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4e8729e659
linux/kernel/trace
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Steven Rostedt 4e8729e659 ring-buffer: Better comment the use of RB_MISSED_EVENTS 
If the persistent ring buffer is detected on boot up to have a corrupted
sub-buffer, that sub-buffer is cleared to zero and its commit value has
the RB_MISSED_EVENTS bit set. That bit is to allow the "trace",
"trace_pipe" and "trace_pipe_raw" files know that events were dropped by
outputting "[LOST EVENTS]".

Only in this case does that bit get set in the writeable portion of the
ring buffer. When events are dropped in the normal ring buffer, that
information is stored in the cpu_buffer descriptor and the
RB_MISSED_EVENTS is set in the buffer page at the time the page is
consumed. It is never set in the writeable portion of the buffer.

Add comments to describe this better as it can be confusing to know when
the RB_MISSED_EVENTS are set in the commit portion of the buffer page.

Link: https://lore.kernel.org/all/20260529001500.14178455a046a5cbc6180861@kernel.org/

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Link: https://patch.msgid.link/20260528223738.41276c0e@fedora
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2026-05-31 20:34:05 -04:00
..
rv rv: Allow epoll in rtapp-sleep monitor 2026-04-01 15:18:30 +02:00
blktrace.c block-7.0-20260305 2026-03-06 08:36:18 -08:00
bpf_trace.c fprobe: Fix unregister_fprobe() to wait for RCU grace period 2026-05-11 19:04:46 +09:00
bpf_trace.h
error_report-traces.c
fgraph.c fgraph: Do not call handlers direct when not using ftrace_ops 2026-02-19 15:21:22 -05:00
fprobe.c fprobe: Fix unregister_fprobe() to wait for RCU grace period 2026-05-11 19:04:46 +09:00
ftrace_internal.h
ftrace.c tracing updates for v7.1: 2026-04-17 09:43:12 -07:00
Kconfig ring-buffer: Add persistent ring buffer invalid-page inject test 2026-05-28 22:40:51 -04:00
kprobe_event_gen_test.c
Makefile tracing: Create output file from cmd_check_undefined 2026-05-21 08:31:55 -04:00
pid_list.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
pid_list.h
power-traces.c
preemptirq_delay_test.c
remote_test_events.h tracing: Add a trace remote module for testing 2026-03-09 12:33:55 -04:00
remote_test.c tracing: Fix desc in error path for the trace remote test module 2026-05-16 16:11:04 -04:00
rethook.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
ring_buffer_benchmark.c
ring_buffer.c ring-buffer: Better comment the use of RB_MISSED_EVENTS 2026-05-31 20:34:05 -04:00
rpm-traces.c
simple_ring_buffer.c tracing: Fix unload_page for simple_ring_buffer init rollback 2026-05-21 08:26:22 -04:00
synth_event_gen_test.c
trace_benchmark.c
trace_benchmark.h
trace_boot.c tracing: Make the backup instance non-reusable 2026-04-02 13:20:38 -04:00
trace_branch.c tracing: branch: Fix inverted check on stat tracer registration 2026-04-28 14:28:29 -04:00
trace_btf.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_btf.h
trace_clock.c
trace_dynevent.c
trace_dynevent.h
trace_entries.h tracing: Fix ftrace event field alignments 2026-02-05 09:47:11 -05:00
trace_eprobe.c Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_event_perf.c
trace_events_filter_test.h
trace_events_filter.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_events_hist.c tracing: Avoid NULL return from hist_field_name() on truncation 2026-05-20 16:10:56 -04:00
trace_events_inject.c
trace_events_synth.c tracing: Use explicit array size instead of sentinel elements in symbol printing 2026-03-12 12:15:53 +01:00
trace_events_trigger.c tracing: Drain deferred trigger frees if kthread creation fails 2026-03-28 08:32:44 -04:00
trace_events_user.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_events.c tracing updates for v7.1: 2026-04-17 09:43:12 -07:00
trace_export.c tracing: Fix ftrace event field alignments 2026-02-05 09:47:11 -05:00
trace_fprobe.c Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_functions_graph.c fgraph: Fix thresh_return nosleeptime double-adjust 2026-03-03 22:11:20 -05:00
trace_functions.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_hwlat.c tracing: Fix false sharing in hwlat get_sample() 2026-02-10 03:36:39 -05:00
trace_irqsoff.c
trace_kdb.c
trace_kprobe_selftest.c
trace_kprobe_selftest.h
trace_kprobe.c tracing updates for v7.1: 2026-04-17 09:43:12 -07:00
trace_mmiotrace.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_nop.c
trace_osnoise.c tracing latency updates for 7.1: 2026-04-17 10:12:11 -07:00
trace_output.c tracing updates for v7.1: 2026-04-17 09:43:12 -07:00
trace_output.h
trace_pid.c tracing: Move pid filtering into trace_pid.c 2026-02-08 21:01:13 -05:00
trace_preemptirq.c
trace_printk.c tracing: move __printf() attribute on __ftrace_vbprintk() 2026-03-23 20:16:45 -04:00
trace_probe_kernel.h
trace_probe_tmpl.h
trace_probe.c tracing/probes: Limit size of event probe to 3K 2026-04-29 16:07:38 -04:00
trace_probe.h tracing/probes: Limit size of event probe to 3K 2026-04-29 16:07:38 -04:00
trace_recursion_record.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_remote.c tracing: Non-consuming read for trace remotes with an offline CPU 2026-04-02 14:16:09 +01:00
trace_sched_switch.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_sched_wakeup.c
trace_selftest_dynamic.c
trace_selftest.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_seq.c tracing: Add bitmask-list option for human-readable bitmask display 2026-01-26 17:00:50 -05:00
trace_snapshot.c tracing: Remove duplicate latency_fsnotify() stub 2026-03-31 14:58:39 -04:00
trace_stack.c
trace_stat.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace_stat.h
trace_synth.h
trace_syscalls.c tracing: Use explicit array size instead of sentinel elements in symbol printing 2026-03-12 12:15:53 +01:00
trace_uprobe.c Convert 'alloc_flex' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
trace.c ring-buffer: Add persistent ring buffer invalid-page inject test 2026-05-28 22:40:51 -04:00
trace.h tracing updates for v7.1: 2026-04-17 09:43:12 -07:00
tracing_map.c tracing: Do not call map->ops->elt_free() if elt_alloc() fails 2026-05-21 11:29:03 -04:00
tracing_map.h
undefsyms_base.c tracing: Make undefsyms_base.c a first-class citizen 2026-04-22 11:24:41 -04:00