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authorSverker Eriksson <[email protected]>2018-09-11 20:30:50 +0200
committerSverker Eriksson <[email protected]>2018-09-11 20:30:50 +0200
commite257aef202d282d37101fc0feaf1c211b055b4c0 (patch)
tree197b265d2f8ddf19bbdf4c1993fe1454c45476c4 /erts
parenta33920ef4e0669006b1c07ac7eda599ebd9583fb (diff)
parent31d26cfc44e0b0bb84879e7043db4dcf4e0e66cc (diff)
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Merge branch 'sverker/enif-cancel-select/OTP-15095'
* sverker/enif-cancel-select/OTP-15095: erts: Add ERL_NIF_SELECT_CANCEL flag for enif_select
Diffstat (limited to 'erts')
-rw-r--r--erts/doc/src/erl_nif.xml30
-rw-r--r--erts/emulator/beam/erl_drv_nif.h3
-rw-r--r--erts/emulator/beam/erl_nif.h2
-rw-r--r--erts/emulator/sys/common/erl_check_io.c78
-rw-r--r--erts/emulator/test/nif_SUITE.erl22
5 files changed, 100 insertions, 35 deletions
diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml
index a20b8ee884..a5826307f7 100644
--- a/erts/doc/src/erl_nif.xml
+++ b/erts/doc/src/erl_nif.xml
@@ -3037,7 +3037,8 @@ enif_map_iterator_destroy(env, &amp;iter);</code>
<p>Argument <c>mode</c> describes the type of events to wait for. It can be
<c>ERL_NIF_SELECT_READ</c>, <c>ERL_NIF_SELECT_WRITE</c> or a bitwise
OR combination to wait for both. It can also be <c>ERL_NIF_SELECT_STOP</c>
- which is described further below. When a read or write event is triggered,
+ or <c>ERL_NIF_SELECT_CANCEL</c> which are described further
+ below. When a read or write event is triggered,
a notification message like this is sent to the process identified by
<c>pid</c>:</p>
<code type="none">{select, Obj, Ref, ready_input | ready_output}</code>
@@ -3058,13 +3059,21 @@ enif_map_iterator_destroy(env, &amp;iter);</code>
<p>The notifications are one-shot only. To receive further notifications of the same
type (read or write), repeated calls to <c>enif_select</c> must be made
after receiving each notification.</p>
+ <p><c>ERL_NIF_SELECT_CANCEL</c> can be used to cancel previously
+ selected events. It must be used in a bitwise OR combination with
+ <c>ERL_NIF_SELECT_READ</c> and/or <c>ERL_NIF_SELECT_WRITE</c> to
+ indicate which type of event to cancel. The return value will
+ tell if the event was actualy cancelled or if a notification may
+ already have been sent.</p>
<p>Use <c>ERL_NIF_SELECT_STOP</c> as <c>mode</c> in order to safely
close an event object that has been passed to <c>enif_select</c>. The
<seealso marker="#ErlNifResourceStop"><c>stop</c></seealso> callback
of the resource <c>obj</c> will be called when it is safe to close
the event object. This safe way of closing event objects must be used
- even if all notifications have been received and no further calls to
- <c>enif_select</c> have been made.</p>
+ even if all notifications have been received (or cancelled) and no
+ further calls to <c>enif_select</c> have been made.
