kernel/linux.git/include/linux/perf_event.h, branch v6.12.80

perf: Remove get_perf_callchain() init_nr argument

2025-12-18T12:54:49+00:00

[ Upstream commit e649bcda25b5ae1a30a182cc450f928a0b282c93 ] The 'init_nr' argument has double duty: it's used to initialize both the number of contexts and the number of stack entries. That's confusing and the callers always pass zero anyway. Hard code the zero. Signed-off-by: Josh Poimboeuf Signed-off-by: Steven Rostedt (Google) Signed-off-by: Peter Zijlstra (Intel) Acked-by: Namhyung Kim Acked-by: Alexei Starovoitov Link: https://lore.kernel.org/r/20250820180428.259565081@kernel.org Stable-dep-of: 23f852daa4ba ("bpf: Fix stackmap overflow check in __bpf_get_stackid()") Signed-off-by: Sasha Levin

perf: Avoid the read if the count is already updated

2025-05-29T09:03:02+00:00

[ Upstream commit 8ce939a0fa194939cc1f92dbd8bc1a7806e7d40a ] The event may have been updated in the PMU-specific implementation, e.g., Intel PEBS counters snapshotting. The common code should not read and overwrite the value. The PERF_SAMPLE_READ in the data->sample_type can be used to detect whether the PMU-specific value is available. If yes, avoid the pmu->read() in the common code. Add a new flag, skip_read, to track the case. Factor out a perf_pmu_read() to clean up the code. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Kan Liang Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20250121152303.3128733-3-kan.liang@linux.intel.com Signed-off-by: Sasha Levin

perf: Fix hang while freeing sigtrap event

2025-04-20T08:15:10+00:00

[ Upstream commit 56799bc035658738f362acec3e7647bb84e68933 ] Perf can hang while freeing a sigtrap event if a related deferred signal hadn't managed to be sent before the file got closed: perf_event_overflow() task_work_add(perf_pending_task) fput() task_work_add(____fput()) task_work_run() ____fput() perf_release() perf_event_release_kernel() _free_event() perf_pending_task_sync() task_work_cancel() -> FAILED rcuwait_wait_event() Once task_work_run() is running, the list of pending callbacks is removed from the task_struct and from this point on task_work_cancel() can't remove any pending and not yet started work items, hence the task_work_cancel() failure and the hang on rcuwait_wait_event(). Task work could be changed to remove one work at a time, so a work running on the current task can always cancel a pending one, however the wait / wake design is still subject to inverted dependencies when remote targets are involved, as pictured by Oleg: T1 T2 fd = perf_event_open(pid => T2->pid); fd = perf_event_open(pid => T1->pid); close(fd) close(fd) perf_event_overflow() perf_event_overflow() task_work_add(perf_pending_task) task_work_add(perf_pending_task) fput() fput() task_work_add(____fput()) task_work_add(____fput()) task_work_run() task_work_run() ____fput() ____fput() perf_release() perf_release() perf_event_release_kernel() perf_event_release_kernel() _free_event() _free_event() perf_pending_task_sync() perf_pending_task_sync() rcuwait_wait_event() rcuwait_wait_event() Therefore the only option left is to acquire the event reference count upon queueing the perf task work and release it from the task work, just like it was done before 3a5465418f5f ("perf: Fix event leak upon exec and file release") but without the leaks it fixed. Some adjustments are necessary to make it work: * A child event might dereference its parent upon freeing. Care must be taken to release the parent last. * Some places assuming the event doesn't have any reference held and therefore can be freed right away must instead put the reference and let the reference counting to its job. Reported-by: "Yi Lai" Closes: https://lore.kernel.org/all/Zx9Losv4YcJowaP%2F@ly-workstation/ Reported-by: syzbot+3c4321e10eea460eb606@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/673adf75.050a0220.87769.0024.GAE@google.com/ Fixes: 3a5465418f5f ("perf: Fix event leak upon exec and file release") Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20250304135446.18905-1-frederic@kernel.org Signed-off-by: Sasha Levin

perf/core: Simplify the perf_event_alloc() error path

2025-04-20T08:15:10+00:00

[ Upstream commit c70ca298036c58a88686ff388d3d367e9d21acf0 ] The error cleanup sequence in perf_event_alloc() is a subset of the existing _free_event() function (it must of course be). Split this out into __free_event() and simplify the error path. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Ravi Bangoria Link: https://lore.kernel.org/r/20241104135517.967889521@infradead.org Stable-dep-of: 56799bc03565 ("perf: Fix hang while freeing sigtrap event") Signed-off-by: Sasha Levin

