linux.git/kernel/trace, branch v6.3-rc5

Merge tag 'trace-v6.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2023-03-19T17:46:02+00:00

Pull tracing fixes from Steven Rostedt:

 - Fix setting affinity of hwlat threads in containers

   Using sched_set_affinity() has unwanted side effects when being
   called within a container. Use set_cpus_allowed_ptr() instead

 - Fix per cpu thread management of the hwlat tracer:
    - Do not start per_cpu threads if one is already running for the CPU
    - When starting per_cpu threads, do not clear the kthread variable
      as it may already be set to running per cpu threads

 - Fix return value for test_gen_kprobe_cmd()

   On error the return value was overwritten by being set to the result
   of the call from kprobe_event_delete(), which would likely succeed,
   and thus have the function return success

 - Fix splice() reads from the trace file that was broken by commit
   36e2c7421f02 ("fs: don't allow splice read/write without explicit
   ops")

 - Remove obsolete and confusing comment in ring_buffer.c

   The original design of the ring buffer used struct page flags for
   tricks to optimize, which was shortly removed due to them being
   tricks. But a comment for those tricks remained

 - Set local functions and variables to static

* tag 'trace-v6.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing/hwlat: Replace sched_setaffinity with set_cpus_allowed_ptr
  ring-buffer: remove obsolete comment for free_buffer_page()
  tracing: Make splice_read available again
  ftrace: Set direct_ops storage-class-specifier to static
  trace/hwlat: Do not start per-cpu thread if it is already running
  trace/hwlat: Do not wipe the contents of per-cpu thread data
  tracing/osnoise: set several trace_osnoise.c variables storage-class-specifier to static
  tracing: Fix wrong return in kprobe_event_gen_test.c

tracing/hwlat: Replace sched_setaffinity with set_cpus_allowed_ptr

2023-03-19T17:23:22+00:00

There is a problem with the behavior of hwlat in a container,
resulting in incorrect output. A warning message is generated:
"cpumask changed while in round-robin mode, switching to mode none",
and the tracing_cpumask is ignored. This issue arises because
the kernel thread, hwlatd, is not a part of the container, and
the function sched_setaffinity is unable to locate it using its PID.
Additionally, the task_struct of hwlatd is already known.
Ultimately, the function set_cpus_allowed_ptr achieves
the same outcome as sched_setaffinity, but employs task_struct
instead of PID.

Test case:

  # cd /sys/kernel/tracing
  # echo 0 > tracing_on
  # echo round-robin > hwlat_detector/mode
  # echo hwlat > current_tracer
  # unshare --fork --pid bash -c 'echo 1 > tracing_on'
  # dmesg -c

Actual behavior:

[573502.809060] hwlat_detector: cpumask changed while in round-robin mode, switching to mode none

Link: https://lore.kernel.org/linux-trace-kernel/20230316144535.1004952-1-costa.shul@redhat.com

Cc: Masami Hiramatsu 
Fixes: 0330f7aa8ee63 ("tracing: Have hwlat trace migrate across tracing_cpumask CPUs")
Signed-off-by: Costa Shulyupin 
Acked-by: Daniel Bristot de Oliveira 
Signed-off-by: Steven Rostedt (Google)

ring-buffer: remove obsolete comment for free_buffer_page()

2023-03-19T17:23:22+00:00

The comment refers to mm/slob.c which is being removed. It comes from
commit ed56829cb319 ("ring_buffer: reset buffer page when freeing") and
according to Steven the borrowed code was a page mapcount and mapping
reset, which was later removed by commit e4c2ce82ca27 ("ring_buffer:
allocate buffer page pointer"). Thus the comment is not accurate anyway,
remove it.

Link: https://lore.kernel.org/linux-trace-kernel/20230315142446.27040-1-vbabka@suse.cz

Cc: Masami Hiramatsu 
Cc: Ingo Molnar 
Reported-by: Mike Rapoport 
Suggested-by: Steven Rostedt (Google) 
Fixes: e4c2ce82ca27 ("ring_buffer: allocate buffer page pointer")
Signed-off-by: Vlastimil Babka 
Reviewed-by: Mukesh Ojha 
Signed-off-by: Steven Rostedt (Google)

tracing: Make splice_read available again

2023-03-19T17:16:21+00:00

Since the commit 36e2c7421f02 ("fs: don't allow splice read/write
without explicit ops") is applied to the kernel, splice() and
sendfile() calls on the trace file (/sys/kernel/debug/tracing
/trace) return EINVAL.

This patch restores these system calls by initializing splice_read
in file_operations of the trace file. This patch only enables such
functionalities for the read case.

Link: https://lore.kernel.org/linux-trace-kernel/20230314013707.28814-1-sfoon.kim@samsung.com

Cc: stable@vger.kernel.org
Fixes: 36e2c7421f02 ("fs: don't allow splice read/write without explicit ops")
Signed-off-by: Sung-hun Kim 
Signed-off-by: Steven Rostedt (Google)

ftrace: Set direct_ops storage-class-specifier to static

2023-03-19T16:20:49+00:00

smatch reports this warning
kernel/trace/ftrace.c:2594:19: warning:
  symbol 'direct_ops' was not declared. Should it be static?

The variable direct_ops is only used in ftrace.c, so it should be static

Link: https://lore.kernel.org/linux-trace-kernel/20230311135113.711824-1-trix@redhat.com

Signed-off-by: Tom Rix 
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Steven Rostedt (Google)

trace/hwlat: Do not start per-cpu thread if it is already running

2023-03-19T16:20:49+00:00

The hwlatd tracer will end up starting multiple per-cpu threads with
the following script:

    #!/bin/sh
    cd /sys/kernel/debug/tracing
    echo 0 > tracing_on
    echo hwlat > current_tracer
    echo per-cpu > hwlat_detector/mode
    echo 100000 > hwlat_detector/width
    echo 200000 > hwlat_detector/window
    echo 1 > tracing_on

To fix the issue, check if the hwlatd thread for the cpu is already
running, before starting a new one. Along with the previous patch, this
avoids running multiple instances of the same CPU thread on the system.

Link: https://lore.kernel.org/all/20230302113654.2984709-1-tero.kristo@linux.intel.com/
Link: https://lkml.kernel.org/r/20230310100451.3948583-3-tero.kristo@linux.intel.com

Cc: stable@vger.kernel.org
Fixes: f46b16520a087 ("trace/hwlat: Implement the per-cpu mode")
Signed-off-by: Tero Kristo 
Acked-by: Daniel Bristot de Oliveira 
Signed-off-by: Steven Rostedt (Google)

trace/hwlat: Do not wipe the contents of per-cpu thread data

2023-03-19T16:20:48+00:00

Do not wipe the contents of the per-cpu kthread data when starting the
tracer, as this will completely forget about already running instances
and can later start new additional per-cpu threads.

Link: https://lore.kernel.org/all/20230302113654.2984709-1-tero.kristo@linux.intel.com/
Link: https://lkml.kernel.org/r/20230310100451.3948583-2-tero.kristo@linux.intel.com

Cc: stable@vger.kernel.org
Fixes: f46b16520a087 ("trace/hwlat: Implement the per-cpu mode")
Signed-off-by: Tero Kristo 
Acked-by: Daniel Bristot de Oliveira 
Signed-off-by: Steven Rostedt (Google)

tracing/osnoise: set several trace_osnoise.c variables storage-class-specifier to static

2023-03-19T16:20:48+00:00

smatch reports several similar warnings
kernel/trace/trace_osnoise.c:220:1: warning:
  symbol '__pcpu_scope_per_cpu_osnoise_var' was not declared. Should it be static?
kernel/trace/trace_osnoise.c:243:1: warning:
  symbol '__pcpu_scope_per_cpu_timerlat_var' was not declared. Should it be static?
kernel/trace/trace_osnoise.c:335:14: warning:
  symbol 'interface_lock' was not declared. Should it be static?
kernel/trace/trace_osnoise.c:2242:5: warning:
  symbol 'timerlat_min_period' was not declared. Should it be static?
kernel/trace/trace_osnoise.c:2243:5: warning:
  symbol 'timerlat_max_period' was not declared. Should it be static?

These variables are only used in trace_osnoise.c, so it should be static

Link: https://lore.kernel.org/linux-trace-kernel/20230309150414.4036764-1-trix@redhat.com

Signed-off-by: Tom Rix 
Acked-by: Masami Hiramatsu (Google) 
Acked-by: Daniel Bristot de Oliveira 
Signed-off-by: Steven Rostedt (Google)

tracing: Fix wrong return in kprobe_event_gen_test.c

2023-03-19T16:20:48+00:00

Overwriting the error code with the deletion result may cause the
function to return 0 despite encountering an error. Commit b111545d26c0
("tracing: Remove the useless value assignment in
test_create_synth_event()") solves a similar issue by
returning the original error code, so this patch does the same.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Link: https://lore.kernel.org/linux-trace-kernel/20230131075818.5322-1-aagusev@ispras.ru

Signed-off-by: Anton Gusev 
Reviewed-by: Steven Rostedt (Google) 
Acked-by: Masami Hiramatsu (Google) 
Signed-off-by: Steven Rostedt (Google)

Merge tag 'trace-v6.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2023-03-15T00:07:54+00:00

Pull tracing fixes from Steven Rostedt:

 - Do not allow histogram values to have modifies. They can cause a NULL
   pointer dereference if they do.

 - Warn if hist_field_name() is passed a NULL. Prevent the NULL pointer
   dereference mentioned above.

 - Fix invalid address look up race in lookup_rec()

 - Define ftrace_stub_graph conditionally to prevent linker errors

 - Always check if RCU is watching at all tracepoint locations

* tag 'trace-v6.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing: Make tracepoint lockdep check actually test something
  ftrace,kcfi: Define ftrace_stub_graph conditionally
  ftrace: Fix invalid address access in lookup_rec() when index is 0
  tracing: Check field value in hist_field_name()
  tracing: Do not let histogram values have some modifiers