From f1a8b69808777aff37c036fd94a0275873d12407 Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Thu, 23 Feb 2023 07:31:01 +0900
Subject: [PATCH] sd-event: always initialize sd_event.perturb

If the boot ID cannot be obtained, let's first fallback to the machine
ID, and if still cannot, then let's use 0.
Otherwise, no timer event source cannot be triggered.

Fixes #26549.

(cherry picked from commit 6d2326e036ceed30f9ccdb0266713c10a44dcf6c)
(cherry picked from commit 58c821af607b61738b7b72ad1452e70f648689a6)
(cherry picked from commit 78976199b2e016600c3f7cf8f39747c9ef6c853b)
(cherry picked from commit ac04d804c30f519918866fb4eeb3bc4a9cbadd43)
---
 src/libsystemd/sd-event/sd-event.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/src/libsystemd/sd-event/sd-event.c b/src/libsystemd/sd-event/sd-event.c
index 89accdce00..37565b17be 100644
--- a/src/libsystemd/sd-event/sd-event.c
+++ b/src/libsystemd/sd-event/sd-event.c
@@ -1126,22 +1126,21 @@ _public_ int sd_event_add_io(
 }
 
 static void initialize_perturb(sd_event *e) {
-        sd_id128_t bootid = {};
+        sd_id128_t id = {};
 
-        /* When we sleep for longer, we try to realign the wakeup to
-           the same time within each minute/second/250ms, so that
-           events all across the system can be coalesced into a single
-           CPU wakeup. However, let's take some system-specific
-           randomness for this value, so that in a network of systems
-           with synced clocks timer events are distributed a
-           bit. Here, we calculate a perturbation usec offset from the
-           boot ID. */
+        /* When we sleep for longer, we try to realign the wakeup to the same time within each
+         * minute/second/250ms, so that events all across the system can be coalesced into a single CPU
+         * wakeup. However, let's take some system-specific randomness for this value, so that in a network
+         * of systems with synced clocks timer events are distributed a bit. Here, we calculate a
+         * perturbation usec offset from the boot ID (or machine ID if failed, e.g. /proc is not mounted). */
 
         if (_likely_(e->perturb != USEC_INFINITY))
                 return;
 
-        if (sd_id128_get_boot(&bootid) >= 0)
-                e->perturb = (bootid.qwords[0] ^ bootid.qwords[1]) % USEC_PER_MINUTE;
+        if (sd_id128_get_boot(&id) >= 0 || sd_id128_get_machine(&id) > 0)
+                e->perturb = (id.qwords[0] ^ id.qwords[1]) % USEC_PER_MINUTE;
+        else
+                e->perturb = 0; /* This is a super early process without /proc and /etc ?? */
 }
 
 static int event_setup_timer_fd(
-- 
2.33.0

