[ovs-dev,v3,2/5] lib: Introduce cooperative multitasking module.

diff --git a/lib/automake.mk b/lib/automake.mk
index 0dc8a35cc..8596171c6 100644
--- a/lib/automake.mk
+++ b/lib/automake.mk
@@ -94,6 +94,9 @@  lib_libopenvswitch_la_SOURCES = \
 	lib/conntrack-other.c \
 	lib/conntrack.c \
 	lib/conntrack.h \
+	lib/cooperative-multitasking.c \
+	lib/cooperative-multitasking.h \
+	lib/cooperative-multitasking-private.h \
 	lib/coverage.c \
 	lib/coverage.h \
 	lib/cpu.c \
diff --git a/lib/cooperative-multitasking-private.h b/lib/cooperative-multitasking-private.h
new file mode 100644
index 000000000..cb8382377
--- /dev/null
+++ b/lib/cooperative-multitasking-private.h
@@ -0,0 +1,33 @@ 
+/*
+ * Copyright (c) 2024 Canonical Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef COOPERATIVE_MULTITASKING_PRIVATE_H
+#define COOPERATIVE_MULTITASKING_PRIVATE_H 1
+
+#include "openvswitch/hmap.h"
+
+extern struct hmap cooperative_multitasking_callbacks;
+
+struct cm_entry {
+    struct hmap_node node;
+    void (*cb)(void *);
+    void *arg;
+    long long int threshold;
+    long long int last_run;
+    const char *name;
+};
+
+#endif /* COOPERATIVE_MULTITASKING_PRIVATE_H */
diff --git a/lib/cooperative-multitasking.c b/lib/cooperative-multitasking.c
new file mode 100644
index 000000000..3a91af26f
--- /dev/null
+++ b/lib/cooperative-multitasking.c
@@ -0,0 +1,157 @@ 
+/*
+ * Copyright (c) 2024 Canonical Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <config.h>
+
+#include "backtrace.h"
+#include "cooperative-multitasking-private.h"
+#include "cooperative-multitasking.h"
+#include "hash.h"
+#include "openvswitch/hmap.h"
+#include "openvswitch/vlog.h"
+#include "timeval.h"
+
+VLOG_DEFINE_THIS_MODULE(cooperative_multitasking);
+
+struct hmap cooperative_multitasking_callbacks = HMAP_INITIALIZER(
+    &cooperative_multitasking_callbacks);
+
+/* Free any data allocated by calls to cooperative_multitasking_set(). */
+void
+cooperative_multitasking_destroy(void)
+{
+    struct cm_entry *cm_entry;
+    HMAP_FOR_EACH_SAFE (cm_entry, node, &cooperative_multitasking_callbacks) {
+        hmap_remove(&cooperative_multitasking_callbacks, &cm_entry->node);
+        free(cm_entry);
+    }
+}
+
+/* Set/update callback as identified by 'cb' and 'arg'.
+ *
+ * 'name' is used for logging events related to this callback.
+ *
+ * The value for 'last_run' must be updated each time the callback is run.
+ *
+ * Updating the value for 'threshold' may be necessary as a consequence of
+ * change in runtime configuration or requirements of the part of the program
+ * serviced by the callback.
