linux-toradex.git/lib/tests/errseq_kunit.c, branch master Linux kernel for Apalis and Colibri modules lib/tests: add KUnit tests for errseq 2026-10-07T02:02:58+00:00 Thomas Maarseveen maarseveent@gmail.com 2026-08-12T18:55:33+00:00 a4747846dfa6f09080d2252d9d442e7dbe333fb2 The errseq_t infrastructure (lib/errseq.c) underpins writeback error reporting but has no regression tests. Its semantics are subtle enough to have needed fixing before: commit b4678df184b3 ("errseq: Always report a writeback error once") changed how unseen errors reach new samplers. Add a KUnit suite covering the documented single-threaded semantics: - a zeroed errseq_t is the "no error yet" epoch - errors are recorded, overwrite one another, and both ends of the valid errno range round-trip exactly - an error nobody has seen samples as zero, so a check against a fresh sample still reports it - errseq_check_and_advance() reports a given error exactly once per cursor and leaves the cursor in place when nothing has changed - once an error has been seen, a fresh sample is current and a check against it reports nothing - the same error recorded again after being seen is reported again, even to a cursor that consumed the first occurrence while another cursor marked the repeat as seen - independent cursors each observe each error The lockless behaviour of errseq_t under concurrent updates and the WARN path for invalid error values are deliberately out of scope. Tested with ./tools/testing/kunit/kunit.py run, with a kunitconfig enabling CONFIG_KUNIT=y and CONFIG_ERRSEQ_KUNIT_TEST=y; all 13 tests pass under ARCH=um. Link: https://lore.kernel.org/20260812-errseq-kunit-v1-1-312be4c3aa0d@gmail.com Signed-off-by: Thomas Maarseveen <maarseveent@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Jeff Layton <jlayton@kernel.org> Cc: David Gow <david@davidgow.net> 
The errseq_t infrastructure (lib/errseq.c) underpins writeback error
reporting but has no regression tests.  Its semantics are subtle enough to
have needed fixing before: commit b4678df184b3 ("errseq: Always report a
writeback error once") changed how unseen errors reach new samplers.

Add a KUnit suite covering the documented single-threaded semantics:

 - a zeroed errseq_t is the "no error yet" epoch
 - errors are recorded, overwrite one another, and both ends of the
   valid errno range round-trip exactly
 - an error nobody has seen samples as zero, so a check against a
   fresh sample still reports it
 - errseq_check_and_advance() reports a given error exactly once per
   cursor and leaves the cursor in place when nothing has changed
 - once an error has been seen, a fresh sample is current and a check
   against it reports nothing
 - the same error recorded again after being seen is reported again,
   even to a cursor that consumed the first occurrence while another
   cursor marked the repeat as seen
 - independent cursors each observe each error

The lockless behaviour of errseq_t under concurrent updates and the WARN
path for invalid error values are deliberately out of scope.

Tested with ./tools/testing/kunit/kunit.py run, with a kunitconfig
enabling CONFIG_KUNIT=y and CONFIG_ERRSEQ_KUNIT_TEST=y; all 13 tests pass
under ARCH=um.

Link: https://lore.kernel.org/20260812-errseq-kunit-v1-1-312be4c3aa0d@gmail.com
Signed-off-by: Thomas Maarseveen <maarseveent@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Jeff Layton <jlayton@kernel.org>
Cc: David Gow <david@davidgow.net>