kernel/linux.git/include/linux/tracepoint.h, branch v6.19.11

tracepoint: Do not warn for unused event that is exported

2025-10-24T20:43:14+00:00

There are a few generic events that may only be used by modules. They are defined and then set with EXPORT_TRACEPOINT*(). Mark events that are exported as being used, even though they still waste memory in the kernel proper. Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Cc: Arnd Bergmann Cc: Masahiro Yamada Cc: Nathan Chancellor Cc: Nicolas Schier Cc: Nick Desaulniers Cc: Catalin Marinas Cc: Linus Torvalds Cc: Randy Dunlap Cc: Stephen Rothwell Link: https://lore.kernel.org/20251022004453.089254920@kernel.org Signed-off-by: Steven Rostedt (Google)

tracing: Add a tracepoint verification check at build time

2025-10-24T20:43:14+00:00

If a tracepoint is defined via DECLARE_TRACE() or TRACE_EVENT() but never called (via the trace_() function), its metadata is still around in memory and not discarded. When created via TRACE_EVENT() the situation is worse because the TRACE_EVENT() creates metadata that can be around 5k per trace event. Having unused trace events causes several thousand of wasted bytes. Add a verifier that injects a string of the name of the tracepoint it calls that is added to the discarded section "__tracepoint_check". For every builtin tracepoint, its name (which is saved in the in-memory section "__tracepoint_strings") will have its name also in the "__tracepoint_check" section if it is used. Add a new program that is run on build called tracepoint-update. This is executed on the vmlinux.o before the __tracepoint_check section is discarded (the section is discarded before vmlinux is created). This program will create an array of each string in the __tracepoint_check section and then sort it. Then it will walk the strings in the __tracepoint_strings section and do a binary search to check if its name is in the __tracepoint_check section. If it is not, then it is unused and a warning is printed. Note, this currently only handles tracepoints that are builtin and not in modules. Enabling this currently with a given config produces: warning: tracepoint 'sched_move_numa' is unused. warning: tracepoint 'sched_stick_numa' is unused. warning: tracepoint 'sched_swap_numa' is unused. warning: tracepoint 'pelt_hw_tp' is unused. warning: tracepoint 'pelt_irq_tp' is unused. warning: tracepoint 'rcu_preempt_task' is unused. warning: tracepoint 'rcu_unlock_preempted_task' is unused. warning: tracepoint 'xdp_bulk_tx' is unused. warning: tracepoint 'xdp_redirect_map' is unused. warning: tracepoint 'xdp_redirect_map_err' is unused. warning: tracepoint 'vma_mas_szero' is unused. warning: tracepoint 'vma_store' is unused. warning: tracepoint 'hugepage_set_pmd' is unused. warning: tracepoint 'hugepage_set_pud' is unused. warning: tracepoint 'hugepage_update_pmd' is unused. warning: tracepoint 'hugepage_update_pud' is unused. warning: tracepoint 'block_rq_remap' is unused. warning: tracepoint 'xhci_dbc_handle_event' is unused. warning: tracepoint 'xhci_dbc_handle_transfer' is unused. warning: tracepoint 'xhci_dbc_gadget_ep_queue' is unused. warning: tracepoint 'xhci_dbc_alloc_request' is unused. warning: tracepoint 'xhci_dbc_free_request' is unused. warning: tracepoint 'xhci_dbc_queue_request' is unused. warning: tracepoint 'xhci_dbc_giveback_request' is unused. warning: tracepoint 'tcp_ao_wrong_maclen' is unused. warning: tracepoint 'tcp_ao_mismatch' is unused. warning: tracepoint 'tcp_ao_key_not_found' is unused. warning: tracepoint 'tcp_ao_rnext_request' is unused. warning: tracepoint 'tcp_ao_synack_no_key' is unused. warning: tracepoint 'tcp_ao_snd_sne_update' is unused. warning: tracepoint 'tcp_ao_rcv_sne_update' is unused. Some of the above is totally unused but others are not used due to their "trace_" functions being inside configs, in which case, the defined tracepoints should also be inside those same configs. Others are architecture specific but defined in generic code, where they should either be moved to the architecture or be surrounded by #ifdef for the architectures they are for. This tool could be updated to process modules in the future. I'd like to thank Mathieu Desnoyers for suggesting using strings instead of pointers, as using pointers in vmlinux.o required handling relocations and it required implementing almost a full feature linker to do so. To enable this check, run the build with: make UT=1 Note, when all the existing unused tracepoints are removed from the build, the "UT=1" will be removed and this will always be enabled when tracepoints are configured to warn on any new tracepoints. The reason this isn't always enabled now is because it will introduce a lot of warnings for the current unused tracepoints, and all bisects would end at this commit for those warnings. Link: https://lore.kernel.org/all/20250528114549.4d8a5e03@gandalf.local.home/ Cc: Masami Hiramatsu Cc: Mark Rutland Cc: Mathieu Desnoyers Cc: Andrew Morton Cc: Arnd Bergmann Cc: Masahiro Yamada Cc: Nathan Chancellor Cc: Nicolas Schier Cc: Nick Desaulniers Cc: Catalin Marinas Cc: Linus Torvalds Cc: Randy Dunlap Cc: Stephen Rothwell Link: https://lore.kernel.org/20251022004452.920728129@kernel.org Suggested-by: Mathieu Desnoyers # for using strings instead of pointers Signed-off-by: Steven Rostedt (Google)

