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From 0412acb95ffac94d5916ee19991cc7194e55953c Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Tue, 13 Nov 2018 12:48:49 +0100
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Subject: [PATCH] core: make sure we don't throttle change signal generator
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 when a reload is pending
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Fixes: #10627
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(cherry picked from commit b8d381c47776ea0440af175cbe0c02cb743bde08)
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Resolves: #1647359
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---
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 src/core/manager.c | 64 ++++++++++++++++++++++++++++------------------
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 1 file changed, 39 insertions(+), 25 deletions(-)
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diff --git a/src/core/manager.c b/src/core/manager.c
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index a24bfcacdf..3b2fe11e87 100644
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--- a/src/core/manager.c
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+++ b/src/core/manager.c
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@@ -2074,56 +2074,70 @@ static unsigned manager_dispatch_dbus_queue(Manager *m) {
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         assert(m);
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+        /* Avoid recursion */
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         if (m->dispatching_dbus_queue)
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                 return 0;
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-        /* Anything to do at all? */
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-        if (!m->dbus_unit_queue && !m->dbus_job_queue && !m->send_reloading_done && !m->pending_reload_message)
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-                return 0;
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+        /* When we are reloading, let's not wait with generating signals, since we need to exit the manager as quickly
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+         * as we can. There's no point in throttling generation of signals in that case. */
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+        if (MANAGER_IS_RELOADING(m) || m->send_reloading_done || m->pending_reload_message)
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+                budget = (unsigned) -1; /* infinite budget in this case */
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+        else {
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+                /* Anything to do at all? */
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+                if (!m->dbus_unit_queue && !m->dbus_job_queue)
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+                        return 0;
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-        /* Do we have overly many messages queued at the moment? If so, let's not enqueue more on top, let's sit this
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-         * cycle out, and process things in a later cycle when the queues got a bit emptier. */
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-        if (manager_bus_n_queued_write(m) > MANAGER_BUS_BUSY_THRESHOLD)
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-                return 0;
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+                /* Do we have overly many messages queued at the moment? If so, let's not enqueue more on top, let's
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+                 * sit this cycle out, and process things in a later cycle when the queues got a bit emptier. */
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+                if (manager_bus_n_queued_write(m) > MANAGER_BUS_BUSY_THRESHOLD)
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+                        return 0;
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-        /* Only process a certain number of units/jobs per event loop iteration. Even if the bus queue wasn't overly
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-         * full before this call we shouldn't increase it in size too wildly in one step, and we shouldn't monopolize
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-         * CPU time with generating these messages. Note the difference in counting of this "budget" and the
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-         * "threshold" above: the "budget" is decreased only once per generated message, regardless how many
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-         * busses/direct connections it is enqueued on, while the "threshold" is applied to each queued instance of bus
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-         * message, i.e. if the same message is enqueued to five busses/direct connections it will be counted five
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-         * times. This difference in counting ("references" vs. "instances") is primarily a result of the fact that
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-         * it's easier to implement it this way, however it also reflects the thinking that the "threshold" should put
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-         * a limit on used queue memory, i.e. space, while the "budget" should put a limit on time. Also note that
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-         * the "threshold" is currently chosen much higher than the "budget". */
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-        budget = MANAGER_BUS_MESSAGE_BUDGET;
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+                /* Only process a certain number of units/jobs per event loop iteration. Even if the bus queue wasn't
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+                 * overly full before this call we shouldn't increase it in size too wildly in one step, and we
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+                 * shouldn't monopolize CPU time with generating these messages. Note the difference in counting of
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+                 * this "budget" and the "threshold" above: the "budget" is decreased only once per generated message,
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+                 * regardless how many busses/direct connections it is enqueued on, while the "threshold" is applied to
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+                 * each queued instance of bus message, i.e. if the same message is enqueued to five busses/direct
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+                 * connections it will be counted five times. This difference in counting ("references"
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+                 * vs. "instances") is primarily a result of the fact that it's easier to implement it this way,
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+                 * however it also reflects the thinking that the "threshold" should put a limit on used queue memory,
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+                 * i.e. space, while the "budget" should put a limit on time. Also note that the "threshold" is
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+                 * currently chosen much higher than the "budget". */
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+                budget = MANAGER_BUS_MESSAGE_BUDGET;
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+        }
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         m->dispatching_dbus_queue = true;
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-        while (budget > 0 && (u = m->dbus_unit_queue)) {
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+        while (budget != 0 && (u = m->dbus_unit_queue)) {
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                 assert(u->in_dbus_queue);
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                 bus_unit_send_change_signal(u);
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-                n++, budget--;
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+                n++;
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+
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+                if (budget != (unsigned) -1)
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+                        budget--;
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         }
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-        while (budget > 0 && (j = m->dbus_job_queue)) {
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+        while (budget != 0 && (j = m->dbus_job_queue)) {
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                 assert(j->in_dbus_queue);
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                 bus_job_send_change_signal(j);
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-                n++, budget--;
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+                n++;
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+
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+                if (budget != (unsigned) -1)
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+                        budget--;
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         }
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         m->dispatching_dbus_queue = false;
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-        if (budget > 0 && m->send_reloading_done) {
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+        if (m->send_reloading_done) {
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                 m->send_reloading_done = false;
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                 bus_manager_send_reloading(m, false);
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-                n++, budget--;
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+                n++;
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         }
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-        if (budget > 0 && m->pending_reload_message) {
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+        if (m->pending_reload_message) {
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                 bus_send_pending_reload_message(m);
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                 n++;
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         }