[GIT PULL] tracing updates for v7.0

[Steven Rostedt]

Linus,

[
  Note, there's two merge conflicts:

    1. With BPF code. This PR made tracepoint callbacks preemptable. BPF
       needs to run on the same CPU until completion. Alexei recommended
       using rcu_read_lock_dont_migrate() in the BPF callback. This
       conflicted with some other changes in the BPF tree.

    2. With mm tree. This PR moved trace_printk() code out of trace.c and
       into trace_printk.c. A change in Andrew Morton's mm tree removed the
       string size parameter from __trace_puts(). That function was one of
       the functions moved to trace_printk.c. That update now needs to
       happen in that file instead.

   The updates in linux-next master branch have the proper merge resolution.
]

tracing updates for 7.0:

User visible changes:

- Add an entry into MAINTAINERS file for RUST versions of code

  There's now RUST code for tracing and static branches. To differentiate
  that code from the C code, add entries in for the RUST version (with "[RUST]"
  around it) so that the right maintainers get notified on changes.

- New bitmask-list option added to tracefs

  When this is set, bitmasks in trace event are not displayed as hex
  numbers, but instead as lists: e.g. 0-5,7,9 instead of 0000015f

- New show_event_filters file in tracefs

  Instead of having to search all events/*/*/filter for any active filters
  enabled in the trace instance, the file show_event_filters will list them
  so that there's only one file that needs to be examined to see if any
  filters are active.

- New show_event_triggers file in tracefs

  Instead of having to search all events/*/*/trigger for any active triggers
  enabled in the trace instance, the file show_event_triggers will list them
  so that there's only one file that needs to be examined to see if any
  triggers are active.

- Have traceoff_on_warning disable trace pintk buffer too

  Recently recording of trace_printk() could go to other trace instances
  instead of the top level instance. But if traceoff_on_warning triggers, it
  doesn't stop the buffer with trace_printk() and that data can easily be
  lost by being overwritten. Have traceoff_on_warning also disable the
  instance that has trace_printk() being written to it.

- Update the hist_debug file to show what function the field uses

  When CONFIG_HIST_TRIGGERS_DEBUG is enabled, a hist_debug file exists for
  every event. This displays the internal data of any histogram enabled for
  that event. But it is lacking the function that is called to process one
  of its fields. This is very useful information that was missing when
  debugging histograms.

- Up the histogram stack size from 16 to 31

  Stack traces can be used as keys for event histograms. Currently the size
  of the stack that is stored is limited to just 16 entries. But the storage
  space in the histogram is 256 bytes, meaning that it can store up to 31
  entries (plus one for the count of entries). Instead of letting that space
  go to waste, up the limit from 16 to 31. This makes the keys much more
  useful.

- Fix permissions of per CPU file buffer_size_kb

  The per CPU file of buffer_size_kb was incorrectly set to read only in a
  previous cleanup. It should be writable.

- Reset "last_boot_info" if the persistent buffer is cleared

  The last_boot_info shows address information of a persistent ring buffer
  if it contains data from a previous boot. It is cleared when recording
  starts again, but it is not cleared when the buffer is reset. The data is
  useless after a reset so clear it on reset too.

Internal changes:

- A change was made to allow tracepoint callbacks to have preemption
  enabled, and instead be protected by SRCU. This required some updates to
  the callbacks for perf and BPF.

  perf needed to disable preemption directly in its callback because it
  expects preemption disabled in the later code.

  BPF needed to disable migration, as its code expects to run completely on
  the same CPU.

- Have irq_work wake up other CPU if current CPU is "isolated"

  When there's a waiter waiting on ring buffer data and a new event happens,
  an irq work is triggered to wake up that waiter. This is noisy on isolated
  CPUs (running NO_HZ_FULL). Trigger an IPI to a house keeping CPU instead.

- Use proper free of trigger_data instead of open coding it in.

- Remove redundant call of event_trigger_reset_filter()

  It was called immediately in a function that was called right after it.

- Workqueue cleanups

- Report errors if tracing_update_buffers() were to fail.

- Make the enum update workqueue generic for other parts of tracing

  On boot up, a work queue is created to convert enum names into their
  numbers in the trace event format files. This work queue can also be used
  for other aspects of tracing that takes some time and shouldn't be called
  by the init call code.

