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linux/kernel/trace
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Steven Rostedt c4f1fe47b1 tracing: Better separate SNAPSHOT and MAX_TRACE options 
The latency tracers (scheduler, irqsoff, etc) were created when tracing
was first added. These tracers required a "snapshot" buffer that was the
same size as the ring buffer being written to. When a new max latency was
hit, the main ring buffer would swap with the snapshot buffer so that the
trace leading up to the latency would be saved in the snapshot buffer (The
snapshot buffer is never written to directly and the data within it can be
viewed without fear of being overwritten).

Later, a new feature was added to allow snapshots to be taken by user
space or even event triggers. This created a "snapshot" file that allowed
users to trigger a snapshot from user space to save the current trace.

The config for this new feature (CONFIG_TRACER_SNAPSHOT) would select the
latency tracer config (CONFIG_TRACER_MAX_LATENCY) as it would need all the
functionality from it as it already existed. But this was incorrect. As
the snapshot feature is really what the latency tracers need and not the
other way around.

Have CONFIG_TRACER_MAX_TRACE select CONFIG_TRACER_SNAPSHOT where the
tracers that needs the max latency buffer selects the TRACE_MAX_TRACE
which will then select TRACER_SNAPSHOT.

Also, go through trace.c and trace.h and make the code that only needs the
TRACER_MAX_TRACE protected by that and the code that always requires the
snapshot to be protected by TRACER_SNAPSHOT.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://patch.msgid.link/20260208183856.767870992@kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2026-02-08 21:01:13 -05:00
..
rv rv: Convert to use __free 2025-12-02 07:28:32 +01:00
blktrace.c blktrace: Make init_blk_tracer() asynchronous 2026-02-06 15:27:00 -05:00
bpf_trace.c bpf: Have __bpf_trace_run() use rcu_read_lock_dont_migrate() 2026-01-30 10:43:48 -05:00
bpf_trace.h tracing/treewide: Remove second parameter of __assign_str() 2024-05-22 20:14:47 -04:00
error_report-traces.c
fgraph.c tracing: Fix typo in fpgraph.c 2025-12-05 15:43:39 -05:00
fprobe.c tracing fixes for v6.19: 2025-12-06 13:49:40 -08:00
ftrace.c ftrace: Introduce and use ENTRIES_PER_PAGE_GROUP macro 2026-01-26 17:45:12 -05:00
ftrace_internal.h function_graph: Make fgraph_update_pid_func() a stub for !DYNAMIC_FTRACE 2024-06-10 18:08:23 -04:00
Kconfig tracing: Better separate SNAPSHOT and MAX_TRACE options 2026-02-08 21:01:13 -05:00
kprobe_event_gen_test.c
Makefile tracing: Move pid filtering into trace_pid.c 2026-02-08 21:01:13 -05:00
pid_list.c trace/pid_list: optimize pid_list->lock contention 2025-11-13 15:15:54 -05:00
pid_list.h trace/pid_list: optimize pid_list->lock contention 2025-11-13 15:15:54 -05:00
power-traces.c PM: cpufreq: powernv/tracing: Move powernv_throttle trace event 2025-07-21 16:40:56 -04:00
preemptirq_delay_test.c kernel: trace: preemptirq_delay_test: use offstack cpu mask 2025-07-08 18:17:38 -04:00
rethook.c rethook: honor CONFIG_FTRACE_VALIDATE_RCU_IS_WATCHING in rethook_try_get() 2024-05-01 23:18:48 +09:00
ring_buffer.c ring-buffer: Use a housekeeping CPU to wake up waiters 2026-01-26 17:44:53 -05:00
ring_buffer_benchmark.c tracing: Fix typo in ring_buffer_benchmark.c 2025-12-05 15:43:40 -05:00
rpm-traces.c
synth_event_gen_test.c tracing / synthetic: Disable events after testing in synth_event_gen_test_init() 2023-12-21 10:04:45 -05:00
trace.c tracing: Better separate SNAPSHOT and MAX_TRACE options 2026-02-08 21:01:13 -05:00
trace.h tracing: Better separate SNAPSHOT and MAX_TRACE options 2026-02-08 21:01:13 -05:00
trace_benchmark.c tracing: Improve benchmark test performance by using do_div() 2024-05-13 20:00:57 -04:00
trace_benchmark.h
trace_boot.c tracing: Allow creating instances with specified system events 2023-12-18 23:14:16 -05:00
trace_branch.c tracing: branch: Use trace_tracing_is_on_cpu() instead of "disabled" field 2025-05-09 15:19:10 -04:00
trace_btf.c tracing/probes: Fix to search structure fields correctly 2024-02-17 21:25:42 +09:00
trace_btf.h tracing/probes: Add a function to search a member of a struct/union 2023-08-23 09:40:16 +09:00
trace_clock.c tracing: Use atomic64_inc_return() in trace_clock_counter() 2024-10-09 19:59:49 -04:00
