From: Bruce Ashfield <bruce.ashfi...@gmail.com>
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 <dely...@fb.com>
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 <dely...@fb.com>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Acked-by: Steven Rostedt (Google) <rost...@goodmis.org>
Link:
https://lkml.kernel.org/r/c8a6930dfdd58a4a5755fc01732675472979732b.ca...@fb.com
By reordering the parameters (again) we can get back up and building.
Signed-off-by: Bruce Ashfield <bruce.ashfi...@gmail.com>
---
Hi all,
This is more than likely NOT a correct fix, but while working on the
yocto -dev reference kernel, I ran into this build failure against
5.18-rc7.
I didn't see any sign of another fix on the mailing list, so I wanted
to send this in case anyone else runs into the failure and to check
to see if there's a better fix in progress.
Cheers,
Bruce
include/instrumentation/events/sched.h | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/include/instrumentation/events/sched.h
b/include/instrumentation/events/sched.h
index 339bec9..f9e9c38 100644
--- a/include/instrumentation/events/sched.h
+++ b/include/instrumentation/events/sched.h
@@ -23,8 +23,9 @@
#if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,18,0))
static inline long __trace_sched_switch_state(bool preempt,
- unsigned int prev_state,
- struct task_struct *p)
+ struct task_struct *p,
+ struct task_struct *n,
+ unsigned int prev_state )
{
unsigned int state;
@@ -356,20 +357,20 @@ 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)
ctf_integer(pid_t, prev_tid, prev->pid)
ctf_integer(int, prev_prio, prev->prio - MAX_RT_PRIO)
#ifdef CONFIG_LTTNG_EXPERIMENTAL_BITWISE_ENUM
- ctf_enum(task_state, long, prev_state,
__trace_sched_switch_state(preempt, prev_state, prev))
+ ctf_enum(task_state, long, prev_state,
__trace_sched_switch_state(preempt, prev, next, prev_state))
#else
- ctf_integer(long, prev_state,
__trace_sched_switch_state(preempt, prev_state, prev))
+ ctf_integer(long, prev_state,
__trace_sched_switch_state(preempt, prev, next, prev_state))
#endif
ctf_array_text(char, next_comm, next->comm, TASK_COMM_LEN)
ctf_integer(pid_t, next_tid, next->pid)
--
2.19.1
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