tracepoint: Have tracepoints created with DECLARE_TRACE() have _tp suffix

2025-05-14T15:19:32+00:00

Most tracepoints in the kernel are created with TRACE_EVENT(). The TRACE_EVENT() macro (and DECLARE_EVENT_CLASS() and DEFINE_EVENT() where in reality, TRACE_EVENT() is just a helper macro that calls those other two macros), will create not only a tracepoint (the function trace_() used in the kernel), it also exposes the tracepoint to user space along with defining what fields will be saved by that tracepoint. There are a few places that tracepoints are created in the kernel that are not exposed to userspace via tracefs. They can only be accessed from code within the kernel. These tracepoints are created with DEFINE_TRACE() Most of these tracepoints end with "_tp". This is useful as when the developer sees that, they know that the tracepoint is for in-kernel only (meaning it can only be accessed inside the kernel, either directly by the kernel or indirectly via modules and BPF programs) and is not exposed to user space. Instead of making this only a process to add "_tp", enforce it by making the DECLARE_TRACE() append the "_tp" suffix to the tracepoint. This requires adding DECLARE_TRACE_EVENT() macros for the TRACE_EVENT() macro to use that keeps the original name. Link: https://lore.kernel.org/all/20250418083351.20a60e64@gandalf.local.home/ Cc: netdev Cc: Jiri Olsa Cc: Peter Zijlstra Cc: David Ahern Cc: Juri Lelli Cc: Breno Leitao Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Gabriele Monaco Cc: Masami Hiramatsu Link: https://lore.kernel.org/20250510163730.092fad5b@gandalf.local.home Acked-by: Mathieu Desnoyers Acked-by: Andrii Nakryiko Signed-off-by: Steven Rostedt (Google)

tracepoint: Reduce duplication of __DO_TRACE_CALL

2024-12-26T15:38:37+00:00

The logic for invoking __DO_TRACE_CALL was extracted to a static inline function called __rust_do_trace_##name so that Rust can call it directly. This logic does not include the static branch, to avoid a function call when the tracepoint is disabled. Since the C code needs to perform the same logic after checking the static key, this logic is currently duplicated. Thus, remove this duplication by having C call the static inline function too. Cc: Masami Hiramatsu Cc: Mathieu Desnoyers Link: https://lore.kernel.org/20241212131237.1988409-1-aliceryhl@google.com Signed-off-by: Alice Ryhl Signed-off-by: Steven Rostedt (Google)