  The blk_trace initialization takes a bit of time. Have the initialization
  code moved to the new tracing generic work queue function.

- Skip kprobe boot event creation call if there's no kprobes defined on cmdline

  The kprobe initialization to set up kprobes if they are defined on the
  cmdline requires taking the event_mutex lock. This can be held by other
  tracing code doing initialization for a long time. Since kprobes added to
  the kernel command line need to be setup immediately, as they may be
  tracing early initialization code, they cannot be postponed in a work
  queue and must be setup in the initcall code.

  If there's no kprobe on the kernel cmdline, there's no reason to take the
  mutex and slow down the boot up code waiting to get the lock only to find
  out there's nothing to do. Simply exit out early if there's no kprobes on
  the kernel cmdline.

  If there are kprobes on the cmdline, then someone cares more about tracing
  over the speed of boot up.

- Clean up the trigger code a bit

- Move code out of trace.c and into their own files

  trace.c is now over 11,000 lines of code and has become more difficult to
  maintain. Start splitting it up so that related code is in their own
  files.

  Move all the trace_printk() related code into trace_printk.c.

  Move the __always_inline stack functions into trace.h.

  Move the pid filtering code into a new trace_pid.c file.

- Better define the max latency and snapshot code

  The latency tracers have a "max latency" buffer that is a copy of the main
  buffer and gets swapped with it when a new high latency is detected. This
  keeps the trace up to the highest latency around where this max_latency
  buffer is never written to. It is only used to save the last max latency
  trace.

  A while ago a snapshot feature was added to tracefs to allow user space to
  perform the same logic. It could also enable events to trigger a
  "snapshot" if one of their fields hit a new high. This was built on top of
  the latency max_latency buffer logic.

  Because snapshots came later, they were dependent on the latency tracers
  to be enabled. In reality, the latency tracers depend on the snapshot code
  and not the other way around. It was just that they came first.

  Restructure the code and the kconfigs to have the latency tracers depend
  on snapshot code instead. This actually simplifies the logic a bit and
  allows to disable more when the latency tracers are not defined and the
  snapshot code is.

- Fix a "false sharing" in the hwlat tracer code

  The loop to search for latency in hardware was using a variable that could
  be changed by user space for each sample. If the user change this
  variable, it could cause a bus contention, and reading that variable can
  show up as a large latency in the trace causing a false positive. Read
  this variable at the start of the sample with a READ_ONCE() into a local
  variable and keep the code from sharing cache lines with readers.

- Fix function graph tracer static branch optimization code

  When only one tracer is defined for function graph tracing, it uses a
  static branch to call that tracer directly. When another tracer is added,
  it goes into loop logic to call all the registered callbacks.

  The code was incorrect when going back to one tracer and never re-enabled
  the static branch again to do the optimization code.

- And other small fixes and cleanups.


Please pull the latest trace-v7.0 tree, which can be found at:


  git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
trace-v7.0

Tag SHA1: 550103013647f1293433ce34d38faa20b0aeb8c9
Head SHA1: 53b2fae90ff01fede6520ca744ed5e8e366497ba


Aaron Tomlin (3):
      tracing: Add bitmask-list option for human-readable bitmask display
      tracing: Add show_event_filters to expose active event filters
      tracing: Add show_event_triggers to expose active event triggers

Alice Ryhl (1):
      MAINTAINERS: add Rust files to STATIC BRANCH/CALL and TRACING

Colin Lord (1):
      tracing: Fix false sharing in hwlat get_sample()

Guenter Roeck (1):
      ftrace: Introduce and use ENTRIES_PER_PAGE_GROUP macro

Haoyang LIU (1):
      tracing: Fix indentation of return statement in print_trace_fmt()

Marco Crivellari (1):
      tracing: Replace use of system_wq with system_dfl_wq

Masami Hiramatsu (Google) (2):
      tracing: Fix to set write permission to per-cpu buffer_size_kb
      tracing: Reset last_boot_info if ring buffer is reset

Miaoqian Lin (1):
      tracing: Properly process error handling in event_hist_trigger_parse()

Paul E. McKenney (1):
      srcu: Fix warning to permit SRCU-fast readers in NMI handlers

Petr Tesarik (1):
      ring-buffer: Use a housekeeping CPU to wake up waiters

Shengming Hu (1):
      function_graph: Restore direct mode when callbacks drop to one

