linux-stable.git/kernel/trace/trace_hwlat.c, branch v5.16.2

tracing/hwlat: Make some internal symbols static

2021-10-26T13:18:28+00:00

The sparse tool complains as follows:

kernel/trace/trace_hwlat.c:82:27: warning: symbol 'hwlat_single_cpu_data' was not declared. Should it be static?
kernel/trace/trace_hwlat.c:83:1: warning: symbol '__pcpu_scope_hwlat_per_cpu_data' was not declared. Should it be static?

This symbol is not used outside of trace_hwlat.c, so this commit
marks it static.

Link: https://lkml.kernel.org/r/20211021035225.1050685-1-bobo.shaobowang@huawei.com

Signed-off-by: Wang ShaoBo 
Signed-off-by: Steven Rostedt (VMware)

tracing: Disable "other" permission bits in the tracefs files

2021-10-08T22:08:43+00:00

When building the files in the tracefs file system, do not by default set
any permissions for OTH (other). This will make it easier for admins who
want to define a group for accessing tracefs and not having to first
disable all the permission bits for "other" in the file system.

As tracing can leak sensitive information, it should never by default
allowing all users access. An admin can still set the permission bits for
others to have access, which may be useful for creating a honeypot and
seeing who takes advantage of it and roots the machine.

Link: https://lkml.kernel.org/r/20210818153038.864149276@goodmis.org

Signed-off-by: Steven Rostedt (VMware)

tracing: Replace deprecated CPU-hotplug functions.

2021-08-17T19:47:14+00:00

The functions get_online_cpus() and put_online_cpus() have been
deprecated during the CPU hotplug rework. They map directly to
cpus_read_lock() and cpus_read_unlock().

Replace deprecated CPU-hotplug functions with the official version.
The behavior remains unchanged.

Link: https://lkml.kernel.org/r/20210803141621.780504-37-bigeasy@linutronix.de

Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Acked-by: Daniel Bristot de Oliveira 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Steven Rostedt (VMware)

tracing: Quiet smp_processor_id() use in preemptable warning in hwlat

2021-08-05T13:27:31+00:00

The hardware latency detector (hwlat) has a mode that it runs one thread
across CPUs. The logic to move from the currently running CPU to the next
one in the list does a smp_processor_id() to find where it currently is.
Unfortunately, it's done with preemption enabled, and this triggers a
warning for using smp_processor_id() in a preempt enabled section.

As it is only using smp_processor_id() to get information on where it
currently is in order to simply move it to the next CPU, it doesn't really
care if it got moved in the mean time. It will simply balance out later if
such a case arises.

Switch smp_processor_id() to raw_smp_processor_id() to quiet that warning.

Link: https://lkml.kernel.org/r/20210804141848.79edadc0@oasis.local.home

Acked-by: Daniel Bristot de Oliveira 
Fixes: 8fa826b7344d ("trace/hwlat: Implement the mode config option")
Signed-off-by: Steven Rostedt (VMware)

trace/hwlat: Support hotplug operations

2021-06-25T23:57:24+00:00

Enable and disable hwlat thread during cpu hotplug online
and offline operations, respectivelly.

Link: https://lore.kernel.org/linux-doc/20210621134636.5b332226@oasis.local.home/
Link: https://lkml.kernel.org/r/52012d25ea35491a0f8088b947864d8df8e25157.1624372313.git.bristot@redhat.com

Cc: Phil Auld 
Cc: Sebastian Andrzej Siewior 
Cc: Kate Carcia 
Cc: Jonathan Corbet 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Alexandre Chartre 
Cc: Clark Willaims 
Cc: John Kacur 
Cc: Juri Lelli 
Cc: Borislav Petkov 
Cc: "H. Peter Anvin" 
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Suggested-by: Steven Rostedt (VMware) 
Signed-off-by: Daniel Bristot de Oliveira 
Signed-off-by: Steven Rostedt (VMware)

trace/hwlat: Protect kdata->kthread with get/put_online_cpus

2021-06-25T23:57:24+00:00

In preparation to the hotplug support, protect kdata->kthread
with get/put_online_cpus() to avoid concurrency with hotplug
operations.