Merge tag 'trace-v6.13-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2024-11-28T19:46:13+00:00

Pull more tracing updates from Steven Rostedt: - Add trace flag for NEED_RESCHED_LAZY Now that NEED_RESCHED_LAZY is upstream, add it to the status bits of the common_flags. This will now show when the NEED_RESCHED_LAZY flag is set that is used for debugging latency issues in the kernel via a trace. - Remove leftover "__idx" variable when SRCU was removed from the tracepoint code - Add rcu_tasks_trace guard To add a guard() around the tracepoint code, a rcu_tasks_trace guard needs to be created first. - Remove __DO_TRACE() macro and just call __DO_TRACE_CALL() directly The DO_TRACE() macro has conditional locking depending on what was passed into the macro parameters. As the guts of the macro has been moved to __DO_TRACE_CALL() to handle static call logic, there's no reason to keep the __DO_TRACE() macro around. It is better to just do the locking in place without the conditionals and call __DO_TRACE_CALL() from those locations. The "cond" passed in can also be moved out of that macro. This simplifies the code. - Remove the "cond" from the system call tracepoint macros The "cond" variable was added to allow some tracepoints to check a condition within the static_branch (jump/nop) logic. The system calls do not need this. Removing it simplifies the code. - Replace scoped_guard() with just guard() in the tracepoint logic guard() works just as well as scoped_guard() in the tracepoint logic and the scoped_guard() causes some issues. * tag 'trace-v6.13-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: tracing: Use guard() rather than scoped_guard() tracing: Remove cond argument from __DECLARE_TRACE_SYSCALL tracing: Remove conditional locking from __DO_TRACE() rcupdate_trace: Define rcu_tasks_trace lock guard tracing: Remove __idx variable from __DO_TRACE tracing: Move it_func[0] comment to the relevant context tracing: Record task flag NEED_RESCHED_LAZY.

tracing: Use guard() rather than scoped_guard()

2024-11-26T01:16:56+00:00

Using scoped_guard() in the implementation of trace_##name() adds an unnecessary level of indentation. Cc: Steven Rostedt Cc: Linus Torvalds Cc: Thomas Gleixner Cc: Michael Jeanson Cc: Masami Hiramatsu Cc: Peter Zijlstra Cc: Alexei Starovoitov Cc: Yonghong Song Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Mark Rutland Cc: Alexander Shishkin Cc: Namhyung Kim Cc: Andrii Nakryiko Cc: bpf@vger.kernel.org Cc: Joel Fernandes Cc: Jordan Rife Link: https://lore.kernel.org/20241125142514.2897143-1-mathieu.desnoyers@efficios.com Signed-off-by: Mathieu Desnoyers Signed-off-by: Steven Rostedt (Google)

Merge tag 'trace-rust-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2024-11-25T23:44:29+00:00

Pull rust trace event support from Steven Rostedt: "Allow Rust code to have trace events Trace events is a popular way to debug what is happening inside the kernel or just to find out what is happening. Rust code is being added to the Linux kernel but it currently does not support the tracing infrastructure. Add support of trace events inside Rust code" * tag 'trace-rust-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: rust: jump_label: skip formatting generated file jump_label: rust: pass a mut ptr to `static_key_count` samples: rust: fix `rust_print` build making it a combined module rust: add arch_static_branch jump_label: adjust inline asm to be consistent rust: samples: add tracepoint to Rust sample rust: add tracepoint support rust: add static_branch_unlikely for static_key_false

tracing: Remove cond argument from __DECLARE_TRACE_SYSCALL

2024-11-23T22:50:53+00:00

Syscall tracepoints do not require a "cond" argument, because they are meant to be used only for sys_enter and sys_exit instrumentation, which don't require condition evaluation. Cc: Linus Torvalds Cc: Thomas Gleixner Cc: Michael Jeanson Cc: Masami Hiramatsu Cc: Peter Zijlstra Cc: Alexei Starovoitov Cc: Yonghong Song Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Mark Rutland Cc: Alexander Shishkin Cc: Namhyung Kim Cc: Andrii Nakryiko Cc: bpf@vger.kernel.org Cc: Joel Fernandes Cc: Jordan Rife Cc: linux-trace-kernel@vger.kernel.org Link: https://lore.kernel.org/20241123153031.2884933-6-mathieu.desnoyers@efficios.com Signed-off-by: Mathieu Desnoyers Signed-off-by: Steven Rostedt (Google)

tracing: Remove conditional locking from __DO_TRACE()

