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aa748949b4
linux/kernel/trace
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Daniel Bristot de Oliveira aa748949b4 tracing/timerlat: Notify IRQ new max latency only if stop tracing is set 
Currently, the notification of a new max latency is sent from
timerlat's IRQ handler anytime a new max latency is found.

While this behavior is not wrong, the send IPI overhead itself
will increase the thread latency and that is not the desired
effect (tracing overhead).

Moreover, the thread will notify a new max latency again because
the thread latency as it is always higher than the IRQ latency
that woke it up.

The only case in which it is helpful to notify a new max latency
from IRQ is when stop tracing (for the IRQ) is set, as in this
case, the thread will not be dispatched.

Notify a new max latency from the IRQ handler only if stop tracing is
set for the IRQ handler.

Link: https://lkml.kernel.org/r/2c2d9a56c0886c8402ba320de32856cbbb10c2bb.1652175637.git.bristot@kernel.org

Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Reported-by: Clark Williams <williams@redhat.com>
Fixes: a955d7eac1 ("trace: Add timerlat tracer")
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2022-05-26 21:13:00 -04:00
..
blktrace.c SCSI misc on 20220324 2022-03-24 19:37:53 -07:00
bpf_trace.c bpf: Fix sparse warnings in kprobe_multi_resolve_syms 2022-03-30 14:10:06 +02:00
bpf_trace.h
error_report-traces.c tracing: add error_report_end trace point 2021-02-26 09:41:02 -08:00
fgraph.c ftrace: Make ftrace_graph_is_dead() a static branch 2022-04-02 08:40:09 -04:00
fprobe.c fprobe: Fix sparse warning for acccessing __rcu ftrace_hash 2022-03-28 19:05:40 -07:00
ftrace_internal.h
ftrace.c ftrace: Deal with error return code of the ftrace_process_locs() function 2022-05-26 21:12:59 -04:00
Kconfig tracing: mark user_events as BROKEN 2022-04-02 10:32:14 -07:00
kprobe_event_gen_test.c
Makefile Networking changes for 5.18. 2022-03-24 13:13:26 -07:00
pid_list.c tracing: Cleanup double word in comment 2022-04-26 17:58:50 -04:00
pid_list.h tracing: Create a sparse bitmask for pid filtering 2021-10-05 17:38:45 -04:00
power-traces.c
preemptirq_delay_test.c kernel: trace: preemptirq_delay_test: add cpu affinity 2021-02-02 17:02:07 -05:00
rethook.c rethook: Fix to use WRITE_ONCE() for rethook:: Handler 2022-03-30 19:28:17 -07:00
ring_buffer_benchmark.c
ring_buffer.c ring-buffer: Have 32 bit time stamps use all 64 bits 2022-04-27 17:19:30 -04:00
rpm-traces.c
synth_event_gen_test.c tracing: Fix various typos in comments 2021-03-23 14:08:18 -04:00
trace_benchmark.c tracing: Fix some typos in comments 2020-11-10 20:39:40 -05:00
trace_benchmark.h
trace_boot.c tracing: Fix missing trace_boot_init_histograms kstrdup NULL checks 2021-10-26 09:18:10 -04:00
trace_branch.c tracing: Merge irqflags + preempt counter. 2021-02-02 17:02:06 -05:00
trace_clock.c tracing: Do no increment trace_clock_global() by one 2021-06-18 09:10:00 -04:00
trace_dynevent.c tracing: Use trace_create_file() to simplify creation of tracefs entries 2022-05-26 21:12:52 -04:00
trace_dynevent.h tracing: Add DYNAMIC flag for dynamic events 2021-08-18 18:10:32 -04:00
trace_entries.h trace: Add timerlat tracer 2021-06-25 19:57:24 -04:00
trace_eprobe.c tracing: Remove check of list iterator against head past the loop body 2022-04-27 17:19:31 -04:00
trace_event_perf.c tracing: Show size of requested perf buffer 2021-10-27 12:25:09 -04:00
trace_events_filter_test.h
trace_events_filter.c tracing: Add ustring operation to filtering string pointers 2022-01-14 03:42:24 -05:00