+ <c>ERL_NIF_SELECT_STOP</c> will first cancel any selected events
+ before it calls or schedules the <c>stop</c> callback.</p>
<p>The first call to <c>enif_select</c> for a specific OS <c>event</c> will establish
a relation between the event object and the containing resource. All subsequent calls
for an <c>event</c> must pass its containing resource as argument
@@ -3086,7 +3095,15 @@ enif_map_iterator_destroy(env, &amp;iter);</code>
<item>The stop callback was called directly by <c>enif_select</c>.</item>
<tag><c>ERL_NIF_SELECT_STOP_SCHEDULED</c></tag>
<item>The stop callback was scheduled to run on some other thread
- or later by this thread.</item>
+ or later by this thread.</item>
+ <tag><c>ERL_NIF_SELECT_READ_CANCELLED</c></tag>
+ <item>A read event was cancelled by <c>ERL_NIF_SELECT_CANCEL</c> or
+ <c>ERL_NIF_SELECT_STOP</c> and is guaranteed not to generate a
+ <c>ready_input</c> notification message.</item>
+ <tag><c>ERL_NIF_SELECT_WRITE_CANCELLED</c></tag>
+ <item>A write event was cancelled by <c>ERL_NIF_SELECT_CANCEL</c> or
+ <c>ERL_NIF_SELECT_STOP</c> and is guaranteed not to generate a
+ <c>ready_output</c> notification message.</item>
</taglist>
<p>Returns a negative value if the call failed where the following bits can be set:</p>
<taglist>
@@ -3112,6 +3129,11 @@ if (retval &amp; ERL_NIF_SELECT_STOP_CALLED) {
}
</code>
</note>
+ <note><p>The mode flag <c>ERL_NIF_SELECT_CANCEL</c> and the return flags
+ <c>ERL_NIF_SELECT_READ_CANCELLED</c> and
+ <c>ERL_NIF_SELECT_WRITE_CANCELLED</c> were introduced in erts-11.0
+ (OTP-22.0).</p>
+ </note>
</desc>
</func>
diff --git a/erts/emulator/beam/erl_drv_nif.h b/erts/emulator/beam/erl_drv_nif.h
index 31b4817fb1..9ef7c39d41 100644
--- a/erts/emulator/beam/erl_drv_nif.h
+++ b/erts/emulator/beam/erl_drv_nif.h
@@ -53,7 +53,8 @@ typedef enum {
enum ErlNifSelectFlags {
ERL_NIF_SELECT_READ = (1 << 0),
ERL_NIF_SELECT_WRITE = (1 << 1),
- ERL_NIF_SELECT_STOP = (1 << 2)
+ ERL_NIF_SELECT_STOP = (1 << 2),
+ ERL_NIF_SELECT_CANCEL = (1 << 3)
};
/*
diff --git a/erts/emulator/beam/erl_nif.h b/erts/emulator/beam/erl_nif.h
index 4c09496ef1..c5227a0c23 100644
--- a/erts/emulator/beam/erl_nif.h
+++ b/erts/emulator/beam/erl_nif.h
@@ -160,6 +160,8 @@ typedef int ErlNifEvent;
#define ERL_NIF_SELECT_STOP_SCHEDULED (1 << 1)
#define ERL_NIF_SELECT_INVALID_EVENT (1 << 2)
#define ERL_NIF_SELECT_FAILED (1 << 3)
+#define ERL_NIF_SELECT_READ_CANCELLED (1 << 4)
+#define ERL_NIF_SELECT_WRITE_CANCELLED (1 << 5)
typedef enum
{
diff --git a/erts/emulator/sys/common/erl_check_io.c b/erts/emulator/sys/common/erl_check_io.c
index 9f115706dc..f421794f91 100644
--- a/erts/emulator/sys/common/erl_check_io.c
+++ b/erts/emulator/sys/common/erl_check_io.c
@@ -916,7 +916,7 @@ enif_select(ErlNifEnv* env,
ctl_op = ERTS_POLL_OP_DEL;
}
else {
- on = 1;
+ on = !(mode & ERL_NIF_SELECT_CANCEL);
ASSERT(mode);
if (mode & ERL_DRV_READ) {
ctl_events |= ERTS_POLL_EV_IN;
@@ -1042,38 +1042,51 @@ enif_select(ErlNifEnv* env,
ret = 0;
}
else { /* off */
+ ret = 0;
if (state->type == ERTS_EV_TYPE_NIF) {
- state->driver.nif->in.pid = NIL;
- state->driver.nif->out.pid = NIL;
- }
- ASSERT(state->events==0);
- if (!wake_poller) {
- /*
- * Safe to close fd now as it is not in pollset
