From: Bruce Ashfield <bruce.ashfield@...>

lttng-modules fails to build against 5.18-rc7, the details of the fix
are as follows:

The commit [fix: sched/tracing: Don't re-read p->state when emitting
sched_switch event (v5.18)] was correct, but the kernel changed their
mind with the following commit:

commit 9c2136be0878c88c53dea26943ce40bb03ad8d8d
Author: Delyan Kratunov <delyank@...>
Date: Wed May 11 18:28:36 2022 +0000

sched/tracing: Append prev_state to tp args instead

Commit fa2c3254d7cf (sched/tracing: Don't re-read p->state when emitting
sched_switch event, 2022-01-20) added a new prev_state argument to the
sched_switch tracepoint, before the prev task_struct pointer.

This reordering of arguments broke BPF programs that use the raw
tracepoint (e.g. tp_btf programs). The type of the second argument has
changed and existing programs that assume a task_struct* argument
(e.g. for bpf_task_storage access) will now fail to verify.

If we instead append the new argument to the end, all existing programs
would continue to work and can conditionally extract the prev_state
argument on supported kernel versions.

Fixes: fa2c3254d7cf (sched/tracing: Don't re-read p->state when emitting sched_switch event, 2022-01-20)
Signed-off-by: Delyan Kratunov <delyank@...>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...>
Acked-by: Steven Rostedt (Google) <rostedt@...>
Link: https://lkml.kernel.org/r/c8a6930dfdd58a4a5755fc01732675472979732b.camel@fb.com

By reordering the parameters (again) we can get back up and building.

Upstream-Status: Backport

Signed-off-by: Bruce Ashfield <bruce.ashfield@...>
---

v2: upstream merged their fix for 5.18-rc7+, so I've updated with that
fix and spun v2.

Bruce


...g-Append-prev_state-to-tp-args-inste.patch | 59 +++++++++++++++++++
.../lttng/lttng-modules_2.13.3.bb | 1 +
2 files changed, 60 insertions(+)
create mode 100644 meta/recipes-kernel/lttng/lttng-modules/0001-fix-sched-tracing-Append-prev_state-to-tp-args-inste.patch

diff --git a/meta/recipes-kernel/lttng/lttng-modules/0001-fix-sched-tracing-Append-prev_state-to-tp-args-inste.patch b/meta/recipes-kernel/lttng/lttng-modules/0001-fix-sched-tracing-Append-prev_state-to-tp-args-inste.patch
new file mode 100644
index 0000000000..b41053b6bc
--- /dev/null
+++ b/meta/recipes-kernel/lttng/lttng-modules/0001-fix-sched-tracing-Append-prev_state-to-tp-args-inste.patch
@@ -0,0 +1,59 @@
+From 9c5b8de32b5745f3ff31079c02da64595e101bee Mon Sep 17 00:00:00 2001
+From: Michael Jeanson <mjeanson@...>
+Date: Tue, 17 May 2022 11:46:29 -0400
+Subject: [PATCH] fix: sched/tracing: Append prev_state to tp args instead
+ (v5.18)
+
+See upstream commit :
+
+ commit 9c2136be0878c88c53dea26943ce40bb03ad8d8d
+ Author: Delyan Kratunov <delyank@...>
+ Date: Wed May 11 18:28:36 2022 +0000
+
+ sched/tracing: Append prev_state to tp args instead
+
+ Commit fa2c3254d7cf (sched/tracing: Don't re-read p->state when emitting
+ sched_switch event, 2022-01-20) added a new prev_state argument to the
+ sched_switch tracepoint, before the prev task_struct pointer.
+
+ This reordering of arguments broke BPF programs that use the raw
+ tracepoint (e.g. tp_btf programs). The type of the second argument has
+ changed and existing programs that assume a task_struct* argument
+ (e.g. for bpf_task_storage access) will now fail to verify.
+
+ If we instead append the new argument to the end, all existing programs
+ would continue to work and can conditionally extract the prev_state
+ argument on supported kernel versions.
+
+
+Upstream-Status: Backport
+
+Change-Id: Ife2ec88a8bea2743562590cbd357068d7773863f
+Signed-off-by: Michael Jeanson <mjeanson@...>
+Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...>
+---
+ include/instrumentation/events/sched.h | 6 +++---
+ 1 file changed, 3 insertions(+), 3 deletions(-)
+
+diff --git a/include/instrumentation/events/sched.h b/include/instrumentation/events/sched.h
+index 339bec94..c1c3df15 100644
+--- a/include/instrumentation/events/sched.h
++++ b/include/instrumentation/events/sched.h
+@@ -356,11 +356,11 @@ LTTNG_TRACEPOINT_EVENT_INSTANCE(sched_wakeup_template, sched_wakeup_new,
+ LTTNG_TRACEPOINT_EVENT(sched_switch,
+
+ TP_PROTO(bool preempt,
+- unsigned int prev_state,
+ struct task_struct *prev,
+- struct task_struct *next),
++ struct task_struct *next,
++ unsigned int prev_state),
+
+- TP_ARGS(preempt, prev_state, prev, next),
++ TP_ARGS(preempt, prev, next, prev_state),
+
+ TP_FIELDS(
+ ctf_array_text(char, prev_comm, prev->comm, TASK_COMM_LEN)
+--
+2.19.1
+
diff --git a/meta/recipes-kernel/lttng/lttng-modules_2.13.3.bb b/meta/recipes-kernel/lttng/lttng-modules_2.13.3.bb
index 2b00534e53..a5e6b906d2 100644
--- a/meta/recipes-kernel/lttng/lttng-modules_2.13.3.bb
+++ b/meta/recipes-kernel/lttng/lttng-modules_2.13.3.bb
@@ -20,6 +20,7 @@ SRC_URI = "https://lttng.org/files/${BPN}/${BPN}-${PV}.tar.bz2 \
file://0008-fix-scsi-core-Remove-scsi-scsi_request.h-v5.18.patch \
file://0009-Rename-genhd-wrapper-to-blkdev.patch \
file://0010-fix-mm-compaction-cleanup-the-compaction-trace-event.patch \
+ file://0001-fix-sched-tracing-Append-prev_state-to-tp-args-inste.patch \
"

# Use :append here so that the patch is applied also when using devupstream
--
2.19.1