Steven Rostedt (29):
      tracing: Remove redundant call to event_trigger_reset_filter() in event_hist_trigger_parse()
      tracing: Check the return value of tracing_update_buffers()
      tracing: Have show_event_trigger/filter format a bit more in columns
      tracing: Disable trace_printk buffer on warning too
      tracing: Have hist_debug show what function a field uses
      tracing: Remove notrace from trace_event_raw_event_synth()
      tracing: Up the hist stacktrace size from 16 to 31
      tracing: Remove duplicate ENABLE_EVENT_STR and DISABLE_EVENT_STR macros
      tracing: perf: Have perf tracepoint callbacks always disable preemption
      bpf: Have __bpf_trace_run() use rcu_read_lock_dont_migrate()
      tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast
      tracing: Add kerneldoc to trace_event_buffer_reserve()
      tracing: Have all triggers expect a file parameter
      tracing: Move tracing_set_filter_buffering() into trace_events_hist.c
      tracing: Clean up use of trace_create_maxlat_file()
      tracing: Make tracing_disabled global for tracing system
      tracing: Make tracing_selftest_running global to the tracing subsystem
      tracing: Move __trace_buffer_{un}lock_*() functions to trace.h
      tracing: Move ftrace_trace_stack() out of trace.c and into trace.h
      tracing: Make printk_trace global for tracing system
      tracing: Make tracing_update_buffers() take NULL for global_trace
      tracing: Have trace_printk functions use flags instead of using global_trace
      tracing: Use system_state in trace_printk_init_buffers()
      tracing: Move trace_printk functions out of trace.c and into trace_printk.c
      tracing: Move pid filtering into trace_pid.c
      tracing: Rename trace_array field max_buffer to snapshot_buffer
      tracing: Add tracer_uses_snapshot() helper to remove #ifdefs
      tracing: Better separate SNAPSHOT and MAX_TRACE options
      tracing: Move d_max_latency out of CONFIG_FSNOTIFY protection

Yaxiong Tian (3):
      tracing: Rename `eval_map_wq` and allow other parts of tracing use it
      blktrace: Make init_blk_tracer() asynchronous
      tracing/kprobes: Skip setup_boot_kprobe_events() when no cmdline event

----
 Documentation/trace/ftrace.rst             |   25 +
 MAINTAINERS                                |   15 +
 include/linux/trace_events.h               |    8 +-
 include/linux/trace_seq.h                  |   12 +-
 include/linux/tracepoint.h                 |    9 +-
 include/trace/perf.h                       |    4 +-
 include/trace/stages/stage3_trace_output.h |    4 +-
 include/trace/trace_events.h               |    4 +-
 kernel/rcu/srcutree.c                      |    3 +-
 kernel/trace/Kconfig                       |    8 +-
 kernel/trace/Makefile                      |    1 +
 kernel/trace/blktrace.c                    |   23 +-
 kernel/trace/bpf_trace.c                   |    5 +-
 kernel/trace/fgraph.c                      |    2 +-
 kernel/trace/ftrace.c                      |    7 +-
 kernel/trace/ring_buffer.c                 |   24 +-
 kernel/trace/trace.c                       | 1059 ++++------------------------
 kernel/trace/trace.h                       |  131 +++-
 kernel/trace/trace_events.c                |  163 ++++-
 kernel/trace/trace_events_filter.c         |    2 +-
 kernel/trace/trace_events_hist.c           |  101 ++-
 kernel/trace/trace_events_synth.c          |    6 +-
 kernel/trace/trace_events_trigger.c        |   62 +-
 kernel/trace/trace_hwlat.c                 |   15 +-
 kernel/trace/trace_kprobe.c                |    6 +-
 kernel/trace/trace_output.c                |   30 +-
 kernel/trace/trace_pid.c                   |  246 +++++++
 kernel/trace/trace_printk.c                |  431 +++++++++++
 kernel/trace/trace_selftest.c              |   10 +-
 kernel/trace/trace_seq.c                   |   29 +-
 kernel/tracepoint.c                        |   18 +-
 31 files changed, 1389 insertions(+), 1074 deletions(-)
 create mode 100644 kernel/trace/trace_pid.c
---------------------------