+ *
+ * Providing a value of 0 for 'last_run' or 'threshold' will leave the stored
+ * value untouched. */
+void
+cooperative_multitasking_set(void (*cb)(void *), void *arg,
+                             long long int last_run, long long int threshold,
+                             const char *name)
+{
+    struct cm_entry *cm_entry;
+
+    HMAP_FOR_EACH_WITH_HASH (cm_entry, node, hash_pointer((void *) cb, 0),
+                             &cooperative_multitasking_callbacks) {
+        if (cm_entry->cb == cb && cm_entry->arg == arg) {
+            if (last_run) {
+                cm_entry->last_run = last_run;
+            }
+
+            if (threshold) {
+                cm_entry->threshold = threshold;
+            }
+            return;
+        }
+    }
+
+    cm_entry = xzalloc(sizeof *cm_entry);
+    cm_entry->cb = cb;
+    cm_entry->arg = arg;
+    cm_entry->threshold = threshold;
+    cm_entry->last_run = last_run ? last_run : time_msec();
+    cm_entry->name = name;
+
+    hmap_insert(&cooperative_multitasking_callbacks,
+                &cm_entry->node, hash_pointer((void *) cm_entry->cb, 0));
+}
+
+/* Remove callback identified by 'cb' and 'arg'. */
+void
+cooperative_multitasking_remove(void (*cb)(void *), void *arg)
+{
+    struct cm_entry *cm_entry;
+
+    HMAP_FOR_EACH_WITH_HASH (cm_entry, node, hash_pointer((void *) cb, 0),
+                             &cooperative_multitasking_callbacks) {
+        if (cm_entry->cb == cb && cm_entry->arg == arg) {
+            hmap_remove(&cooperative_multitasking_callbacks, &cm_entry->node);
+            free(cm_entry);
+            return;
+        }
+    }
+}
+
+static void
+cooperative_multitasking_yield_at__(const char *source_location)
+{
+    long long int start = time_msec();
+    struct cm_entry *cm_entry;
+    long long int elapsed;
+    bool warn;
+
+    HMAP_FOR_EACH (cm_entry, node, &cooperative_multitasking_callbacks) {
+        elapsed = time_msec() - cm_entry->last_run;
+
+        if (elapsed >= cm_entry->threshold) {
+            warn = elapsed - cm_entry->threshold > cm_entry->threshold / 8;
+
+            VLOG(warn ? VLL_WARN : VLL_DBG, "%s: yield for %s(%p): "
+                 "elapsed(%lld) >= threshold(%lld), overrun: %lld",
+                 source_location, cm_entry->name, cm_entry->arg, elapsed,
+                 cm_entry->threshold, elapsed - cm_entry->threshold);
+
+            if (warn && VLOG_IS_DBG_ENABLED()) {
+                log_backtrace();
+            }
+
+            (*cm_entry->cb)(cm_entry->arg);
+        }
+    }
+
+    elapsed = time_msec() - start;
+    if (elapsed > 1000) {
+        VLOG_WARN("Unreasonably long %lldms runtime for callbacks.", elapsed);
+    }
+}
+
+/* Iterate over registered callbacks and execute callbacks as demanded by the
+ * recorded time threshold. */
+void
+cooperative_multitasking_yield_at(const char *source_location)
+{
+    static bool yield_in_progress = false;
+
+    if (yield_in_progress) {
+        VLOG_ERR_ONCE("Nested yield avoided, this is a bug! "
+                      "Enable debug logging for more details.");
+        if (VLOG_IS_DBG_ENABLED()) {
+            VLOG_DBG("%s: nested yield.", source_location);
+            log_backtrace();
+        }
+        return;
+    }
+    yield_in_progress = true;
+
+    cooperative_multitasking_yield_at__(source_location);
+
+    yield_in_progress = false;
+}
diff --git a/lib/cooperative-multitasking.h b/lib/cooperative-multitasking.h
new file mode 100644
index 000000000..1bbb59944
--- /dev/null
+++ b/lib/cooperative-multitasking.h
@@ -0,0 +1,115 @@ 
+/*
+ * Copyright (c) 2024 Canonical Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef COOPERATIVE_MULTITASKING_H
+#define COOPERATIVE_MULTITASKING_H 1
+
+/*
+ * cooperative-multitasking, interleaved execution for Open vSwitch.
+ *
+ * Overview
+ * ========
+ *
+ * One of the goals of Open vSwitch is to be as resource efficient as
+ * possible.  Core parts of the program has been implemented as asynchronous
+ * state machines, and when absolutely necessary additional threads are used.
+ *
+ * Modules with mostly synchronous and single threaded code that are expected
+ * to have heavy processing, can make use of the cooperative-multitasking
+ * interface to yield to modules that have registered callbacks at a time
+ * threshold.