perf/core: Add aux_pause, aux_resume, aux_start_paused

2025-04-20T08:15:10+00:00

[ Upstream commit 18d92bb57c39504d9da11c6ef604f58eb1d5a117 ] Hardware traces, such as instruction traces, can produce a vast amount of trace data, so being able to reduce tracing to more specific circumstances can be useful. The ability to pause or resume tracing when another event happens, can do that. Add ability for an event to "pause" or "resume" AUX area tracing. Add aux_pause bit to perf_event_attr to indicate that, if the event happens, the associated AUX area tracing should be paused. Ditto aux_resume. Do not allow aux_pause and aux_resume to be set together. Add aux_start_paused bit to perf_event_attr to indicate to an AUX area event that it should start in a "paused" state. Add aux_paused to struct hw_perf_event for AUX area events to keep track of the "paused" state. aux_paused is initialized to aux_start_paused. Add PERF_EF_PAUSE and PERF_EF_RESUME modes for ->stop() and ->start() callbacks. Call as needed, during __perf_event_output(). Add aux_in_pause_resume to struct perf_buffer to prevent races with the NMI handler. Pause/resume in NMI context will miss out if it coincides with another pause/resume. To use aux_pause or aux_resume, an event must be in a group with the AUX area event as the group leader. Example (requires Intel PT and tools patches also): $ perf record --kcore -e intel_pt/aux-action=start-paused/k,syscalls:sys_enter_newuname/aux-action=resume/,syscalls:sys_exit_newuname/aux-action=pause/ uname Linux [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.043 MB perf.data ] $ perf script --call-trace uname 30805 [000] 24001.058782799: name: 0x7ffc9c1865b0 uname 30805 [000] 24001.058784424: psb offs: 0 uname 30805 [000] 24001.058784424: cbr: 39 freq: 3904 MHz (139%) uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) debug_smp_processor_id uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) __x64_sys_newuname uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) down_read uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) __cond_resched uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) preempt_count_add uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) in_lock_functions uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) preempt_count_sub uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) up_read uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) preempt_count_add uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) in_lock_functions uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) preempt_count_sub uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) _copy_to_user uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) syscall_exit_to_user_mode uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) syscall_exit_work uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) perf_syscall_exit uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) debug_smp_processor_id uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_trace_buf_alloc uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_swevent_get_recursion_context uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) debug_smp_processor_id uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) debug_smp_processor_id uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_tp_event uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_trace_buf_update uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) tracing_gen_ctx_irq_test uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_swevent_event uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __perf_event_account_interrupt uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __this_cpu_preempt_check uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_event_output_forward uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_event_aux_pause uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) ring_buffer_get uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __rcu_read_lock uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __rcu_read_unlock uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) pt_event_stop uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) debug_smp_processor_id uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) debug_smp_processor_id uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) native_write_msr uname 30805 [000] 24001.058785463: ([kernel.kallsyms]) native_write_msr uname 30805 [000] 24001.058785639: 0x0 Signed-off-by: Adrian Hunter Signed-off-by: Peter Zijlstra (Intel) Acked-by: James Clark Link: https://lkml.kernel.org/r/20241022155920.17511-3-adrian.hunter@intel.com Stable-dep-of: 56799bc03565 ("perf: Fix hang while freeing sigtrap event") Signed-off-by: Sasha Levin

perf/core: Save raw sample data conditionally based on sample type

2025-02-08T08:56:53+00:00

[ Upstream commit b9c44b91476b67327a521568a854babecc4070ab ] Currently, space for raw sample data is always allocated within sample records for both BPF output and tracepoint events. This leads to unused space in sample records when raw sample data is not requested. This patch enforces checking sample type of an event in perf_sample_save_raw_data(). So raw sample data will only be saved if explicitly requested, reducing overhead when it is not needed. Fixes: 0a9081cf0a11 ("perf/core: Add perf_sample_save_raw_data() helper") Signed-off-by: Yabin Cui Signed-off-by: Ingo Molnar Reviewed-by: Ian Rogers Acked-by: Namhyung Kim Link: https://lore.kernel.org/r/20240515193610.2350456-2-yabinc@google.com Signed-off-by: Sasha Levin

Merge tag 'perf-core-2024-09-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2024-09-18T13:03:58+00:00