trace_events_hist.c tracing: Fix potential double free in create_var_ref() 2022-05-26 21:12:59 -04:00
trace_events_inject.c tracing: Support __rel_loc relative dynamic data location attribute 2021-12-06 15:37:21 -05:00
trace_events_synth.c tracing: Fix strncpy warning in trace_events_synth.c 2022-03-11 11:49:24 -05:00
trace_events_trigger.c tracing: Replace usage of found with dedicated list iterator variable 2022-04-27 17:19:31 -04:00
trace_events_user.c tracing: mark user_events as BROKEN 2022-04-02 10:32:14 -07:00
trace_events.c tracing: Use trace_create_file() to simplify creation of tracefs entries 2022-05-26 21:12:52 -04:00
trace_export.c tracing: Fix some typos in comments 2020-11-10 20:39:40 -05:00
trace_functions_graph.c tracing: in_irq() cleanup 2021-10-13 18:19:41 -04:00
trace_functions.c ftrace: disable preemption when recursion locked 2021-10-27 11:21:49 -04:00
trace_hwlat.c trace/hwlat: make use of the helper function kthread_run_on_cpu() 2022-01-15 16:30:24 +02:00
trace_irqsoff.c tracing: Merge irqflags + preempt counter. 2021-02-02 17:02:06 -05:00
trace_kdb.c kdb: Rename members of struct kdbtab_t 2021-07-27 17:05:06 +01:00
trace_kprobe_selftest.c
trace_kprobe_selftest.h
trace_kprobe.c tracing: Use trace_create_file() to simplify creation of tracefs entries 2022-05-26 21:12:52 -04:00
trace_mmiotrace.c tracing: Remove definition of DEBUG in trace_mmiotrace.c 2021-02-02 17:02:07 -05:00
trace_nop.c
trace_osnoise.c tracing/timerlat: Notify IRQ new max latency only if stop tracing is set 2022-05-26 21:13:00 -04:00
trace_output.c tracing: Remove usage of list iterator after the loop body 2022-04-27 17:19:30 -04:00
trace_output.h ftrace: Add recording of functions that caused recursion 2020-11-06 08:42:26 -05:00
trace_preemptirq.c lockdep: fix order in trace_hardirqs_off_caller() 2020-09-14 10:08:07 +02:00
trace_printk.c tracing: Disable "other" permission bits in the tracefs files 2021-10-08 18:08:43 -04:00
trace_probe_tmpl.h tracing/probes: Have process_fetch_insn() take a void * instead of pt_regs 2021-08-19 09:09:03 -04:00
trace_probe.c eprobes: Remove redundant event type information 2022-02-25 12:07:01 -05:00
trace_probe.h eprobes: Remove redundant event type information 2022-02-25 12:07:01 -05:00
trace_recursion_record.c tracing: Use trace_create_file() to simplify creation of tracefs entries 2022-05-26 21:12:52 -04:00
trace_sched_switch.c Tracing updates for 5.18: 2022-03-23 11:40:25 -07:00
trace_sched_wakeup.c sched/tracing: Don't re-read p->state when emitting sched_switch event 2022-03-01 16:18:39 +01:00
trace_selftest_dynamic.c
trace_selftest.c tracing: Reset the function filter after completing trampoline/graph selftest 2022-05-25 16:57:37 -04:00
trace_seq.c tracing: Fix various typos in comments 2021-03-23 14:08:18 -04:00
trace_stack.c tracing: Disable "other" permission bits in the tracefs files 2021-10-08 18:08:43 -04:00
trace_stat.c tracing: Disable "other" permission bits in the tracefs files 2021-10-08 18:08:43 -04:00
trace_stat.h
trace_synth.h tracing: synth events: increase max fields count 2021-09-08 15:29:16 -04:00
trace_syscalls.c tracing: Make tp_printk work on syscall tracepoints 2022-04-26 17:58:52 -04:00
trace_uprobe.c Tracing updates for 5.17: 2022-01-16 10:15:32 +02:00
trace.c tracing: Fix return value of trace_pid_write() 2022-05-26 21:12:59 -04:00
trace.h tracing: Have existing event_command.parse() implementations use helpers 2022-04-26 17:58:50 -04:00
tracing_map.c tracing: Fix tracing_map_sort_entries() kernel-doc comment 2022-04-26 17:58:51 -04:00
tracing_map.h tracing: Fix some typos in comments 2020-11-10 20:39:40 -05:00