trace_dynevent.c tracing: Report wrong dynamic event command 2025-11-10 19:26:14 -05:00
trace_dynevent.h tracing: probes: Fix a possible race in trace_probe_log APIs 2025-05-13 22:23:34 +09:00
trace_entries.h function_graph: Enable funcgraph-args and funcgraph-retaddr to work simultaneously 2025-11-26 15:13:30 -05:00
trace_eprobe.c Probes for v6.19 2025-12-05 10:55:47 -08:00
trace_event_perf.c perf: Remove unnecessary parameter of security check 2025-02-26 14:13:58 -05:00
trace_events.c tracing: Make tracing_disabled global for tracing system 2026-02-08 21:01:11 -05:00
trace_events_filter.c tracing: Replace use of system_wq with system_dfl_wq 2026-01-26 17:44:05 -05:00
trace_events_filter_test.h
trace_events_hist.c tracing: Move tracing_set_filter_buffering() into trace_events_hist.c 2026-02-08 21:01:11 -05:00
trace_events_inject.c tracing: Have format file honor EVENT_FILE_FL_FREED 2024-08-07 18:12:46 -04:00
trace_events_synth.c tracing: Remove notrace from trace_event_raw_event_synth() 2026-01-28 21:01:09 -05:00
trace_events_trigger.c tracing: Have all triggers expect a file parameter 2026-02-08 21:00:57 -05:00
trace_events_user.c tracing: Fix multiple typos in trace_events_user.c 2025-12-05 15:43:41 -05:00
trace_export.c tracing: Add back FORTIFY_SOURCE logic to kernel_stack event structure 2023-07-30 18:11:44 -04:00
trace_fprobe.c tracing updates for v6.19: 2025-12-05 09:51:37 -08:00
trace_functions.c tracing: Have function tracer define options per instance 2025-11-12 09:59:54 -05:00
trace_functions_graph.c function_graph: Fix args pointer mismatch in print_graph_retval() 2026-01-23 13:34:38 -05:00
trace_hwlat.c tracing: Replace opencoded cpumask_next_wrap() in move_to_next_cpu() 2025-07-08 18:17:29 -04:00
trace_irqsoff.c tracing: Allow tracer to add more than 32 options 2025-11-04 21:44:00 +09:00
trace_kdb.c tracing: Allow tracer to add more than 32 options 2025-11-04 21:44:00 +09:00
trace_kprobe.c tracing: Make tracing_disabled global for tracing system 2026-02-08 21:01:11 -05:00
trace_kprobe_selftest.c tracing: arm64: Avoid missing-prototype warnings 2023-07-12 12:06:04 -04:00
trace_kprobe_selftest.h
trace_mmiotrace.c tracing/mmiotrace: Remove reference to unused per CPU data pointer 2025-05-08 09:36:09 -04:00
trace_nop.c
trace_osnoise.c tracing: Fix multiple typos in trace_osnoise.c 2025-12-05 15:43:41 -05:00
trace_output.c tracing: Add bitmask-list option for human-readable bitmask display 2026-01-26 17:00:50 -05:00
trace_output.h tracing: Allow tracer to add more than 32 options 2025-11-04 21:44:00 +09:00
trace_pid.c tracing: Move pid filtering into trace_pid.c 2026-02-08 21:01:13 -05:00
trace_preemptirq.c tracing: Fix archs that still call tracepoints without RCU watching 2024-12-05 09:28:58 -05:00
trace_printk.c tracing: Move trace_printk functions out of trace.c and into trace_printk.c 2026-02-08 21:01:12 -05:00
trace_probe.c tracing fixes for v6.19: 2025-12-06 13:49:40 -08:00
trace_probe.h tracing: probes: Use __free() for trace_probe_log 2025-11-01 01:10:28 +09:00
trace_probe_kernel.h tracing/probes: Fix to record 0-length data_loc in fetch_store_string*() if fails 2023-07-14 17:04:58 +09:00
trace_probe_tmpl.h tracing/fprobe: Enable fprobe events with CONFIG_DYNAMIC_FTRACE_WITH_ARGS 2024-12-26 10:50:04 -05:00
trace_recursion_record.c
trace_sched_switch.c tracing: Ensure optimized hashing works 2025-09-30 17:27:58 -04:00
trace_sched_wakeup.c tracing: Allow tracer to add more than 32 options 2025-11-04 21:44:00 +09:00
trace_selftest.c tracing: Rename trace_array field max_buffer to snapshot_buffer 2026-02-08 21:01:13 -05:00
trace_selftest_dynamic.c
trace_seq.c tracing: Add bitmask-list option for human-readable bitmask display 2026-01-26 17:00:50 -05:00
trace_stack.c tracing updates for v6.16: 2025-05-29 21:04:36 -07:00
trace_stat.c tracing: Switch trace_stat.c code over to use guard() 2024-12-26 10:38:37 -05:00
trace_stat.h
trace_synth.h
trace_syscalls.c tracing: Hide __NR_utimensat and _NR_mq_timedsend when not defined 2025-11-10 14:23:53 -05:00
trace_uprobe.c tracing: uprobe: eprobes: Allocate traceprobe_parse_context per probe 2025-11-01 01:10:29 +09:00
tracing_map.c tracing: Use vmalloc_array() to improve code 2025-09-23 09:31:58 -04:00
tracing_map.h tracing: Remove unused extern declaration tracing_map_set_field_descr() 2023-07-23 11:08:14 -04:00