- * or there was no need to eject fd (kernel poll)
- */
- if (state->type == ERTS_EV_TYPE_NIF) {
- ASSERT(state->driver.stop.resource == resource);
- call_stop = CALL_STOP_AND_RELEASE;
- state->driver.stop.resource = NULL;
+ if (mode & ERL_NIF_SELECT_READ
+ && is_not_nil(state->driver.nif->in.pid)) {
+ state->driver.nif->in.pid = NIL;
+ ret |= ERL_NIF_SELECT_READ_CANCELLED;
}
- else {
- ASSERT(!state->driver.stop.resource);
- call_stop = CALL_STOP;
+ if (mode & ERL_NIF_SELECT_WRITE
+ && is_not_nil(state->driver.nif->out.pid)) {
+ state->driver.nif->out.pid = NIL;
+ ret |= ERL_NIF_SELECT_WRITE_CANCELLED;
}
- state->type = ERTS_EV_TYPE_NONE;
- ret = ERL_NIF_SELECT_STOP_CALLED;
}
- else {
- /* Not safe to close fd, postpone stop_select callback. */
- if (state->type == ERTS_EV_TYPE_NONE) {
- ASSERT(!state->driver.stop.resource);
- state->driver.stop.resource = resource;
- enif_keep_resource(resource);
+ if (mode & ERL_NIF_SELECT_STOP) {
+ ASSERT(state->events==0);
+ if (!wake_poller) {
+ /*
+ * Safe to close fd now as it is not in pollset
+ * or there was no need to eject fd (kernel poll)
+ */
+ if (state->type == ERTS_EV_TYPE_NIF) {
+ ASSERT(state->driver.stop.resource == resource);
+ call_stop = CALL_STOP_AND_RELEASE;
+ state->driver.stop.resource = NULL;
+ }
+ else {
+ ASSERT(!state->driver.stop.resource);
+ call_stop = CALL_STOP;
+ }
+ state->type = ERTS_EV_TYPE_NONE;
+ ret |= ERL_NIF_SELECT_STOP_CALLED;
+ }
+ else {
+ /* Not safe to close fd, postpone stop_select callback. */
+ if (state->type == ERTS_EV_TYPE_NONE) {
+ ASSERT(!state->driver.stop.resource);
+ state->driver.stop.resource = resource;
+ enif_keep_resource(resource);
+ }
+ state->type = ERTS_EV_TYPE_STOP_NIF;
+ ret |= ERL_NIF_SELECT_STOP_SCHEDULED;
}
- state->type = ERTS_EV_TYPE_STOP_NIF;
- ret = ERL_NIF_SELECT_STOP_SCHEDULED;
}
+ else
+ ASSERT(mode & ERL_NIF_SELECT_CANCEL);
}
done:
@@ -1251,7 +1264,8 @@ print_nif_select_op(erts_dsprintf_buf_t *dsbufp,
(int) fd,
mode & ERL_NIF_SELECT_READ ? " READ" : "",
mode & ERL_NIF_SELECT_WRITE ? " WRITE" : "",
- mode & ERL_NIF_SELECT_STOP ? " STOP" : "",
+ (mode & ERL_NIF_SELECT_STOP ? " STOP"
+ : (mode & ERL_NIF_SELECT_CANCEL ? " CANCEL" : "")),
resource->type->module,
resource->type->name,
ref);
@@ -2332,10 +2346,16 @@ drvmode2str(int mode) {
static ERTS_INLINE char *
nifmode2str(enum ErlNifSelectFlags mode) {
+ if (mode & ERL_NIF_SELECT_STOP)
+ return "STOP";
switch (mode) {
case ERL_NIF_SELECT_READ: return "READ";
case ERL_NIF_SELECT_WRITE: return "WRITE";
- case ERL_NIF_SELECT_STOP: return "STOP";
+ case ERL_NIF_SELECT_READ|ERL_NIF_SELECT_WRITE: return "READ|WRITE";
+ case ERL_NIF_SELECT_CANCEL|ERL_NIF_SELECT_READ: return "CANCEL|READ";
+ case ERL_NIF_SELECT_CANCEL|ERL_NIF_SELECT_WRITE: return "CANCEL|WRITE";
+ case ERL_NIF_SELECT_CANCEL|ERL_NIF_SELECT_READ|ERL_NIF_SELECT_WRITE:
+ return "CANCEL|READ|WRITE";
default: return "UNKNOWN";
}
}
diff --git a/erts/emulator/test/nif_SUITE.erl b/erts/emulator/test/nif_SUITE.erl
index a2f3489943..edad62a9fb 100644
--- a/erts/emulator/test/nif_SUITE.erl
+++ b/erts/emulator/test/nif_SUITE.erl
@@ -485,12 +485,14 @@ t_on_load(Config) when is_list(Config) ->
-define(ERL_NIF_SELECT_READ, (1 bsl 0)).
