* [PATCH] tracing: Do not register unsupported perf events
@ 2025-12-16 23:24 Steven Rostedt
2025-12-22 9:27 ` Jiri Olsa
2025-12-23 18:22 ` Namhyung Kim
0 siblings, 2 replies; 4+ messages in thread
From: Steven Rostedt @ 2025-12-16 23:24 UTC (permalink / raw)
To: LKML, Linux Trace Kernel
Cc: Masami Hiramatsu, Mathieu Desnoyers, Ian Rogers,
Arnaldo Carvalho de Melo, Jiri Olsa, Namhyung Kim
From: Steven Rostedt <rostedt@goodmis.org>
Synthetic events currently do not have a function to register perf events.
This leads to calling the tracepoint register functions with a NULL
function pointer which triggers:
------------[ cut here ]------------
WARNING: kernel/tracepoint.c:175 at tracepoint_add_func+0x357/0x370, CPU#2: perf/2272
Modules linked in: kvm_intel kvm irqbypass
CPU: 2 UID: 0 PID: 2272 Comm: perf Not tainted 6.18.0-ftest-11964-ge022764176fc-dirty #323 PREEMPTLAZY
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
RIP: 0010:tracepoint_add_func+0x357/0x370
Code: 28 9c e8 4c 0b f5 ff eb 0f 4c 89 f7 48 c7 c6 80 4d 28 9c e8 ab 89 f4 ff 31 c0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc <0f> 0b 49 c7 c6 ea ff ff ff e9 ee fe ff ff 0f 0b e9 f9 fe ff ff 0f
RSP: 0018:ffffabc0c44d3c40 EFLAGS: 00010246
RAX: 0000000000000001 RBX: ffff9380aa9e4060 RCX: 0000000000000000
RDX: 000000000000000a RSI: ffffffff9e1d4a98 RDI: ffff937fcf5fd6c8
RBP: 0000000000000001 R08: 0000000000000007 R09: ffff937fcf5fc780
R10: 0000000000000003 R11: ffffffff9c193910 R12: 000000000000000a
R13: ffffffff9e1e5888 R14: 0000000000000000 R15: ffffabc0c44d3c78
FS: 00007f6202f5f340(0000) GS:ffff93819f00f000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055d3162281a8 CR3: 0000000106a56003 CR4: 0000000000172ef0
Call Trace:
<TASK>
tracepoint_probe_register+0x5d/0x90
synth_event_reg+0x3c/0x60
perf_trace_event_init+0x204/0x340
perf_trace_init+0x85/0xd0
perf_tp_event_init+0x2e/0x50
perf_try_init_event+0x6f/0x230
? perf_event_alloc+0x4bb/0xdc0
perf_event_alloc+0x65a/0xdc0
__se_sys_perf_event_open+0x290/0x9f0
do_syscall_64+0x93/0x7b0
? entry_SYSCALL_64_after_hwframe+0x76/0x7e
? trace_hardirqs_off+0x53/0xc0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
Instead, have the code return -ENODEV, which doesn't warn and has perf
error out with:
# perf record -e synthetic:futex_wait
Error:
The sys_perf_event_open() syscall returned with 19 (No such device) for event (synthetic:futex_wait).
"dmesg | grep -i perf" may provide additional information.
Ideally perf should support synthetic events, but for now just fix the
warning. The support can come later.
Cc: stable@vger.kernel.org
Fixes: 4b147936fa509 ("tracing: Add support for 'synthetic' events")
Reported-by: Ian Rogers <irogers@google.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/trace_events.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index a5a93d243047..754b14ca87a7 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -710,6 +710,8 @@ int trace_event_reg(struct trace_event_call *call,
#ifdef CONFIG_PERF_EVENTS
case TRACE_REG_PERF_REGISTER:
+ if (!call->class->perf_probe)
+ return -ENODEV;
return tracepoint_probe_register(call->tp,
call->class->perf_probe,
call);
--
2.51.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] tracing: Do not register unsupported perf events
2025-12-16 23:24 [PATCH] tracing: Do not register unsupported perf events Steven Rostedt
@ 2025-12-22 9:27 ` Jiri Olsa
2025-12-23 18:22 ` Namhyung Kim
1 sibling, 0 replies; 4+ messages in thread
From: Jiri Olsa @ 2025-12-22 9:27 UTC (permalink / raw)
To: Steven Rostedt
Cc: LKML, Linux Trace Kernel, Masami Hiramatsu, Mathieu Desnoyers,
Ian Rogers, Arnaldo Carvalho de Melo, Namhyung Kim
On Tue, Dec 16, 2025 at 06:24:40PM -0500, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
>
> Synthetic events currently do not have a function to register perf events.
