On Fri, Feb 23, 2024 at 12:56:34PM -0500, Steven Rostedt wrote:

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

[
   This is a treewide change. I will likely re-create this patch again in
   the second week of the merge window of v6.9 and submit it then. Hoping
   to keep the conflicts that it will cause to a minimum.
]

With the rework of how the __string() handles dynamic strings where it
saves off the source string in field in the helper structure[1], the
assignment of that value to the trace event field is stored in the helper
value and does not need to be passed in again.

This means that with:

  __string(field, mystring)

Which use to be assigned with __assign_str(field, mystring), no longer
needs the second parameter and it is unused. With this, __assign_str()
will now only get a single parameter.

There's over 700 users of __assign_str() and because coccinelle does not
handle the TRACE_EVENT() macro I ended up using the following sed script:

  git grep -l __assign_str | while read a ; do
      sed -e 's/\(__assign_str([^,]*[^ ,]\) *,[^;]*/\1)/' $a > /tmp/test-file;
      mv /tmp/test-file $a;
  done

I then searched for __assign_str() that did not end with ';' as those
were multi line assignments that the sed script above would fail to catch.

Note, the same updates will need to be done for:

  __assign_str_len()
  __assign_rel_str()
  __assign_rel_str_len()
  __assign_bitmask()
  __assign_rel_bitmask()
  __assign_cpumask()
  __assign_rel_cpumask()

[1] https://lore.kernel.org/linux-trace-kernel/20240222211442.634192653@goodmis.org/ (local)

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 arch/arm64/kernel/trace-events-emulation.h    |   2 +-
 arch/powerpc/include/asm/trace.h              |   4 +-
 arch/x86/kvm/trace.h                          |   2 +-
 drivers/base/regmap/trace.h                   |  18 +--
 drivers/base/trace.h                          |   2 +-
 drivers/block/rnbd/rnbd-srv-trace.h           |  12 +-
 drivers/cxl/core/trace.h                      |  24 ++--

snip to CXL

snip to poison

I think I get that the above changes work because the TP_STRUCT__entry for
these did:
	__string(memdev, dev_name(&cxlmd->dev))
	__string(host, dev_name(cxlmd->dev.parent))

For the above 2, there was no helper in TP_STRUCT__entry. A recently
posted patch is fixing that up to be __string(region, NULL) See [1],
with the actual assignment still happening in TP_fast_assign.

Does that assign logic need to move to the TP_STRUCT__entry definition
when you merge these changes? I'm not clear how much logic is able to be
included, ie like 'C' style code in the TP_STRUCT__entry.

[1]
https://lore.kernel.org/linux-cxl/20240314044301.2108650-1-alison.schofield@intel.com/ (local)

Thanks for helping,
Alison

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