-define(ERL_NIF_SELECT_WRITE, (1 bsl 1)).
-define(ERL_NIF_SELECT_STOP, (1 bsl 2)).
+-define(ERL_NIF_SELECT_CANCEL, (1 bsl 3)).
-define(ERL_NIF_SELECT_STOP_CALLED, (1 bsl 0)).
-define(ERL_NIF_SELECT_STOP_SCHEDULED, (1 bsl 1)).
-define(ERL_NIF_SELECT_INVALID_EVENT, (1 bsl 2)).
-define(ERL_NIF_SELECT_FAILED, (1 bsl 3)).
-
+-define(ERL_NIF_SELECT_READ_CANCELLED, (1 bsl 4)).
+-define(ERL_NIF_SELECT_WRITE_CANCELLED, (1 bsl 5)).
select(Config) when is_list(Config) ->
ensure_lib_loaded(Config),
@@ -516,7 +518,16 @@ select(Config) when is_list(Config) ->
end),
0 = select_nif(R,?ERL_NIF_SELECT_READ,R,Pid,Ref),
{Pid, done} = receive_any(1000),
+
+ %% Cancel read
+ 0 = select_nif(R,?ERL_NIF_SELECT_READ bor ?ERL_NIF_SELECT_CANCEL,R,null,Ref),
<<"hej">> = read_nif(R, 3),
+ 0 = select_nif(R,?ERL_NIF_SELECT_READ,R,null,Ref),
+ ?ERL_NIF_SELECT_READ_CANCELLED =
+ select_nif(R,?ERL_NIF_SELECT_READ bor ?ERL_NIF_SELECT_CANCEL,R,null,Ref),
+ ok = write_nif(W, <<"hej again">>),
+ [] = flush(0),
+ <<"hej again">> = read_nif(R, 9),
%% Wait for write
Written = write_full(W, $a),
@@ -525,6 +536,15 @@ select(Config) when is_list(Config) ->
Written = read_nif(R,byte_size(Written)),
[{select, W, Ref, ready_output}] = flush(),
+ %% Cancel write
+ 0 = select_nif(W,?ERL_NIF_SELECT_WRITE bor ?ERL_NIF_SELECT_CANCEL,W,null,Ref),
+ Written2 = write_full(W, $b),
+ 0 = select_nif(W,?ERL_NIF_SELECT_WRITE,W,null,Ref),
+ ?ERL_NIF_SELECT_WRITE_CANCELLED =
+ select_nif(W,?ERL_NIF_SELECT_WRITE bor ?ERL_NIF_SELECT_CANCEL,W,null,Ref),
+ Written2 = read_nif(R,byte_size(Written2)),
+ [] = flush(0),
+
%% Close write and wait for EOF
eagain = read_nif(R, 1),
check_stop_ret(select_nif(W,?ERL_NIF_SELECT_STOP,W,null,Ref)),