2024-11-23T22:49:23+00:00

Remove conditional locking by moving the __DO_TRACE() code into trace_##name(). When the faultable syscall tracepoints were implemented, __DO_TRACE() had a rcuidle argument which selected between SRCU and preempt disable. Therefore, the RCU tasks trace protection for faultable syscall tracepoints was introduced using the same pattern. At that point, it did not appear obvious that this feedback from Linus [1] applied here as well, because the __DO_TRACE() modification was extending a pre-existing pattern. Shortly before pulling the faultable syscall tracepoints modifications, Steven removed the rcuidle argument and SRCU protection scheme entirely from tracepoint.h: commit 48bcda684823 ("tracing: Remove definition of trace_*_rcuidle()") This required a rebase of the faultable syscall tracepoints series, which missed a perfect opportunity to integrate the prior recommendation from Linus. In response to the pull request, Linus pointed out [2] that he was not pleased by the implementation, expecting this to be fixed in a follow up patch series. Move __DO_TRACE() code into trace_##name() within each of __DECLARE_TRACE() and __DECLARE_TRACE_SYSCALL(). Use a scoped guard to guard the preempt disable notrace and RCU tasks trace critical sections. Link: https://lore.kernel.org/all/CAHk-=wggDLDeTKbhb5hh--x=-DQd69v41137M72m6NOTmbD-cw@mail.gmail.com/ [1] Link: https://lore.kernel.org/lkml/CAHk-=witPrLcu22dZ93VCyRQonS7+-dFYhQbna=KBa-TAhayMw@mail.gmail.com/ [2] Fixes: a363d27cdbc2 ("tracing: Allow system call tracepoints to handle page faults") Cc: Linus Torvalds Cc: Thomas Gleixner Cc: Michael Jeanson Cc: Masami Hiramatsu Cc: Peter Zijlstra Cc: Alexei Starovoitov Cc: Yonghong Song Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Mark Rutland Cc: Alexander Shishkin Cc: Namhyung Kim Cc: Andrii Nakryiko Cc: bpf@vger.kernel.org Cc: Joel Fernandes Cc: Jordan Rife Cc: linux-trace-kernel@vger.kernel.org Link: https://lore.kernel.org/20241123153031.2884933-5-mathieu.desnoyers@efficios.com Signed-off-by: Mathieu Desnoyers Signed-off-by: Steven Rostedt (Google)

tracing: Remove idx variable from DO_TRACE

2024-11-23T22:47:22+00:00

Since the removal of SRCU-protected tracepoints, the __idx variable in __DO_TRACE is unused. Remove this variable. Fixes: 48bcda684823 ("tracing: Remove definition of trace_*_rcuidle()") Cc: Linus Torvalds Cc: Thomas Gleixner Cc: Michael Jeanson Cc: Masami Hiramatsu Cc: Peter Zijlstra Cc: Alexei Starovoitov Cc: Yonghong Song Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Arnaldo Carvalho de Melo Cc: Mark Rutland Cc: Alexander Shishkin Cc: Namhyung Kim Cc: Andrii Nakryiko Cc: bpf@vger.kernel.org Cc: Joel Fernandes Cc: Jordan Rife Link: https://lore.kernel.org/20241123153031.2884933-3-mathieu.desnoyers@efficios.com Signed-off-by: Mathieu Desnoyers Signed-off-by: Steven Rostedt (Google)