Link: https://lore.kernel.org/linux-doc/20210621134636.5b332226@oasis.local.home/
Link: https://lkml.kernel.org/r/8bdb2a56f46abfd301d6fffbf43448380c09a6f5.1624372313.git.bristot@redhat.com

Cc: Phil Auld 
Cc: Sebastian Andrzej Siewior 
Cc: Kate Carcia 
Cc: Jonathan Corbet 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Alexandre Chartre 
Cc: Clark Willaims 
Cc: John Kacur 
Cc: Juri Lelli 
Cc: Borislav Petkov 
Cc: "H. Peter Anvin" 
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Suggested-by: Steven Rostedt (VMware) 
Signed-off-by: Daniel Bristot de Oliveira 
Signed-off-by: Steven Rostedt (VMware)

trace/hwlat: Remove printk from sampling loop

2021-06-25T22:26:12+00:00

hwlat has some time operation checks on the sample loop, and it is
currently using pr_err (printk) to report them. The problem is that
this can lead the system to an unresponsible state due to an overflow of
printk messages. This problem can be mitigated by writing the error
message to the trace buffer.

Remove the printk messages from the sampling loop, switching the to
messages in the trace buffer.

No functional change.

Link: https://lkml.kernel.org/r/9d77c34869748aa105e965c769d24642914eea3a.1624372313.git.bristot@redhat.com

Cc: Phil Auld 
Cc: Sebastian Andrzej Siewior 
Cc: Kate Carcia 
Cc: Jonathan Corbet 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Alexandre Chartre 
Cc: Clark Willaims 
Cc: John Kacur 
Cc: Juri Lelli 
Cc: Borislav Petkov 
Cc: "H. Peter Anvin" 
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira 
Signed-off-by: Steven Rostedt (VMware)

trace/hwlat: Use trace_min_max_param for width and window params

2021-06-25T22:26:12+00:00

Use the trace_min_max_param to reduce code duplication.

No functional change.

Link: https://lkml.kernel.org/r/b91accd5a7c6c14ea02d3379aae974ba22b47dd6.1624372313.git.bristot@redhat.com

Cc: Phil Auld 
Cc: Sebastian Andrzej Siewior 
Cc: Kate Carcia 
Cc: Jonathan Corbet 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Alexandre Chartre 
Cc: Clark Willaims 
Cc: John Kacur 
Cc: Juri Lelli 
Cc: Borislav Petkov 
Cc: "H. Peter Anvin" 
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira 
Signed-off-by: Steven Rostedt (VMware)

trace/hwlat: Implement the per-cpu mode

2021-06-25T22:23:22+00:00

Implements the per-cpu mode in which a sampling thread is created for
each cpu in the "cpus" (and tracing_mask).

The per-cpu mode has the potention to speed up the hwlat detection by
running on multiple CPUs at the same time, at the cost of higher cpu
usage with irqs disabled. Use with care.

[
  Changed get_cpu_data() to static.
  Reported-by: kernel test robot 
]

Link: https://lkml.kernel.org/r/ec06d0ab340e8460d293772faba19ad8a5c371aa.1624372313.git.bristot@redhat.com

Cc: Phil Auld 
Cc: Sebastian Andrzej Siewior 
Cc: Kate Carcia 
Cc: Jonathan Corbet 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Alexandre Chartre 
Cc: Clark Willaims 
Cc: John Kacur 
Cc: Juri Lelli 
Cc: Borislav Petkov 
Cc: "H. Peter Anvin" 
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira 
Signed-off-by: Steven Rostedt (VMware)

trace/hwlat: Switch disable_migrate to mode none

2021-06-24T19:37:56+00:00

When in the round-robin mode, if the tracer detects a change in the
hwlatd thread affinity by an external tool, e.g., taskset, the
round-robin logic is disabled. The disable_migrate variable currently
tracks this.

With the addition of the "mode" config and the mode "none," the
disable_migrate logic is equivalent to switch to the "none" mode.

Hence, instead of using a hidden variable to track this behavior,
switch the mode to none, informing the user about this change.

Link: https://lkml.kernel.org/r/a679af672458d6b1f62252605905c5214030f247.1624372313.git.bristot@redhat.com

Cc: Phil Auld 
Cc: Sebastian Andrzej Siewior 
Cc: Kate Carcia 
Cc: Jonathan Corbet 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Alexandre Chartre 
Cc: Clark Willaims 
Cc: John Kacur 
Cc: Juri Lelli 
Cc: Borislav Petkov 
Cc: "H. Peter Anvin" 
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira 
Signed-off-by: Steven Rostedt (VMware)