EXIT (see dsig_send_monitor) + */ + return ERTS_DSIG_SEND_OK; + } + UseTmpHeapNoproc(6); ctl = TUPLE5(&ctl_heap[0], make_small(DOP_MONITOR_P_EXIT), @@ -904,6 +911,16 @@ erts_dsig_send_monitor(ErtsDSigData *dsdp, Eterm watcher, Eterm watched, DeclareTmpHeapNoproc(ctl_heap,5); int res; + if (~dsdp->dep->flags & (DFLAG_DIST_MONITOR | DFLAG_DIST_MONITOR_NAME)) { + /* + * Receiver does not support DOP_MONITOR_P. + * Just avoid sending it and by doing that reduce this monitor + * to only supervise the connection. This will work for simple c-nodes + * with a 1-to-1 relation between "Erlang process" and OS-process. + */ + return ERTS_DSIG_SEND_OK; + } + UseTmpHeapNoproc(5); ctl = TUPLE4(&ctl_heap[0], make_small(DOP_MONITOR_P), @@ -926,6 +943,13 @@ erts_dsig_send_demonitor(ErtsDSigData *dsdp, Eterm watcher, DeclareTmpHeapNoproc(ctl_heap,5); int res; + if (~dsdp->dep->flags & (DFLAG_DIST_MONITOR | DFLAG_DIST_MONITOR_NAME)) { + /* + * Receiver does not support DOP_DEMONITOR_P (see dsig_send_monitor) + */ + return ERTS_DSIG_SEND_OK; + } + UseTmpHeapNoproc(5); ctl = TUPLE4(&ctl_heap[0], make_small(DOP_DEMONITOR_P), @@ -2379,7 +2403,7 @@ erts_dist_command(Port *prt, int initial_reds) break; } ASSERT(&oq.first->data[0] <= oq.first->extp - && oq.first->extp < oq.first->ext_endp); + && oq.first->extp <= oq.first->ext_endp); size = (*send)(prt, oq.first); erts_atomic64_inc_nob(&dep->out); esdp->io.out += (Uint64) size; diff --git a/erts/emulator/beam/dist.h b/erts/emulator/beam/dist.h index a96e39be89..ea4697815f 100644 --- a/erts/emulator/beam/dist.h +++ b/erts/emulator/beam/dist.h @@ -56,7 +56,9 @@ /* Additional optimistic flags when encoding toward pending connection */ #define DFLAG_DIST_HOPEFULLY (DFLAG_NO_MAGIC \ | DFLAG_EXPORT_PTR_TAG \ - | DFLAG_BIT_BINARIES) + | DFLAG_BIT_BINARIES \ + | DFLAG_DIST_MONITOR \ + | DFLAG_DIST_MONITOR_NAME) /* All flags that should be enabled when term_to_binary/1 is used. */ #define TERM_TO_BINARY_DFLAGS (DFLAG_EXTENDED_REFERENCES \ diff --git a/erts/emulator/beam/external.c b/erts/emulator/beam/external.c index f2e6399ad7..9cc5e71afa 100644 --- a/erts/emulator/beam/external.c +++ b/erts/emulator/beam/external.c @@ -383,6 +383,21 @@ Sint erts_encode_ext_dist_header_finalize(ErtsDistOutputBuf* ob, */ ASSERT(ep[0] == SMALL_TUPLE_EXT || ep[0] == LARGE_TUPLE_EXT); + if (~dflags & (DFLAG_DIST_MONITOR | DFLAG_DIST_MONITOR_NAME) + && ep[0] == SMALL_TUPLE_EXT + && ep[1] == 4 + && ep[2] == SMALL_INTEGER_EXT + && (ep[3] == DOP_MONITOR_P || + ep[3] == DOP_MONITOR_P_EXIT || + ep[3] == DOP_DEMONITOR_P)) { + /* + * Receiver does not support process monitoring. + * Suppress monitor control msg (see erts_dsig_send_monitor) + * by converting it to an empty (tick) packet. + */ + ob->ext_endp = ob->extp; + return reds; + } if (~dflags & (DFLAG_BIT_BINARIES | DFLAG_EXPORT_PTR_TAG | DFLAG_DIST_HDR_ATOM_CACHE)) { reds = transcode_dist_obuf(ob, dep, dflags, reds); -- cgit v1.2.3