+ *
+ * Typical Usage
+ * =============
+ *
+ * The module that provides the callback typically has a run() function that is
+ * already part of the main processing loop and can then register like this:
+ *
+ * static void my_run_cb(void *arg);
+ *
+ * static void
+ * my_run(struct data *my_data)
+ * {
+ *     ...
+ *
+ *     cooperative_multitasking_set(&my_run_cb, (void *) my_data,
+ *                                  time_msec(), 1000, "my_run");
+ * }
+ *
+ * static void
+ * my_run_cb (void *arg)
+ * {
+ *     struct data *my_data = (struct data *) arg;
+ *
+ *     my_run(my_data);
+ * }
+ *
+ * static void
+ * my_destroy(struct data *my_data)
+ * {
+ *     ...
+ *
+ *     cooperatrive_multitasking_remove(&my_run_cb, (void *) my_data);
+ * }
+ *
+ * The module that is expected to have heavy processing can yield like this:
+ *
+ * HMAP_FOR_EACH (row, hmap_node, &src_table->rows) {
+ *     cooperative_multitasking_yield();
+ *
+ *     ...
+ * }
+ *
+ * Rules for implementation
+ * ========================
+ *
+ * - The module that registers itself with a callback must not use the yield
+ *   functionality inside nor should it be possible to do so via calls to other
+ *   modules.
+ *
+ * - The module that registers the callback should be self-sufficient, i.e.
+ *   the internal state of that module should not matter to the outside world,
+ *   at least it should not matter for the call stack that enters the
+ *   cooperative_multitasking_yield().
+ *
+ * - cooperative_multitasking_yield() must not be called from places that can
+ *   loop indefinitely, only in places that eventually end, otherwise it may
+ *   give a false impression that the server is working fine while it is stuck
+ *   and not actually doing any useful work.
+ *
+ * Thread-safety
+ * =============
+ *
+ * The cooperative-multitasking module and functions therein are not thread
+ * safe and must only be used by one thread.
+ */
+
+struct hmap;
+
+void cooperative_multitasking_destroy(void);
+
+void cooperative_multitasking_set(void (*cb)(void *), void *arg,
+                                  long long int last_run,
+                                  long long int threshold,
+                                  const char *name);
+
+void cooperative_multitasking_remove(void (*cb)(void *), void *arg);
+
+void cooperative_multitasking_yield_at(const char *source_location);
+#define cooperative_multitasking_yield() \
+    cooperative_multitasking_yield_at(OVS_SOURCE_LOCATOR)
+
+#endif /* COOPERATIVE_MULTITASKING_H */
diff --git a/tests/automake.mk b/tests/automake.mk
index 10c9fbb01..08c9b74d4 100644
--- a/tests/automake.mk
+++ b/tests/automake.mk
@@ -456,6 +456,7 @@  tests_ovstest_SOURCES = \
 	tests/test-ccmap.c \
 	tests/test-cmap.c \
 	tests/test-conntrack.c \
+	tests/test-cooperative-multitasking.c \
 	tests/test-csum.c \
 	tests/test-flows.c \
 	tests/test-hash.c \
diff --git a/tests/library.at b/tests/library.at
index 3f9df2f87..7b4acebb8 100644
--- a/tests/library.at
+++ b/tests/library.at
@@ -296,3 +296,13 @@  AT_CLEANUP
 AT_SETUP([uuidset module])
 AT_CHECK([ovstest test-uuidset], [0], [], [ignore])
 AT_CLEANUP
+
+AT_SETUP([cooperative-multitasking module])
+AT_CHECK([ovstest test-cooperative-multitasking], [0], [])
+AT_CLEANUP
+
+AT_SETUP([cooperative-multitasking module nested yield detection])
+AT_CHECK([ovstest test-cooperative-multitasking-nested-yield], [0], [], [dnl
+cooperative_multitasking|ERR|Nested yield avoided, this is a bug! Enable debug logging for more details.
