mirror of
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d6f38c1239
- 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
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Merge tag 'trace-v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
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()
|
||
|---|---|---|
| .. | ||
| coresight | ||
| postprocess | ||
| rv | ||
| boottime-trace.rst | ||
| debugging.rst | ||
| eprobetrace.rst | ||
| events-kmem.rst | ||
| events-msr.rst | ||
| events-nmi.rst | ||
| events-power.rst | ||
| events.rst | ||
| fprobe.rst | ||
| fprobetrace.rst | ||
| ftrace-design.rst | ||
| ftrace-uses.rst | ||
| ftrace.rst | ||
| function-graph-fold.vim | ||
| hisi-ptt.rst | ||
| histogram-design.rst | ||
| histogram.rst | ||
| hwlat_detector.rst | ||
| index.rst | ||
| intel_th.rst | ||
| kprobes.rst | ||
| kprobetrace.rst | ||
| mmiotrace.rst | ||
| osnoise-tracer.rst | ||
| ring-buffer-design.rst | ||
| ring-buffer-map.rst | ||
| stm.rst | ||
| sys-t.rst | ||
| timerlat-tracer.rst | ||
| tracepoint-analysis.rst | ||
| tracepoints.rst | ||
| uprobetracer.rst | ||
| user_events.rst | ||