> This leads to calling the tracepoint register functions with a NULL
> function pointer which triggers:
>
> ------------[ cut here ]------------
> WARNING: kernel/tracepoint.c:175 at tracepoint_add_func+0x357/0x370, CPU#2: perf/2272
> Modules linked in: kvm_intel kvm irqbypass
> CPU: 2 UID: 0 PID: 2272 Comm: perf Not tainted 6.18.0-ftest-11964-ge022764176fc-dirty #323 PREEMPTLAZY
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
> RIP: 0010:tracepoint_add_func+0x357/0x370
> Code: 28 9c e8 4c 0b f5 ff eb 0f 4c 89 f7 48 c7 c6 80 4d 28 9c e8 ab 89 f4 ff 31 c0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc <0f> 0b 49 c7 c6 ea ff ff ff e9 ee fe ff ff 0f 0b e9 f9 fe ff ff 0f
> RSP: 0018:ffffabc0c44d3c40 EFLAGS: 00010246
> RAX: 0000000000000001 RBX: ffff9380aa9e4060 RCX: 0000000000000000
> RDX: 000000000000000a RSI: ffffffff9e1d4a98 RDI: ffff937fcf5fd6c8
> RBP: 0000000000000001 R08: 0000000000000007 R09: ffff937fcf5fc780
> R10: 0000000000000003 R11: ffffffff9c193910 R12: 000000000000000a
> R13: ffffffff9e1e5888 R14: 0000000000000000 R15: ffffabc0c44d3c78
> FS: 00007f6202f5f340(0000) GS:ffff93819f00f000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055d3162281a8 CR3: 0000000106a56003 CR4: 0000000000172ef0
> Call Trace:
> <TASK>
> tracepoint_probe_register+0x5d/0x90
> synth_event_reg+0x3c/0x60
> perf_trace_event_init+0x204/0x340
> perf_trace_init+0x85/0xd0
> perf_tp_event_init+0x2e/0x50
> perf_try_init_event+0x6f/0x230
> ? perf_event_alloc+0x4bb/0xdc0
> perf_event_alloc+0x65a/0xdc0
> __se_sys_perf_event_open+0x290/0x9f0
> do_syscall_64+0x93/0x7b0
> ? entry_SYSCALL_64_after_hwframe+0x76/0x7e
> ? trace_hardirqs_off+0x53/0xc0
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
> Instead, have the code return -ENODEV, which doesn't warn and has perf
> error out with:
>
> # perf record -e synthetic:futex_wait
> Error:
> The sys_perf_event_open() syscall returned with 19 (No such device) for event (synthetic:futex_wait).
> "dmesg | grep -i perf" may provide additional information.
>
> Ideally perf should support synthetic events, but for now just fix the
> warning. The support can come later.
>
> Cc: stable@vger.kernel.org
> Fixes: 4b147936fa509 ("tracing: Add support for 'synthetic' events")
> Reported-by: Ian Rogers <irogers@google.com>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
lgtm
Acked-by: Jiri Olsa <jolsa@kernel.org>
jirka
> ---
> kernel/trace/trace_events.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index a5a93d243047..754b14ca87a7 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -710,6 +710,8 @@ int trace_event_reg(struct trace_event_call *call,
>
> #ifdef CONFIG_PERF_EVENTS
> case TRACE_REG_PERF_REGISTER:
> + if (!call->class->perf_probe)
> + return -ENODEV;
> return tracepoint_probe_register(call->tp,
> call->class->perf_probe,
> call);
> --
> 2.51.0
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] tracing: Do not register unsupported perf events
2025-12-16 23:24 [PATCH] tracing: Do not register unsupported perf events Steven Rostedt
2025-12-22 9:27 ` Jiri Olsa
@ 2025-12-23 18:22 ` Namhyung Kim
2025-12-23 21:46 ` Steven Rostedt
1 sibling, 1 reply; 4+ messages in thread
From: Namhyung Kim @ 2025-12-23 18:22 UTC (permalink / raw)
To: Steven Rostedt
Cc: LKML, Linux Trace Kernel, Masami Hiramatsu, Mathieu Desnoyers,
Ian Rogers, Arnaldo Carvalho de Melo, Jiri Olsa
Hi Steve,
On Tue, Dec 16, 2025 at 06:24:40PM -0500, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
>
> Synthetic events currently do not have a function to register perf events.