+])
+AT_CLEANUP
diff --git a/tests/ovsdb-server.at b/tests/ovsdb-server.at
index 036e4cc3b..e152a153c 100644
--- a/tests/ovsdb-server.at
+++ b/tests/ovsdb-server.at
@@ -2845,6 +2845,7 @@  m4_define([CLEAN_LOG_FILE],
   [sed 's/[[0-9\-]]*T[[0-9:\.]]*Z|[[0-9]]*\(|.*$\)/\1/g' $1 | dnl
    sed '/|poll_loop|/d' |   dnl
    sed '/|socket_util|/d' | dnl
+   sed '/|cooperative_multitasking|DBG|/d' | dnl
    sed 's/[[0-9]]*\.ctl/<cleared>\.ctl/g'> $2])
 
 CLEAN_LOG_FILE([1.log], [1.log.clear])
diff --git a/tests/test-cooperative-multitasking.c b/tests/test-cooperative-multitasking.c
new file mode 100644
index 000000000..f7407bb03
--- /dev/null
+++ b/tests/test-cooperative-multitasking.c
@@ -0,0 +1,307 @@ 
+/*
+ * Copyright (c) 2023 Canonical Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <config.h>
+#undef NDEBUG
+#include "cooperative-multitasking.h"
+#include "cooperative-multitasking-private.h"
+#include "openvswitch/hmap.h"
+#include "ovstest.h"
+#include "timeval.h"
+#include "util.h"
+#include "openvswitch/vlog.h"
+
+struct fixture_arg {
+    bool called;
+};
+
+static void fixture_run_wrap(void *arg);
+
+#define FIXTURE_RUN_NAME "fixture_run"
+
+static void
+fixture_run(struct fixture_arg *arg)
+{
+    cooperative_multitasking_set(&fixture_run_wrap, (void *) arg,
+                                 time_msec(), 0, FIXTURE_RUN_NAME);
+    if (arg) {
+        arg->called = true;
+    }
+}
+
+static void
+fixture_run_wrap(void *arg)
+{
+    struct fixture_arg *fixture_arg = (struct fixture_arg *) arg;
+
+    fixture_run(fixture_arg);
+}
+
+
+static void fixture_other_run_wrap(void *arg);
+
+#define FIXTURE_OTHER_RUN_NAME "fixture_other_run"
+
+static void
+fixture_other_run(struct fixture_arg *arg)
+{
+    cooperative_multitasking_set(&fixture_other_run_wrap, (void *) arg,
+                                 time_msec(), 0, FIXTURE_OTHER_RUN_NAME);
+    if (arg) {
+        arg->called = true;
+    }
+}
+
+static void
+fixture_other_run_wrap(void *arg)
+{
+    struct fixture_arg *fixture_arg = (struct fixture_arg *) arg;
+
+    fixture_other_run(fixture_arg);
+}
+
+static void
+test_cm_set_registration(void)
+{
+    struct cm_entry *cm_entry;
+    struct fixture_arg arg1 = {
+        .called = false,
+    };
+    struct fixture_arg arg2 = {
+        .called = false,
+    };
+
+    timeval_stop();
+    long long int now = time_msec();
+
+    cooperative_multitasking_set(&fixture_run_wrap, (void *) &arg1, 0, 1000,
+                                 FIXTURE_RUN_NAME);
+    cooperative_multitasking_set(&fixture_run_wrap, (void *) &arg2, 0, 2000,
+                                 FIXTURE_RUN_NAME);
+    cooperative_multitasking_set(&fixture_other_run_wrap, NULL, 0, 3000,
+                                 FIXTURE_OTHER_RUN_NAME);
+
+    ovs_assert(hmap_count(&cooperative_multitasking_callbacks) == 3);
+
+    HMAP_FOR_EACH (cm_entry, node, &cooperative_multitasking_callbacks) {
+        if (cm_entry->arg == (void *) &arg1) {
+            ovs_assert(cm_entry->cb == &fixture_run_wrap);
+            ovs_assert(cm_entry->threshold == 1000);
+            ovs_assert(cm_entry->last_run == now);
+        } else if (cm_entry->arg == (void *) &arg2) {
+            ovs_assert(cm_entry->cb == &fixture_run_wrap);
+            ovs_assert(cm_entry->threshold == 2000);
+            ovs_assert(cm_entry->last_run == now);
