[ The biggest change since v6 is that it only works for task events. That is, if the event is per CPU it will still do the old unwinding.
perf record -g ... # does the deferred unwinding perf record -a -g ... # still does the old immediatel unwinding I have patches that solve the per CPU deferred unwinding that I'm currently cleaning up and will post shortly. ] I'm currently working on getting sframe support from the kernel. Josh Poimboeuf did a lot of the hard work already, but he told me he doesn't have time to continue it so I'm picking it up where he left off. His last series of v4 is here: https://lore.kernel.org/all/cover.1737511963.git.jpoim...@kernel.org/ It covers a lot of topics as he found issues with other aspects of the kernel that needed to be fixed for sframes to work properly. This series focuses only on implementing the deferred user space stack tracing that can be used by perf. It does not implement sframe support nor does it add an interface that can be used by ftrace or LTTng (that will come later). I based this off of the latest tip/master: 397310f19ee88e9af17ab24cb69dcbb49292c8cb Changes since v6: https://lore.kernel.org/linux-trace-kernel/20250425145422.132820...@goodmis.org/ - Use (current->flags & PF_KTHREAD) instead of !(current->mm) for testing if a task is a kernel thread or not. (Josh Poimboeuf) - Use (current->flags & PF_EXITING) instead of checking !current->mm - Only defer unwind if event is attached to a specific task (not global per CPU) - Added a missing rcuwait_init(&event->pending_unwind_wait); Josh Poimboeuf (12): unwind_user: Add user space unwinding API unwind_user: Add frame pointer support unwind_user/x86: Enable frame pointer unwinding on x86 perf/x86: Rename and move get_segment_base() and make it global unwind_user: Add compat mode frame pointer support unwind_user/x86: Enable compat mode frame pointer unwinding on x86 unwind_user/deferred: Add unwind cache perf: Remove get_perf_callchain() init_nr argument perf: Have get_perf_callchain() return NULL if crosstask and user are set perf: Simplify get_perf_callchain() user logic perf: Skip user unwind if the task is a kernel thread. perf: Support deferred user callchains Namhyung Kim (4): perf tools: Minimal CALLCHAIN_DEFERRED support perf record: Enable defer_callchain for user callchains perf script: Display PERF_RECORD_CALLCHAIN_DEFERRED perf tools: Merge deferred user callchains Steven Rostedt (2): unwind_user/deferred: Add unwind_deferred_trace() perf: Use current->flags & PF_KTHREAD instead of current->mm == NULL ---- MAINTAINERS | 8 ++ arch/Kconfig | 14 +++ arch/x86/Kconfig | 2 + arch/x86/events/core.c | 44 +------- arch/x86/include/asm/ptrace.h | 2 + arch/x86/include/asm/unwind_user.h | 61 +++++++++++ arch/x86/include/asm/unwind_user_types.h | 17 +++ arch/x86/kernel/ptrace.c | 38 +++++++ include/asm-generic/Kbuild | 2 + include/asm-generic/unwind_user.h | 24 +++++ include/asm-generic/unwind_user_types.h | 9 ++ include/linux/entry-common.h | 2 + include/linux/perf_event.h | 9 +- include/linux/sched.h | 5 + include/linux/unwind_deferred.h | 31 ++++++ include/linux/unwind_deferred_types.h | 14 +++ include/linux/unwind_user.h | 15 +++ include/linux/unwind_user_types.h | 35 ++++++ include/uapi/linux/perf_event.h | 19 +++- kernel/Makefile | 1 + kernel/bpf/stackmap.c | 8 +- kernel/events/callchain.c | 47 ++++---- kernel/events/core.c | 173 +++++++++++++++++++++++++++++- kernel/fork.c | 4 + kernel/unwind/Makefile | 1 + kernel/unwind/deferred.c | 61 +++++++++++ kernel/unwind/user.c | 130 ++++++++++++++++++++++ tools/include/uapi/linux/perf_event.h | 19 +++- tools/lib/perf/include/perf/event.h | 7 ++ tools/perf/Documentation/perf-script.txt | 5 + tools/perf/builtin-script.c | 92 ++++++++++++++++ tools/perf/util/callchain.c | 24 +++++ tools/perf/util/callchain.h | 3 + tools/perf/util/event.c | 1 + tools/perf/util/evlist.c | 1 + tools/perf/util/evlist.h | 1 + tools/perf/util/evsel.c | 39 +++++++ tools/perf/util/evsel.h | 1 + tools/perf/util/machine.c | 1 + tools/perf/util/perf_event_attr_fprintf.c | 1 + tools/perf/util/sample.h | 3 +- tools/perf/util/session.c | 78 ++++++++++++++ tools/perf/util/tool.c | 2 + tools/perf/util/tool.h | 4 +- 44 files changed, 985 insertions(+), 73 deletions(-) create mode 100644 arch/x86/include/asm/unwind_user.h create mode 100644 arch/x86/include/asm/unwind_user_types.h create mode 100644 include/asm-generic/unwind_user.h create mode 100644 include/asm-generic/unwind_user_types.h create mode 100644 include/linux/unwind_deferred.h create mode 100644 include/linux/unwind_deferred_types.h create mode 100644 include/linux/unwind_user.h create mode 100644 include/linux/unwind_user_types.h create mode 100644 kernel/unwind/Makefile create mode 100644 kernel/unwind/deferred.c create mode 100644 kernel/unwind/user.c