> This leads to calling the tracepoint register functions with a NULL
> function pointer which triggers:
>
> ------------[ cut here ]------------
> WARNING: kernel/tracepoint.c:175 at tracepoint_add_func+0x357/0x370, CPU#2: perf/2272
> Modules linked in: kvm_intel kvm irqbypass
> CPU: 2 UID: 0 PID: 2272 Comm: perf Not tainted 6.18.0-ftest-11964-ge022764176fc-dirty #323 PREEMPTLAZY
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
> RIP: 0010:tracepoint_add_func+0x357/0x370
> Code: 28 9c e8 4c 0b f5 ff eb 0f 4c 89 f7 48 c7 c6 80 4d 28 9c e8 ab 89 f4 ff 31 c0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc <0f> 0b 49 c7 c6 ea ff ff ff e9 ee fe ff ff 0f 0b e9 f9 fe ff ff 0f
> RSP: 0018:ffffabc0c44d3c40 EFLAGS: 00010246
> RAX: 0000000000000001 RBX: ffff9380aa9e4060 RCX: 0000000000000000
> RDX: 000000000000000a RSI: ffffffff9e1d4a98 RDI: ffff937fcf5fd6c8
> RBP: 0000000000000001 R08: 0000000000000007 R09: ffff937fcf5fc780
> R10: 0000000000000003 R11: ffffffff9c193910 R12: 000000000000000a
> R13: ffffffff9e1e5888 R14: 0000000000000000 R15: ffffabc0c44d3c78
> FS: 00007f6202f5f340(0000) GS:ffff93819f00f000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055d3162281a8 CR3: 0000000106a56003 CR4: 0000000000172ef0
> Call Trace:
> <TASK>
> tracepoint_probe_register+0x5d/0x90
> synth_event_reg+0x3c/0x60
> perf_trace_event_init+0x204/0x340
> perf_trace_init+0x85/0xd0
> perf_tp_event_init+0x2e/0x50
> perf_try_init_event+0x6f/0x230
> ? perf_event_alloc+0x4bb/0xdc0
> perf_event_alloc+0x65a/0xdc0
> __se_sys_perf_event_open+0x290/0x9f0
> do_syscall_64+0x93/0x7b0
> ? entry_SYSCALL_64_after_hwframe+0x76/0x7e
> ? trace_hardirqs_off+0x53/0xc0
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
> Instead, have the code return -ENODEV, which doesn't warn and has perf
> error out with:
>
> # perf record -e synthetic:futex_wait
> Error:
> The sys_perf_event_open() syscall returned with 19 (No such device) for event (synthetic:futex_wait).
> "dmesg | grep -i perf" may provide additional information.
>
> Ideally perf should support synthetic events, but for now just fix the
> warning. The support can come later.
>
> Cc: stable@vger.kernel.org
> Fixes: 4b147936fa509 ("tracing: Add support for 'synthetic' events")
> Reported-by: Ian Rogers <irogers@google.com>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Thanks,
Namhyung
> ---
> kernel/trace/trace_events.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index a5a93d243047..754b14ca87a7 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -710,6 +710,8 @@ int trace_event_reg(struct trace_event_call *call,
>
> #ifdef CONFIG_PERF_EVENTS
> case TRACE_REG_PERF_REGISTER:
> + if (!call->class->perf_probe)
> + return -ENODEV;
> return tracepoint_probe_register(call->tp,
> call->class->perf_probe,
> call);
> --
> 2.51.0
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] tracing: Do not register unsupported perf events
2025-12-23 18:22 ` Namhyung Kim
@ 2025-12-23 21:46 ` Steven Rostedt
0 siblings, 0 replies; 4+ messages in thread
From: Steven Rostedt @ 2025-12-23 21:46 UTC (permalink / raw)
To: Namhyung Kim
Cc: LKML, Linux Trace Kernel, Masami Hiramatsu, Mathieu Desnoyers,
Ian Rogers, Arnaldo Carvalho de Melo, Jiri Olsa
On Tue, 23 Dec 2025 10:22:18 -0800
Namhyung Kim <namhyung@kernel.org> wrote:
> Reviewed-by: Namhyung Kim <namhyung@kernel.org>
>
> Thanks,
> Namhyung
>
> > ---
> > kernel/trace/trace_events.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> > index a5a93d243047..754b14ca87a7 100644
> > --- a/kernel/trace/trace_events.c
> > +++ b/kernel/trace/trace_events.c
> > @@ -710,6 +710,8 @@ int trace_event_reg(struct trace_event_call *call,
> >
> > #ifdef CONFIG_PERF_EVENTS
> > case TRACE_REG_PERF_REGISTER:
> > + if (!call->class->perf_probe)
> > + return -ENODEV;
Thanks Namhyung (and Jiri), but this actually already made it upstream as
it was a bug fix and I wanted to get it into the next rc release (rc2).
But, the real fix is having perf be able to handle synthetic_events as real
events.
Can you please review this patch:
https://lore.kernel.org/linux-trace-kernel/20251217113920.50b56246@gandalf.local.home/
I plan on queuing that for the next merge window.
Thanks,
-- Steve
> > return tracepoint_probe_register(call->tp,
> > call->class->perf_probe,
> > call);
> > --
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2025-12-23 21:45 UTC | newest]
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2025-12-16 23:24 [PATCH] tracing: Do not register unsupported perf events Steven Rostedt
2025-12-22 9:27 ` Jiri Olsa
2025-12-23 18:22 ` Namhyung Kim
2025-12-23 21:46 ` Steven Rostedt
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