+        } else if (cm_entry->cb == &fixture_other_run_wrap) {
+            ovs_assert(cm_entry->arg == NULL);
+            ovs_assert(cm_entry->threshold == 3000);
+            ovs_assert(cm_entry->last_run == now);
+        } else {
+            OVS_NOT_REACHED();
+        }
+    }
+
+    cooperative_multitasking_remove(&fixture_other_run_wrap, NULL);
+    ovs_assert(hmap_count(&cooperative_multitasking_callbacks) == 2);
+    cooperative_multitasking_remove(&fixture_run_wrap, (void *) &arg2);
+    ovs_assert(hmap_count(&cooperative_multitasking_callbacks) == 1);
+
+    cooperative_multitasking_destroy();
+}
+
+static void
+test_cm_set_update(void)
+{
+    struct cm_entry *cm_entry;
+    struct fixture_arg arg1 = {
+        .called = false,
+    };
+    struct fixture_arg arg2 = {
+        .called = false,
+    };
+
+    timeval_stop();
+    long long int now = time_msec();
+
+    /* First register a couple of callbacks. */
+    cooperative_multitasking_set(&fixture_run_wrap, (void *) &arg1, 0, 0,
+                                 FIXTURE_RUN_NAME);
+    cooperative_multitasking_set(&fixture_run_wrap, (void *) &arg2, 0, 0,
+                                 FIXTURE_RUN_NAME);
+
+    ovs_assert(hmap_count(&cooperative_multitasking_callbacks) == 2);
+
+    HMAP_FOR_EACH (cm_entry, node, &cooperative_multitasking_callbacks) {
+        if (cm_entry->arg == (void *) &arg1) {
+            ovs_assert(cm_entry->threshold == 0);
+            ovs_assert(cm_entry->last_run == now);
+        } else if (cm_entry->arg == (void *) &arg2) {
+            ovs_assert(cm_entry->threshold == 0);
+            ovs_assert(cm_entry->last_run == now);
+        } else {
+            OVS_NOT_REACHED();
+        }
+    }
+
+    /* Update 'last_run' and 'threshold' for each callback and validate
+     * that the correct entry was actually updated. */
+    cooperative_multitasking_set(&fixture_run_wrap, (void *) &arg1, 1, 2,
+                                 FIXTURE_RUN_NAME);
+    cooperative_multitasking_set(&fixture_run_wrap, (void *) &arg2, 3, 4,
+                                 FIXTURE_RUN_NAME);
+
+    HMAP_FOR_EACH (cm_entry, node, &cooperative_multitasking_callbacks) {
+        if (cm_entry->arg == (void *) &arg1) {
+            ovs_assert(cm_entry->threshold == 2);
+            ovs_assert(cm_entry->last_run == 1);
+        } else if (cm_entry->arg == (void *) &arg2) {
+            ovs_assert(cm_entry->threshold == 4);
+            ovs_assert(cm_entry->last_run == 3);
+        } else {
+            OVS_NOT_REACHED();
+        }
+    }
+
+    /* Confirm that providing 0 for 'last_run' or 'threshold' leaves the
+     * existing value untouched. */
+    cooperative_multitasking_set(&fixture_run_wrap, (void *) &arg1, 0, 5,
+                                 FIXTURE_RUN_NAME);
+    cooperative_multitasking_set(&fixture_run_wrap, (void *) &arg2, 6, 0,
+                                 FIXTURE_RUN_NAME);
+
+    HMAP_FOR_EACH (cm_entry, node, &cooperative_multitasking_callbacks) {
+        if (cm_entry->arg == (void *) &arg1) {
+            ovs_assert(cm_entry->threshold == 5);
+            ovs_assert(cm_entry->last_run == 1);
+        } else if (cm_entry->arg == (void *) &arg2) {
+            ovs_assert(cm_entry->threshold == 4);
+            ovs_assert(cm_entry->last_run == 6);
+        } else {
+            OVS_NOT_REACHED();
+        }
+    }
+
