Main user visible change:
- User events can now have "multi formats"
The current user events have a single format. If another event is created
with a different format, it will fail to be created. That is, once an
event name is used, it cannot be used again with a different format. This
can cause issues if a library is using an event and updates its format.
An application using the older format will prevent an application using
the new library from registering its event.
A task could also DOS another application if it knows the event names, and
it creates events with different formats.
The multi-format event is in a different name space from the single
format. Both the event name and its format are the unique identifier.
This will allow two different applications to use the same user event name
but with different payloads.
- Added support to have ftrace_dump_on_oops dump out instances and
not just the main top level tracing buffer.
Other changes:
- Add eventfs_root_inode
Only the root inode has a dentry that is static (never goes away) and
stores it upon creation. There's no reason that the thousands of other
eventfs inodes should have a pointer that never gets set in its
descriptor. Create a eventfs_root_inode desciptor that has a eventfs_inode
descriptor and a dentry pointer, and only the root inode will use this.
- Added WARN_ON()s in eventfs
There's some conditionals remaining in eventfs that should never be hit,
but instead of removing them, add WARN_ON() around them to make sure that
they are never hit.
- Have saved_cmdlines allocation also include the map_cmdline_to_pid array
The saved_cmdlines structure allocates a large amount of data to hold its
mappings. Within it, it has three arrays. Two are already apart of it:
map_pid_to_cmdline[] and saved_cmdlines[]. More memory can be saved by
also including the map_cmdline_to_pid[] array as well.
- Restructure __string() and __assign_str() macros used in TRACE_EVENT().
Dynamic strings in TRACE_EVENT() are declared with:
__string(name, source)
And assigned with:
__assign_str(name, source)
In the tracepoint callback of the event, the __string() is used to get the
size needed to allocate on the ring buffer and __assign_str() is used to
copy the string into the ring buffer. There's a helper structure that is
created in the TRACE_EVENT() macro logic that will hold the string length
and its position in the ring buffer which is created by __string().
There are several trace events that have a function to create the string
to save. This function is executed twice. Once for __string() and again
for __assign_str(). There's no reason for this. The helper structure could
also save the string it used in __string() and simply copy that into
__assign_str() (it also already has its length).
By using the structure to store the source string for the assignment, it
means that the second argument to __assign_str() is no longer needed.
It will be removed in the next merge window, but for now add a warning if
the source string given to __string() is different than the source string
given to __assign_str(), as the source to __assign_str() isn't even used
and will be going away.
- Added checks to make sure that the source of __string() is also the
source of __assign_str() so that it can be safely removed in the next
merge window.
Included fixes that the above check found.
- Other minor clean ups and fixes
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Merge tag 'trace-v6.9-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing updates from Steven Rostedt:
"Main user visible change:
- User events can now have "multi formats"
The current user events have a single format. If another event is
created with a different format, it will fail to be created. That
is, once an event name is used, it cannot be used again with a
different format. This can cause issues if a library is using an
event and updates its format. An application using the older format
will prevent an application using the new library from registering
its event.
A task could also DOS another application if it knows the event
names, and it creates events with different formats.
The multi-format event is in a different name space from the single
format. Both the event name and its format are the unique
identifier. This will allow two different applications to use the
same user event name but with different payloads.
- Added support to have ftrace_dump_on_oops dump out instances and
not just the main top level tracing buffer.
Other changes:
- Add eventfs_root_inode
Only the root inode has a dentry that is static (never goes away)
and stores it upon creation. There's no reason that the thousands
of other eventfs inodes should have a pointer that never gets set
in its descriptor. Create a eventfs_root_inode desciptor that has a
eventfs_inode descriptor and a dentry pointer, and only the root
inode will use this.
- Added WARN_ON()s in eventfs
There's some conditionals remaining in eventfs that should never be
hit, but instead of removing them, add WARN_ON() around them to
make sure that they are never hit.
- Have saved_cmdlines allocation also include the map_cmdline_to_pid
array
The saved_cmdlines structure allocates a large amount of data to
hold its mappings. Within it, it has three arrays. Two are already
apart of it: map_pid_to_cmdline[] and saved_cmdlines[]. More memory
can be saved by also including the map_cmdline_to_pid[] array as
well.
- Restructure __string() and __assign_str() macros used in
TRACE_EVENT()
Dynamic strings in TRACE_EVENT() are declared with:
__string(name, source)
And assigned with:
__assign_str(name, source)
In the tracepoint callback of the event, the __string() is used to
get the size needed to allocate on the ring buffer and
__assign_str() is used to copy the string into the ring buffer.
There's a helper structure that is created in the TRACE_EVENT()
macro logic that will hold the string length and its position in
the ring buffer which is created by __string().
There are several trace events that have a function to create the
string to save. This function is executed twice. Once for
__string() and again for __assign_str(). There's no reason for
this. The helper structure could also save the string it used in
__string() and simply copy that into __assign_str() (it also
already has its length).
By using the structure to store the source string for the
assignment, it means that the second argument to __assign_str() is
no longer needed.
It will be removed in the next merge window, but for now add a
warning if the source string given to __string() is different than
the source string given to __assign_str(), as the source to
__assign_str() isn't even used and will be going away.
- Added checks to make sure that the source of __string() is also the
source of __assign_str() so that it can be safely removed in the
next merge window.
Included fixes that the above check found.
- Other minor clean ups and fixes"
* tag 'trace-v6.9-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (34 commits)
tracing: Add __string_src() helper to help compilers not to get confused
tracing: Use strcmp() in __assign_str() WARN_ON() check
tracepoints: Use WARN() and not WARN_ON() for warnings
tracing: Use div64_u64() instead of do_div()
tracing: Support to dump instance traces by ftrace_dump_on_oops
tracing: Remove second parameter to __assign_rel_str()
tracing: Add warning if string in __assign_str() does not match __string()
tracing: Add __string_len() example
tracing: Remove __assign_str_len()
ftrace: Fix most kernel-doc warnings
tracing: Decrement the snapshot if the snapshot trigger fails to register
tracing: Fix snapshot counter going between two tracers that use it
tracing: Use EVENT_NULL_STR macro instead of open coding "(null)"
tracing: Use ? : shortcut in trace macros
tracing: Do not calculate strlen() twice for __string() fields
tracing: Rework __assign_str() and __string() to not duplicate getting the string
cxl/trace: Properly initialize cxl_poison region name
net: hns3: tracing: fix hclgevf trace event strings
drm/i915: Add missing ; to __assign_str() macros in tracepoint code
NFSD: Fix nfsd_clid_class use of __string_len() macro
...
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