Merge tag 'trace-v7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

3c6e577d · Linus Torvalds <[email protected]> · 2026-02-13 19:25:16 -08:00

Pull tracing updates from Steven Rostedt:
 "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"

* tag 'trace-v7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (46 commits)
  function_graph: Restore direct mode when callbacks drop to one
  tracing: Fix indentation of return statement in print_trace_fmt()
  tracing: Reset last_boot_info if ring buffer is reset
  tracing: Fix to set write permission to per-cpu buffer_size_kb
  tracing: Fix false sharing in hwlat get_sample()
  tracing: Move d_max_latency out of CONFIG_FSNOTIFY protection
  tracing: Better separate SNAPSHOT and MAX_TRACE options
  tracing: Add tracer_uses_snapshot() helper to remove #ifdefs
  tracing: Rename trace_array field max_buffer to snapshot_buffer
  tracing: Move pid filtering into trace_pid.c
  tracing: Move trace_printk functions out of trace.c and into trace_printk.c
  tracing: Use system_state in trace_printk_init_buffers()
  tracing: Have trace_printk functions use flags instead of using global_trace
  tracing: Make tracing_update_buffers() take NULL for global_trace
  tracing: Make printk_trace global for tracing system
  tracing: Move ftrace_trace_stack() out of trace.c and into trace.h
  tracing: Move __trace_buffer_{un}lock_*() functions to trace.h
  tracing: Make tracing_selftest_running global to the tracing subsystem
  tracing: Make tracing_disabled global for tracing system
  tracing: Clean up use of trace_create_maxlat_file()
  ...

Commit

3c6e577d5ae705edebed9882ff474d7a48a47dd2

Parents

f50822fd · 53b2fae9

Merge commit. Changes below are compared with the first parent: f50822fd.

Changes

31 files changed · +1388 −1073