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[68.48.65.54]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8f46e27d555sm165184196d6.7.2026.07.07.11.02.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2026 11:02:49 -0700 (PDT) From: Michael Bommarito To: Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers Cc: Beau Belgrave , XIAO WU , Shuah Khan , linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3] selftests/user_events: wait for deferred event teardown after unregister Date: Tue, 7 Jul 2026 14:02:40 -0400 Message-ID: <20260707180240.2887081-1-michael.bommarito@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Unregistering a user event now defers the drop of the enabler's event reference (and the freeing of the enabler) past an RCU grace period. As a result DIAG_IOCSDEL can transiently fail with -EBUSY while that last reference is still being dropped, where it previously succeeded immediately. Two tests assumed the delete takes effect the instant the unregister returns: - abi_test "flags" deletes the event right after disabling it. - perf_test's fixture teardown clear() deletes __test_event before the next test registers the same name; a stale event makes the following registration fail with -EADDRINUSE. Retry the delete until it succeeds (or the event is already gone) with a bounded wait, matching the existing wait_for_delete() idiom in the same suite, so the tests are robust to the deferred teardown. Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Michael Bommarito --- This resends only the selftest patch; the tracing/user_events fix that was patch 1/2 of the v2 series is unchanged and being applied separately. v2 -> v3: - abi_test wait_for_event_delete(): only retry the delete on -EBUSY, treat an already-deleted event (-ENOENT) as success, and return any other error immediately instead of spinning for the full 10s timeout. perf_test's clear() already discriminated on errno this way; the two now match. Reported by Sashiko automated review. .../testing/selftests/user_events/abi_test.c | 29 ++++++++++++++++++- .../testing/selftests/user_events/perf_test.c | 26 +++++++++++++++-- 2 files changed, 51 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/user_events/abi_test.c b/tools/testing/selftests/user_events/abi_test.c index 85892b3b719cc..b71813eaf5c04 100644 --- a/tools/testing/selftests/user_events/abi_test.c +++ b/tools/testing/selftests/user_events/abi_test.c @@ -132,6 +132,33 @@ static int event_delete(void) return ret; } +/* + * Deleting an event drops its last reference, but an unregister may defer + * that put (and the freeing of the associated enabler) past an RCU grace + * period. The delete can therefore transiently fail with -EBUSY while the + * previous reference is still being dropped. Retry only on that transient + * failure; treat an already-deleted event (-ENOENT) as success and return + * any other error immediately rather than spinning for the full timeout. + */ +static int wait_for_event_delete(void) +{ + int i, ret; + + for (i = 0; i < 10000; ++i) { + ret = event_delete(); + + if (ret == 0 || errno == ENOENT) + return 0; + + if (errno != EBUSY) + return ret; + + usleep(1000); + } + + return ret; +} + static int reg_enable_multi(void *enable, int size, int bit, int flags, char *args) { @@ -262,7 +289,7 @@ TEST_F(user, flags) { ASSERT_TRUE(event_exists()); /* Ensure we can delete it */ - ASSERT_EQ(0, event_delete()); + ASSERT_EQ(0, wait_for_event_delete()); /* USER_EVENT_REG_MAX or above is not allowed */ ASSERT_EQ(-1, reg_enable_flags(&self->check, sizeof(int), 0, diff --git a/tools/testing/selftests/user_events/perf_test.c b/tools/testing/selftests/user_events/perf_test.c index cafec0e52eb31..5727cb5b914cf 100644 --- a/tools/testing/selftests/user_events/perf_test.c +++ b/tools/testing/selftests/user_events/perf_test.c @@ -85,6 +85,7 @@ static int get_offset(void) static int clear(int *check) { struct user_unreg unreg = {0}; + int i, ret; unreg.size = sizeof(unreg); unreg.disable_bit = 31; @@ -99,13 +100,32 @@ static int clear(int *check) if (errno != ENOENT) return -1; - if (ioctl(fd, DIAG_IOCSDEL, "__test_event") == -1) - if (errno != ENOENT) + /* + * Deleting the event drops its last reference, but the unregister + * above defers that put (and the freeing of the enabler) past an RCU + * grace period. The delete can therefore transiently fail with -EBUSY + * until that reference is dropped. Retry for up to ~10 seconds so the + * event is actually gone before the next test registers the same name. + */ + for (i = 0; i < 10000; ++i) { + ret = ioctl(fd, DIAG_IOCSDEL, "__test_event"); + + if (ret == 0 || errno == ENOENT) { + ret = 0; + break; + } + + if (errno != EBUSY) { + close(fd); return -1; + } + + usleep(1000); + } close(fd); - return 0; + return ret; } FIXTURE(user) { -- 2.53.0