From 934b67ac0b31fe7a349cb73aeb45e54bd67c5a48 Mon Sep 17 00:00:00 2001
From: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>
Date: Fri, 5 Jul 2024 15:15:53 +0200
Subject: [PATCH] Trace sched events from stage1

Events from the kthread that dumps the buffer to the console are
filtered, otherwise we make an infinite loop.
---
 lagarto-ox.nix | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/lagarto-ox.nix b/lagarto-ox.nix
index 319cb5c..2da2c5e 100644
--- a/lagarto-ox.nix
+++ b/lagarto-ox.nix
@@ -87,6 +87,16 @@
       preDeviceCommands = ''
         echo "Creating a heartbeat counter at 0x1bfff0000"
         sh -c 'hb=0; while [ 1 ]; do let hb=$hb+1; devmem 0x1bfff0000 32 $hb; done' &
+      ''
+      +
+      # Exclude the second pid, which is the kthread that will dump the trace to
+      # the console, otherwise we live lock the kernel. Then enable the sched
+      # events.
+      ''
+        echo "Exclude pid 2 from sched"
+        echo '(prev_pid != 2 && next_pid != 2)' > /sys/kernel/debug/tracing/events/sched/filter
+        echo "Enable all events from sched subsystem"
+        echo 1 > /sys/kernel/debug/tracing/events/sched/enable
       '';
     };