+    cooperative_multitasking_destroy();
+}
+
+static void
+test_cm_yield(void)
+{
+    struct cm_entry *cm_entry;
+    struct fixture_arg arg1 = {
+        .called = false,
+    };
+    struct fixture_arg arg2 = {
+        .called = false,
+    };
+
+    timeval_stop();
+    long long int now = time_msec();
+
+    /* First register a couple of callbacks. */
+    cooperative_multitasking_set(&fixture_run_wrap, (void *) &arg1, 0, 1000,
+                                 FIXTURE_RUN_NAME);
+    cooperative_multitasking_set(&fixture_run_wrap, (void *) &arg2, 0, 2000,
+                                 FIXTURE_RUN_NAME);
+
+    ovs_assert(hmap_count(&cooperative_multitasking_callbacks) == 2);
+
+    /* Call to yield should not execute callbacks until time threshold. */
+    cooperative_multitasking_yield();
+    ovs_assert(arg1.called == false);
+    ovs_assert(arg2.called == false);
+
+    HMAP_FOR_EACH (cm_entry, node, &cooperative_multitasking_callbacks) {
+        ovs_assert(cm_entry->last_run == now);
+    }
+
+    /* Move clock forward and confirm the expected callbacks to be executed. */
+    timeval_warp(1000);
+    timeval_stop();
+    cooperative_multitasking_yield();
+    ovs_assert(arg1.called == true);
+    ovs_assert(arg2.called == false);
+
+    /* Move clock forward and confirm the expected callbacks to be executed. */
+    arg1.called = arg2.called = false;
+    timeval_warp(1000);
+    timeval_stop();
+    cooperative_multitasking_yield();
+    ovs_assert(arg1.called == true);
+    ovs_assert(arg2.called == true);
+
+    cooperative_multitasking_destroy();
+}
+
+static void fixture_buggy_run_wrap(void *arg);
+
+#define FIXTURE_BUGGY_RUN_NAME "fixture_buggy_run"
+
+static void
+fixture_buggy_run(struct fixture_arg *arg)
+{
+    cooperative_multitasking_set(&fixture_buggy_run_wrap, (void *) arg,
+                                 time_msec(), 0, FIXTURE_BUGGY_RUN_NAME);
+    if (arg) {
+        arg->called = true;
+    }
+    /* A real run function MUST NOT directly or indirectly call yield, this is
+     * here to test the detection of such a programming error. */
+    cooperative_multitasking_yield();
+}
+
+static void
+fixture_buggy_run_wrap(void *arg)
+{
+    struct fixture_arg *fixture_arg = (struct fixture_arg *) arg;
+
+    fixture_buggy_run(fixture_arg);
+}
+
+static void
+test_cooperative_multitasking_nested_yield(int argc OVS_UNUSED, char *argv[])
+{
+    struct fixture_arg arg1 = {
+        .called = false,
+    };
+
+    set_program_name(argv[0]);
+    vlog_set_pattern(VLF_CONSOLE, "%c|%p|%m");
+    vlog_set_levels(NULL, VLF_SYSLOG, VLL_OFF);
+
+    time_msec(); /* Ensure timeval is initialized. */
+
+    cooperative_multitasking_set(&fixture_buggy_run_wrap, (void *) &arg1,
+                                 0, 1000, FIXTURE_BUGGY_RUN_NAME);
+    timeval_warp(1000);
+    cooperative_multitasking_yield();
+    cooperative_multitasking_destroy();
+}
+
+static void
+test_cooperative_multitasking(int argc OVS_UNUSED, char *argv[] OVS_UNUSED)
+{
+    time_msec(); /* Ensure timeval is initialized. */
+
+    test_cm_set_registration();
+    test_cm_set_update();
+    test_cm_yield();
+}
+
+OVSTEST_REGISTER("test-cooperative-multitasking",
+                 test_cooperative_multitasking);
+OVSTEST_REGISTER("test-cooperative-multitasking-nested-yield",
+                 test_cooperative_multitasking_nested_yield);