* [lttng-dev] [PATCH] sched/tracing: fix __trace_sched_switch_state (5.18-rc7+)
@ 2022-05-19 15:02 Bruce Ashfield via lttng-dev
2022-05-19 15:31 ` Mathieu Desnoyers via lttng-dev
0 siblings, 1 reply; 3+ messages in thread
From: Bruce Ashfield via lttng-dev @ 2022-05-19 15:02 UTC (permalink / raw)
To: lttng-dev
From: Bruce Ashfield <bruce.ashfield@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 <delyank@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 <delyank@fb.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/c8a6930dfdd58a4a5755fc01732675472979732b.camel@fb.com
By reordering the parameters (again) we can get back up and building.
Signed-off-by: Bruce Ashfield <bruce.ashfield@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
_______________________________________________
lttng-dev mailing list
lttng-dev@lists.lttng.org
https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [lttng-dev] [PATCH] sched/tracing: fix __trace_sched_switch_state (5.18-rc7+)
2022-05-19 15:02 [lttng-dev] [PATCH] sched/tracing: fix __trace_sched_switch_state (5.18-rc7+) Bruce Ashfield via lttng-dev
@ 2022-05-19 15:31 ` Mathieu Desnoyers via lttng-dev
2022-05-19 16:01 ` Bruce Ashfield via lttng-dev
0 siblings, 1 reply; 3+ messages in thread
From: Mathieu Desnoyers via lttng-dev @ 2022-05-19 15:31 UTC (permalink / raw)
To: bruce ashfield; +Cc: lttng-dev
----- On May 19, 2022, at 11:02 AM, Bruce Ashfield via lttng-dev lttng-dev@lists.lttng.org wrote:
> From: Bruce Ashfield <bruce.ashfield@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 <delyank@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 <delyank@fb.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> Link:
> https://lkml.kernel.org/r/c8a6930dfdd58a4a5755fc01732675472979732b.camel@fb.com
>
> By reordering the parameters (again) we can get back up and building.
>
> Signed-off-by: Bruce Ashfield <bruce.ashfield@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.
Hi Bruce,
Please see: https://review.lttng.org/c/lttng-modules/+/8045
I was planning to merge it today, unless you have objections.
I notice that in your own patch, you modify the arguments passed to
__trace_sched_switch_state(), althrough I don't see them changing in
the upstream kernel. Am I missing something ?
Thanks,
Mathieu
>
> 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
>
> _______________________________________________
> lttng-dev mailing list
> lttng-dev@lists.lttng.org
> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
_______________________________________________
lttng-dev mailing list
lttng-dev@lists.lttng.org
https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [lttng-dev] [PATCH] sched/tracing: fix __trace_sched_switch_state (5.18-rc7+)
2022-05-19 15:31 ` Mathieu Desnoyers via lttng-dev
@ 2022-05-19 16:01 ` Bruce Ashfield via lttng-dev
0 siblings, 0 replies; 3+ messages in thread
From: Bruce Ashfield via lttng-dev @ 2022-05-19 16:01 UTC (permalink / raw)
To: Mathieu Desnoyers; +Cc: lttng-dev
On Thu, May 19, 2022 at 11:31 AM Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
>
>
> ----- On May 19, 2022, at 11:02 AM, Bruce Ashfield via lttng-dev lttng-dev@lists.lttng.org wrote:
>
> > From: Bruce Ashfield <bruce.ashfield@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 <delyank@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 <delyank@fb.com>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> > Link:
> > https://lkml.kernel.org/r/c8a6930dfdd58a4a5755fc01732675472979732b.camel@fb.com
> >
> > By reordering the parameters (again) we can get back up and building.
> >
> > Signed-off-by: Bruce Ashfield <bruce.ashfield@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.
>
> Hi Bruce,
>
> Please see: https://review.lttng.org/c/lttng-modules/+/8045
>
> I was planning to merge it today, unless you have objections.
>
> I notice that in your own patch, you modify the arguments passed to
> __trace_sched_switch_state(), althrough I don't see them changing in
> the upstream kernel. Am I missing something ?
No objects here. That is obviously better than mine :) I swear I saw
the order of the arguments changing when I looked at the kernel, and
had a secondary compile error in those calls .. but I very easily could
have been mistaken.
Bruce
>
> Thanks,
>
> Mathieu
>
> >
> > 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
> >
> > _______________________________________________
> > lttng-dev mailing list
> > lttng-dev@lists.lttng.org
> > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
--
- Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end
- "Use the force Harry" - Gandalf, Star Trek II
_______________________________________________
lttng-dev mailing list
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https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
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2022-05-19 15:02 [lttng-dev] [PATCH] sched/tracing: fix __trace_sched_switch_state (5.18-rc7+) Bruce Ashfield via lttng-dev
2022-05-19 15:31 ` Mathieu Desnoyers via lttng-dev
2022-05-19 16:01 ` Bruce Ashfield via lttng-dev
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