[PATCH v2 0/2] tracing/user_events: Share tracing state between existing threads

[Jeff Barnes <jeffbarnes@linux.microsoft.com>]

Hi,

This series fixes user_events registration from threads that already share
an address space before the first user_events registration.

The first patch adds regression coverage. The second ensures that
pre-existing threads sharing the same mm_struct also share the same
user_event_mm instead of independently creating wrappers with separate
enabler lists.

With the fix, a second registration using the same enable address and bit
is correctly rejected with EADDRINUSE.

The series was rebased onto Linux 7.3-rc6. The complete user_events ABI
selftest suite passes under virtme-ng:

PASSED: 7 / 7 tests passed.
Totals: pass:7 fail:0 xfail:0 xpass:0 skip:0 error:0
Changes in v2:

- Remove the unreachable second-registration cleanup assertion reported by
  Sashiko. ASSERT_EQ(-1, registration.second_ret) aborts on mismatch, so
  the subsequent if (!registration.second_ret) condition could never
  execute.
- Remove the now-unused second_unreg_ret field while retaining cleanup
  when the second registration unexpectedly succeeds.
- Remove the redundant first-registration cleanup guard.
- Use the natural alignment of the __u32 enable word and correct
  continuation indentation.
- Rebase onto Linux 7.3-rc6.

Both patches pass scripts/checkpatch.pl --strict with 0 errors,
0 warnings, and 0 checks.

Jeff

Jeff Barnes (2):
  selftests/user_events: Test registration from existing threads
  tracing/user_events: Share tracing state between existing threads


 kernel/trace/trace_events_user.c              |  78 +++++++++--
 .../testing/selftests/user_events/abi_test.c  | 125 ++++++++++++++++++
 2 files changed, 189 insertions(+), 14 deletions(-)

-- 
2.43.0