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Use dummy guardcond to block on empty waitset

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Cyclone DDS always returns immediately from ``dds_waitset_wait`` when
there are no entities in the waitset, but the rcl timer test implies
that the expectation is that blocks.  By adding a guard condition that
is never triggered this expectation is met.

Signed-off-by: Erik Boasson <eb@ilities.com>
This commit is contained in:
Erik Boasson 2019-08-19 16:16:57 +02:00 • committed by eboasson
parent d06953bd91
commit e4fa799090
1 changed files with 20 additions and 0 deletions
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20
rmw_cyclonedds_cpp/src/rmw_node.cpp
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@ -161,6 +161,11 @@ struct Cdds
dds_entity_t ppant; dds_entity_t ppant;
dds_entity_t builtin_readers[sizeof(builtin_topics) / sizeof(builtin_topics[0])]; dds_entity_t builtin_readers[sizeof(builtin_topics) / sizeof(builtin_topics[0])];
/* special guard condition that gets attached to every waitset but that is never triggered:
this way, we can avoid Cyclone's behaviour of always returning immediately when no
entities are attached to a waitset */
dds_entity_t gc_for_empty_waitset;
/* set of waitsets protected by lock, used to invalidate all waitsets caches when an entity is /* set of waitsets protected by lock, used to invalidate all waitsets caches when an entity is
deleted */ deleted */
std::unordered_set<CddsWaitset *> waitsets; std::unordered_set<CddsWaitset *> waitsets;
@ -326,6 +331,13 @@ static dds_entity_t ref_ppant()
return gcdds.ppant; return gcdds.ppant;
} }
if ((gcdds.gc_for_empty_waitset = dds_create_guardcondition(gcdds.ppant)) < 0) {
RMW_SET_ERROR_MSG("failed to create guardcondition for handling empty waitsets");
dds_delete(gcdds.ppant);
gcdds.ppant = 0;
return 0;
}
static_assert(sizeof(gcdds.builtin_readers) / sizeof(gcdds.builtin_readers[0]) == static_assert(sizeof(gcdds.builtin_readers) / sizeof(gcdds.builtin_readers[0]) ==
sizeof(builtin_topics) / sizeof(builtin_topics[0]), sizeof(builtin_topics) / sizeof(builtin_topics[0]),
"mismatch between array of built-in topics and array of built-in readers"); "mismatch between array of built-in topics and array of built-in readers");
@ -1392,12 +1404,20 @@ extern "C" rmw_wait_set_t * rmw_create_wait_set(rmw_context_t * context, size_t
RMW_SET_ERROR_MSG("failed to create waitset"); RMW_SET_ERROR_MSG("failed to create waitset");
goto fail_waitset; goto fail_waitset;
} }
// Attach never-triggered guard condition. As it will never be triggered, it will never be
// included in the result of dds_waitset_wait
if (dds_waitset_attach(ws->waitseth, gcdds.gc_for_empty_waitset, INTPTR_MAX) < 0) {
RMW_SET_ERROR_MSG("failed to attach dummy guard condition for blocking on empty waitset");
goto fail_attach_dummy;
}
{ {
std::lock_guard<std::mutex> lock(gcdds.lock); std::lock_guard<std::mutex> lock(gcdds.lock);
gcdds.waitsets.insert(ws); gcdds.waitsets.insert(ws);
} }
return wait_set; return wait_set;
fail_attach_dummy:
dds_delete(ws->waitseth);
fail_waitset: fail_waitset:
unref_ppant(); unref_ppant();
fail_ws: fail_ws: