linux-toradex.git/kernel/trace/rv, branch v6.17-rc2

Merge tag 'trace-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

2025-08-01T17:29:36+00:00

Pull tracing updates from Steven Rostedt:

- Deprecate auto-mounting tracefs to /sys/kernel/debug/tracing

When tracefs was first introduced back in 2014, the directory
/sys/kernel/tracing was added and is the designated location to mount
tracefs. To keep backward compatibility, tracefs was auto-mounted in
/sys/kernel/debug/tracing as well.

All distros now mount tracefs on /sys/kernel/tracing. Having it seen
in two different locations has lead to various issues and
inconsistencies.

The VFS folks have to also maintain debugfs_create_automount() for
this single user.

It's been over 10 years. Tooling and scripts should start replacing
the debugfs location with the tracefs one. The reason tracefs was
created in the first place was to allow access to the tracing
facilities without the need to configure debugfs into the kernel.
Using tracefs should now be more robust.

A new config is created: CONFIG_TRACEFS_AUTOMOUNT_DEPRECATED which is
default y, so that the kernel is still built with the automount. This
config allows those that want to remove the automount from debugfs to
do so.

When tracefs is accessed from /sys/kernel/debug/tracing, the
following printk is triggerd:

pr_warn("NOTICE: Automounting of tracing to debugfs is deprecated and will be removed in 2030\n");

This gives users another 5 years to fix their scripts.

- Use queue_rcu_work() instead of call_rcu() for freeing event filters

The number of filters to be free can be many depending on the number
of events within an event system. Freeing them from softirq context
can potentially cause undesired latency. Use the RCU workqueue to
free them instead.

- Remove pointless memory barriers in latency code

Memory barriers were added to some of the latency code a long time
ago with the idea of "making them visible", but that's not what
memory barriers are for. They are to synchronize access between
different variables. There was no synchronization here making them
pointless.

- Remove "__attribute__()" from the type field of event format

When LLVM is used to compile the kernel with CONFIG_DEBUG_INFO_BTF=y
and PAHOLE_HAS_BTF_TAG=y, some of the format fields get expanded with
the following:

field:const char * filename; offset:24; size:8; signed:0;

Turns into:

field:const char __attribute__((btf_type_tag("user"))) * filename; offset:24; size:8; signed:0;

This confuses parsers. Add code to strip these tags from the strings.

- Add eprobe config option CONFIG_EPROBE_EVENTS

Eprobes were added back in 5.15 but were only enabled when another
probe was enabled (kprobe, fprobe, uprobe, etc). The eprobes had no
config option of their own. Add one as they should be a separate
entity.

It's default y to keep with the old kernels but still has
dependencies on TRACING and HAVE_REGS_AND_STACK_ACCESS_API.

- Add eprobe documentation

When eprobes were added back in 5.15 no documentation was added to
describe them. This needs to be rectified.

- Replace open coded cpumask_next_wrap() in move_to_next_cpu()

- Have preemptirq_delay_run() use off-stack CPU mask

- Remove obsolete comment about pelt_cfs event

DECLARE_TRACE() appends "_tp" to trace events now, but the comment
above pelt_cfs still mentioned appending it manually.

- Remove EVENT_FILE_FL_SOFT_MODE flag

The SOFT_MODE flag was required when the soft enabling and disabling
of trace events was first introduced. But there was a bug with this
approach as it only worked for a single instance. When multiple users
required soft disabling and disabling the code was changed to have a
ref count. The SOFT_MODE flag is now set iff the ref count is non
zero. This is redundant and just reading the ref count is good
enough.

- Fix typo in comment

* tag 'trace-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
Documentation: tracing: Add documentation about eprobes
tracing: Have eprobes have their own config option
tracing: Remove "__attribute__()" from the type field of event format
tracing: Deprecate auto-mounting tracefs in debugfs
tracing: Fix comment in trace_module_remove_events()
tracing: Remove EVENT_FILE_FL_SOFT_MODE flag
tracing: Remove pointless memory barriers
tracing/sched: Remove obsolete comment on suffixes
kernel: trace: preemptirq_delay_test: use offstack cpu mask
tracing: Use queue_rcu_work() to free filters
tracing: Replace opencoded cpumask_next_wrap() in move_to_next_cpu()

rv: Add opid per-cpu monitor

2025-07-28T20:47:35+00:00

Add a per-cpu monitor as part of the sched model:
* opid: operations with preemption and irq disabled
    Monitor to ensure wakeup and need_resched occur with irq and
    preemption disabled or in irq handlers.

Cc: Jonathan Corbet 
Cc: Masami Hiramatsu 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Tomas Glozar 
Cc: Juri Lelli 
Cc: Clark Williams 
Cc: John Kacur 
Link: https://lore.kernel.org/20250728135022.255578-10-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco 
Acked-by: Nam Cao 
Tested-by: Nam Cao 
Signed-off-by: Steven Rostedt (Google)

rv: Add nrp and sssw per-task monitors

2025-07-28T20:47:34+00:00

Add 2 per-task monitors as part of the sched model:

* nrp: need-resched preempts
    Monitor to ensure preemption requires need resched.
* sssw: set state sleep and wakeup
    Monitor to ensure sched_set_state to sleepable leads to sleeping and
    sleeping tasks require wakeup.

Cc: Ingo Molnar 
Cc: Jonathan Corbet 
Cc: Masami Hiramatsu 
Cc: Tomas Glozar 
Cc: Juri Lelli 
Cc: Clark Williams 
Cc: John Kacur 
Cc: Peter Zijlstra 
Link: https://lore.kernel.org/20250728135022.255578-9-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco 
Acked-by: Nam Cao 
Tested-by: Nam Cao 
Signed-off-by: Steven Rostedt (Google)

rv: Replace tss and sncid monitors with more complete sts

2025-07-28T20:47:34+00:00

The tss monitor currently guarantees task switches can happen only while
scheduling, whereas the sncid monitor enforces scheduling occurs with
interrupt disabled.

Replace the monitors with a more comprehensive specification which
implies both but also ensures that:
* each scheduler call disable interrupts to switch
* each task switch happens with interrupts disabled

Cc: Ingo Molnar 
Cc: Jonathan Corbet 
Cc: Masami Hiramatsu 
Cc: Nam Cao 
Cc: Tomas Glozar 
Cc: Juri Lelli 
Cc: Clark Williams 
Cc: John Kacur 
Cc: Peter Zijlstra 
Link: https://lore.kernel.org/20250728135022.255578-8-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco 
Signed-off-by: Steven Rostedt (Google)

sched: Adapt sched tracepoints for RV task model

2025-07-28T20:47:34+00:00

Add the following tracepoint:
* sched_set_need_resched(tsk, cpu, tif)
    Called when a task is set the need resched [lazy] flag

Remove the unused ip parameter from sched_entry and sched_exit and alter
sched_entry to have a value of preempt consistent with the one used in
sched_switch.

Also adapt all monitors using sched_{entry,exit} to avoid breaking build.

These tracepoints are useful to describe the Linux task model and are
adapted from the patches by Daniel Bristot de Oliveira
(https://bristot.me/linux-task-model/).

Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Masami Hiramatsu 
Cc: Nam Cao 
Cc: Tomas Glozar 
Cc: Juri Lelli 
Cc: Clark Williams 
Cc: John Kacur 
Link: https://lore.kernel.org/20250728135022.255578-7-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco 
Signed-off-by: Steven Rostedt (Google)

rv: Retry when da monitor detects race conditions

2025-07-28T20:47:34+00:00

DA monitor can be accessed from multiple cores simultaneously, this is
likely, for instance when dealing with per-task monitors reacting on
events that do not always occur on the CPU where the task is running.
This can cause race conditions where two events change the next state
and we see inconsistent values. E.g.:

  [62] event_srs: 27: sleepable x sched_wakeup -> running (final)
  [63] event_srs: 27: sleepable x sched_set_state_sleepable -> sleepable
  [63] error_srs: 27: event sched_switch_suspend not expected in the state running

In this case the monitor fails because the event on CPU 62 wins against
the one on CPU 63, although the correct state should have been
sleepable, since the task get suspended.

Detect if the current state was modified by using try_cmpxchg while
storing the next value. If it was, try again reading the current state.
After a maximum number of failed retries, react by calling a special
tracepoint, print on the console and reset the monitor.

Remove the functions da_monitor_curr_state() and da_monitor_set_state()
as they only hide the underlying implementation in this case.

Monitors where this type of condition can occur must be able to account
for racing events in any possible order, as we cannot know the winner.

Cc: Ingo Molnar 
Cc: Masami Hiramatsu 
Cc: Tomas Glozar 
Cc: Juri Lelli 
Cc: Clark Williams 
Cc: John Kacur 
Cc: Peter Zijlstra 
Link: https://lore.kernel.org/20250728135022.255578-6-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco 
Reviewed-by: Nam Cao 
Signed-off-by: Steven Rostedt (Google)

rv: Adjust monitor dependencies

2025-07-28T20:47:34+00:00

RV monitors relying on the preemptirqs tracepoints are set as dependent
on PREEMPT_TRACER and IRQSOFF_TRACER. In fact, those configurations do
enable the tracepoints but are not the minimal configurations enabling
them, which are TRACE_PREEMPT_TOGGLE and TRACE_IRQFLAGS (not selectable
manually).

Set TRACE_PREEMPT_TOGGLE and TRACE_IRQFLAGS as dependencies for
monitors.

Cc: Masami Hiramatsu 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Tomas Glozar 
Cc: Juri Lelli 
Cc: Clark Williams 
Cc: John Kacur 
Link: https://lore.kernel.org/20250728135022.255578-5-gmonaco@redhat.com
Fixes: fbe6c09b7eb4 ("rv: Add scpd, snep and sncid per-cpu monitors")
Acked-by: Nam Cao 
Signed-off-by: Gabriele Monaco 
Signed-off-by: Steven Rostedt (Google)

rv: Use strings in da monitors tracepoints

2025-07-28T20:47:34+00:00

Using DA monitors tracepoints with KASAN enabled triggers the following
warning:

 BUG: KASAN: global-out-of-bounds in do_trace_event_raw_event_event_da_monitor+0xd6/0x1a0
 Read of size 32 at addr ffffffffaada8980 by task ...
 Call Trace:
  
 [...]
  do_trace_event_raw_event_event_da_monitor+0xd6/0x1a0
  ? __pfx_do_trace_event_raw_event_event_da_monitor+0x10/0x10
  ? trace_event_sncid+0x83/0x200
  trace_event_sncid+0x163/0x200
 [...]
 The buggy address belongs to the variable:
  automaton_snep+0x4e0/0x5e0

This is caused by the tracepoints reading 32 bytes __array instead of
__string from the automata definition. Such strings are literals and
reading 32 bytes ends up in out of bound memory accesses (e.g. the next
automaton's data in this case).
The error is harmless as, while printing the string, we stop at the null
terminator, but it should still be fixed.

Use the __string facilities while defining the tracepoints to avoid
reading out of bound memory.

Cc: Masami Hiramatsu 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Tomas Glozar 
Cc: Juri Lelli 
Cc: Clark Williams 
Cc: John Kacur 
Link: https://lore.kernel.org/20250728135022.255578-4-gmonaco@redhat.com
Fixes: 792575348ff7 ("rv/include: Add deterministic automata monitor definition via C macros")
Reviewed-by: Nam Cao 
Signed-off-by: Gabriele Monaco 
Signed-off-by: Steven Rostedt (Google)

rv: Remove trailing whitespace from tracepoint string

2025-07-28T20:47:34+00:00

RV event tracepoints print a line with the format:
    "event_xyz: S0 x event -> S1 "
    "event_xyz: S1 x event -> S0 (final)"

While printing an event leading to a non-final state, the line
has a trailing white space (visible above before the closing ").

Adapt the format string not to print the trailing whitespace if we are
not printing "(final)".

Cc: Masami Hiramatsu 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Tomas Glozar 
Cc: Juri Lelli 
Cc: Clark Williams 
Cc: John Kacur 
Link: https://lore.kernel.org/20250728135022.255578-3-gmonaco@redhat.com
Reviewed-by: Nam Cao 
Signed-off-by: Gabriele Monaco 
Signed-off-by: Steven Rostedt (Google)

rv: Fix wrong type cast in reactors_show() and monitor_reactor_show()

2025-07-28T14:39:34+00:00

Argument 'p' of reactors_show() and monitor_reactor_show() is not a pointer
to struct rv_reactor, it is actually a pointer to the list_head inside
struct rv_reactor. Therefore it's wrong to cast 'p' to struct rv_reactor *.

This wrong type cast has been there since the beginning. But it still
worked because the list_head was the first field in struct rv_reactor_def.
This is no longer true since commit 3d3c376118b5 ("rv: Merge struct
rv_reactor_def into struct rv_reactor") moved the list_head, and this wrong
type cast became a functional problem.

Properly use container_of() instead.

Cc: Masami Hiramatsu 
Cc: Mathieu Desnoyers 
Cc: Gabriele Monaco 
Link: https://lore.kernel.org/b4febbd6844311209e4c8768b65d508b81bd8c9b.1753625621.git.namcao@linutronix.de
Fixes: 3d3c376118b5 ("rv: Merge struct rv_reactor_def into struct rv_reactor")
Signed-off-by: Nam Cao 
Signed-off-by: Steven Rostedt (Google)