Pull perf events updates from Ingo Molnar: - Implement per-PMU context rescheduling to significantly improve single-PMU performance, and related cleanups/fixes (Peter Zijlstra and Namhyung Kim) - Fix ancient bug resulting in a lot of events being dropped erroneously at higher sampling frequencies (Luo Gengkun) - uprobes enhancements: - Implement RCU-protected hot path optimizations for better performance: "For baseline vs SRCU, peak througput increased from 3.7 M/s (million uprobe triggerings per second) up to about 8 M/s. For uretprobes it's a bit more modest with bump from 2.4 M/s to 5 M/s. For SRCU vs RCU Tasks Trace, peak throughput for uprobes increases further from 8 M/s to 10.3 M/s (+28%!), and for uretprobes from 5.3 M/s to 5.8 M/s (+11%), as we have more work to do on uretprobes side. Even single-thread (no contention) performance is slightly better: 3.276 M/s to 3.396 M/s (+3.5%) for uprobes, and 2.055 M/s to 2.174 M/s (+5.8%) for uretprobes." (Andrii Nakryiko et al) - Document mmap_lock, don't abuse get_user_pages_remote() (Oleg Nesterov) - Cleanups & fixes to prepare for future work: - Remove uprobe_register_refctr() - Simplify error handling for alloc_uprobe() - Make uprobe_register() return struct uprobe * - Fold __uprobe_unregister() into uprobe_unregister() - Shift put_uprobe() from delete_uprobe() to uprobe_unregister() - BPF: Fix use-after-free in bpf_uprobe_multi_link_attach() (Oleg Nesterov) - New feature & ABI extension: allow events to use PERF_SAMPLE READ with inheritance, enabling sample based profiling of a group of counters over a hierarchy of processes or threads (Ben Gainey) - Intel uncore & power events updates: - Add Arrow Lake and Lunar Lake support - Add PERF_EV_CAP_READ_SCOPE - Clean up and enhance cpumask and hotplug support (Kan Liang) - Add LNL uncore iMC freerunning support - Use D0:F0 as a default device (Zhenyu Wang) - Intel PT: fix AUX snapshot handling race (Adrian Hunter) - Misc fixes and cleanups (James Clark, Jiri Olsa, Oleg Nesterov and Peter Zijlstra) * tag 'perf-core-2024-09-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (40 commits) dmaengine: idxd: Clean up cpumask and hotplug for perfmon iommu/vt-d: Clean up cpumask and hotplug for perfmon perf/x86/intel/cstate: Clean up cpumask and hotplug perf: Add PERF_EV_CAP_READ_SCOPE perf: Generic hotplug support for a PMU with a scope uprobes: perform lockless SRCU-protected uprobes_tree lookup rbtree: provide rb_find_rcu() / rb_find_add_rcu() perf/uprobe: split uprobe_unregister() uprobes: travers uprobe's consumer list locklessly under SRCU protection uprobes: get rid of enum uprobe_filter_ctx in uprobe filter callbacks uprobes: protected uprobe lifetime with SRCU uprobes: revamp uprobe refcounting and lifetime management bpf: Fix use-after-free in bpf_uprobe_multi_link_attach() perf/core: Fix small negative period being ignored perf: Really fix event_function_call() locking perf: Optimize __pmu_ctx_sched_out() perf: Add context time freeze perf: Fix event_function_call() locking perf: Extract a few helpers perf: Optimize context reschedule for single PMU cases ...

perf: Add PERF_EV_CAP_READ_SCOPE

2024-09-10T09:44:13+00:00

Usually, an event can be read from any CPU of the scope. It doesn't need to be read from the advertised CPU. Add a new event cap, PERF_EV_CAP_READ_SCOPE. An event of a PMU with scope can be read from any active CPU in the scope. Signed-off-by: Kan Liang Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20240802151643.1691631-3-kan.liang@linux.intel.com

perf: Generic hotplug support for a PMU with a scope

2024-09-10T09:44:12+00:00

The perf subsystem assumes that the counters of a PMU are per-CPU. So the user space tool reads a counter from each CPU in the system wide mode. However, many PMUs don't have a per-CPU counter. The counter is effective for a scope, e.g., a die or a socket. To address this, a cpumask is exposed by the kernel driver to restrict to one CPU to stand for a specific scope. In case the given CPU is removed, the hotplug support has to be implemented for each such driver. The codes to support the cpumask and hotplug are very similar. - Expose a cpumask into sysfs - Pickup another CPU in the same scope if the given CPU is removed. - Invoke the perf_pmu_migrate_context() to migrate to a new CPU. - In event init, always set the CPU in the cpumask to event->cpu Similar duplicated codes are implemented for each such PMU driver. It would be good to introduce a generic infrastructure to avoid such duplication. 5 popular scopes are implemented here, core, die, cluster, pkg, and the system-wide. The scope can be set when a PMU is registered. If so, a "cpumask" is automatically exposed for the PMU. The "cpumask" is from the perf_online__mask, which is to track the active CPU for each scope. They are set when the first CPU of the scope is online via the generic perf hotplug support. When a corresponding CPU is removed, the perf_online__mask is updated accordingly and the PMU will be moved to a new CPU from the same scope if possible. Signed-off-by: Kan Liang Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20240802151643.1691631-2-kan.liang@linux.intel.com

drivers/perf: arm_spe: Use perf_allow_kernel() for permissions

2024-08-30T10:42:24+00:00

Use perf_allow_kernel() for 'pa_enable' (physical addresses), 'pct_enable' (physical timestamps) and context IDs. This means that perf_event_paranoid is now taken into account and LSM hooks can be used, which is more consistent with other perf_event_open calls. For example PERF_SAMPLE_PHYS_ADDR uses perf_allow_kernel() rather than just perfmon_capable(). This also indirectly fixes the following error message which is misleading because perf_event_paranoid is not taken into account by perfmon_capable(): $ perf record -e arm_spe/pa_enable/ Error: Access to performance monitoring and observability operations is limited. Consider adjusting /proc/sys/kernel/perf_event_paranoid setting ... Suggested-by: Al Grant Signed-off-by: James Clark Link: https://lore.kernel.org/r/20240827145113.1224604-1-james.clark@linaro.org Link: https://lore.kernel.org/all/20240807120039.GD37996@noisy.programming.kicks-ass.net/ Signed-off-by: Will Deacon