On 18/07/2023 12:24, David Hildenbrand wrote:
> On 18.07.23 13:23, David Hildenbrand wrote:
>> On 18.07.23 12:49, Ryan Roberts wrote:
>>> On 17/07/2023 18:40, David Hildenbrand wrote:
>>>> On 17.07.23 12:31, Ryan Roberts wrote:
>>>>> The `migration` test currently has a number of robustness problems that
>>>>> cause it to hang and leak resources.
>>>>>
>>>>> Timeout: There are 3 tests, which each previously ran for 60 seconds.
>>>>> However, the timeout in mm/settings for a single test binary was set to
>>>>> 45 seconds. So when run using run_kselftest.sh, the top level timeout
>>>>> would trigger before the test binary was finished. Solve this by meeting
>>>>> in the middle; each of the 3 tests now runs for 20 seconds (for a total
>>>>> of 60), and the top level timeout is set to 90 seconds.
>>>>>
>>>>> Leaking child processes: the `shared_anon` test fork()s some children
>>>>> but then an ASSERT() fires before the test kills those children. The
>>>>> assert causes immediate exit of the parent and leaking of the children.
>>>>> Furthermore, if run using the run_kselftest.sh wrapper, the wrapper
>>>>> would get stuck waiting for those children to exit, which never happens.
>>>>> Solve this by deferring any asserts until after the children are killed.
>>>>> The same pattern is used for the threaded tests for uniformity.
>>>>>
>>>>> With these changes, the test binary now runs to completion on arm64,
>>>>> with 2 tests passing and the `shared_anon` test failing.
>>>>>
>>>>> Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
>>>>> ---
>>>>> tools/testing/selftests/mm/migration.c | 14 ++++++++++----
>>>>> tools/testing/selftests/mm/settings | 2 +-
>>>>> 2 files changed, 11 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/tools/testing/selftests/mm/migration.c
>>>>> b/tools/testing/selftests/mm/migration.c
>>>>> index 379581567f27..189d7d9070e8 100644
>>>>> --- a/tools/testing/selftests/mm/migration.c
>>>>> +++ b/tools/testing/selftests/mm/migration.c
>>>>> @@ -15,7 +15,7 @@
>>>>> #include <time.h>
>>>>> #define TWOMEG (2<<20)
>>>>> -#define RUNTIME (60)
>>>>> +#define RUNTIME (20)
>>>>> #define ALIGN(x, a) (((x) + (a - 1)) & (~((a) - 1)))
>>>>> @@ -118,6 +118,7 @@ TEST_F_TIMEOUT(migration, private_anon, 2*RUNTIME)
>>>>> {
>>>>> uint64_t *ptr;
>>>>> int i;
>>>>> + int ret;
>>>>> if (self->nthreads < 2 || self->n1 < 0 || self->n2 < 0)
>>>>> SKIP(return, "Not enough threads or NUMA nodes available");
>>>>> @@ -131,9 +132,10 @@ TEST_F_TIMEOUT(migration, private_anon, 2*RUNTIME)
>>>>> if (pthread_create(&self->threads[i], NULL, access_mem, ptr))
>>>>> perror("Couldn't create thread");
>>>>> - ASSERT_EQ(migrate(ptr, self->n1, self->n2), 0);
>>>>> + ret = migrate(ptr, self->n1, self->n2);
>>>>> for (i = 0; i < self->nthreads - 1; i++)
>>>>> ASSERT_EQ(pthread_cancel(self->threads[i]), 0);
>>>>> + ASSERT_EQ(ret, 0);
>>>>
>>>> Why is that required? This does not involve fork.
>>>
>>> It's not required. I was just trying to keep everything aligned to the same
>>> pattern.
>>>
>>>>
>>>>> }
>>>>> /*
>>>>> @@ -144,6 +146,7 @@ TEST_F_TIMEOUT(migration, shared_anon, 2*RUNTIME)
>>>>> pid_t pid;
>>>>> uint64_t *ptr;
>>>>> int i;
>>>>> + int ret;
>>>>> if (self->nthreads < 2 || self->n1 < 0 || self->n2 < 0)
>>>>> SKIP(return, "Not enough threads or NUMA nodes available");
>>>>> @@ -161,9 +164,10 @@ TEST_F_TIMEOUT(migration, shared_anon, 2*RUNTIME)
>>>>> self->pids[i] = pid;
>>>>> }
>>>>> - ASSERT_EQ(migrate(ptr, self->n1, self->n2), 0);
>>>>> + ret = migrate(ptr, self->n1, self->n2);
>>>>> for (i = 0; i < self->nthreads - 1; i++)
>>>>> ASSERT_EQ(kill(self->pids[i], SIGTERM), 0);
>>>>> + ASSERT_EQ(ret, 0);
>>>>
>>>>
>>>> Might be cleaner to also:
>>>
>>> Or instead of? I agree this is neater, so will undo the moving of the ASSERT()
>>> and rely on this prctl.
>>
>> I was thinking about possible races when our parent process already
>> quits before our child managed to set the prctl. prctl() won't do
>> anything in that case, hmmmm.
>>
>> But similarly, existing code might already trigger the migrate() + kill
>> before the child processes even started to access_mem().
>>
>> Racy :)
>>
>
> Maybe what would work, is checking after the prctl() in the child if the parent
> is already gone.
Like this?
if (!pid) {
prctl(PR_SET_PDEATHSIG, SIGHUP);
/* Parent may have died before prctl so check now. */
if (getppid() == 1)
kill(getpid(), SIGHUP);
access_mem(ptr);
}
>
