RE: [PATCH v12 6/7] eal: add unit tests for atomic bit access functions

["Morten Brørup" <mb@smartsharesystems.com>]

> From: David Marchand [mailto:david.marchand@redhat.com]
> Sent: Thursday, 10 October 2024 12.45
> 
> On Fri, Sep 20, 2024 at 12:57 PM Mattias Rönnblom
> <mattias.ronnblom@ericsson.com> wrote:
> > +       static int
> \
> > +       run_parallel_test_and_modify ## size(void *arg)         \
> > +       {
> \
> > +               struct parallel_test_and_set_lcore ## size *lcore =
> arg; \
> > +               uint64_t deadline = rte_get_timer_cycles() +
> \
> > +                       PARALLEL_TEST_RUNTIME * rte_get_timer_hz();
> \
> > +               do {
> \
> > +                       bool old_value;
> \
> > +                       bool new_value = rte_rand() & 1;
> \
> > +                       bool use_assign = rte_rand() & 1;
> \
> > +
> \
> > +                       if (use_assign)
> \
> > +                               old_value =
> rte_bit_atomic_test_and_assign( \
> > +                                       lcore->word, lcore->bit,
> new_value, \
> > +                                       rte_memory_order_relaxed);
> \
> > +                       else
> \
> > +                               old_value = new_value ?
> \
> > +                                       rte_bit_atomic_test_and_set(
> \
> > +                                               lcore->word, lcore-
> >bit, \
> > +
> rte_memory_order_relaxed) : \
> > +
> rte_bit_atomic_test_and_clear(  \
> > +                                               lcore->word, lcore-
> >bit, \
> > +
> rte_memory_order_relaxed); \
> > +                       if (old_value != new_value)
> \
> > +                               lcore->flips++;
> \
> > +               } while (rte_get_timer_cycles() < deadline);
> \
> > +
> \
> > +               return 0;
> \
> > +       }
> \
> > +
> \
> > +       static int
> \
> > +       test_bit_atomic_parallel_test_and_modify ## size(void)
> \
> > +       {
> \
> > +               unsigned int worker_lcore_id;
> \
> > +               uint ## size ## _t word = 0;
> \
> > +               unsigned int bit = rte_rand_max(size);
> \
> > +               struct parallel_test_and_set_lcore ## size lmain = {
> \
> > +                       .word = &word,
> \
> > +                       .bit = bit
> \
> > +               };
> \
> > +               struct parallel_test_and_set_lcore ## size lworker =
> {  \
> > +                       .word = &word,
> \
> > +                       .bit = bit
> \
> > +               };
> \
> > +
> \
> > +               if (rte_lcore_count() < 2) {
> \
> > +                       printf("Need multiple cores to run parallel
> test.\n"); \
> > +                       return TEST_SKIPPED;
> \
> > +               }
> \
> > +
> \
> > +               worker_lcore_id = rte_get_next_lcore(-1, 1, 0);
> \
> > +
> \
> > +               int rc =
> rte_eal_remote_launch(run_parallel_test_and_modify ## size, \
> > +                                              &lworker,
> worker_lcore_id); \
> > +               TEST_ASSERT(rc == 0, "Worker thread launch failed");
> \
> > +
> \
> > +               run_parallel_test_and_modify ## size(&lmain);
> \
> > +
> \
> > +               rte_eal_mp_wait_lcore();
> \
> > +
> \
> > +               uint64_t total_flips = lmain.flips + lworker.flips;
> \
> > +               bool expected_value = total_flips % 2;
> \
> > +
> \
> > +               TEST_ASSERT(expected_value == rte_bit_test(&word,
> bit), \
> > +                           "After %"PRId64" flips, the bit value "
> \
> > +                           "should be %d", total_flips,
> expected_value); \
> > +
> \
> > +               uint64_t expected_word = 0;
> \
> > +               rte_bit_assign(&expected_word, bit, expected_value);
> \
> > +
> \
> > +               TEST_ASSERT(expected_word == word, "Untouched bits
> have " \
> > +                           "changed value");
> \
> > +
> \
> > +               return TEST_SUCCESS;
> \
> > +       }
> > +
> > +GEN_TEST_BIT_PARALLEL_TEST_AND_MODIFY(32)
> > +GEN_TEST_BIT_PARALLEL_TEST_AND_MODIFY(64)
> 
> It appears this test failed once in the CI for an unrelated series
> (uAPI kernel header import):
> https://lab.dpdk.org/results/dashboard/testruns/logs/1385993/
> 
>  + TestCase [ 0] : test_bit_access32 succeeded
>  + TestCase [ 1] : test_bit_access64 succeeded
>  + TestCase [ 2] : test_bit_access32 succeeded
>  + TestCase [ 3] : test_bit_access64 succeeded
>  + TestCase [ 4] : test_bit_v_access32 succeeded
>  + TestCase [ 5] : test_bit_v_access64 succeeded
>  + TestCase [ 6] : test_bit_atomic_access32 succeeded
>  + TestCase [ 7] : test_bit_atomic_access64 succeeded
>  + TestCase [ 8] : test_bit_atomic_v_access32 succeeded
>  + TestCase [ 9] : test_bit_atomic_v_access64 succeeded
>  + TestCase [10] : test_bit_atomic_parallel_assign32 succeeded
>  + TestCase [11] : test_bit_atomic_parallel_assign64 succeeded
>  + TestCase [12] : test_bit_atomic_parallel_test_and_modify32 failed
>  + TestCase [13] : test_bit_atomic_parallel_test_and_modify64 succeeded
>  + TestCase [14] : test_bit_atomic_parallel_flip32 succeeded
>  + TestCase [15] : test_bit_atomic_parallel_flip64 succeeded
>  + TestCase [16] : test_bit_relaxed_set succeeded
>  + TestCase [17] : test_bit_relaxed_clear succeeded
>  + TestCase [18] : test_bit_relaxed_test_set_clear succeeded
> 
> EAL: Test assert test_bit_atomic_parallel_test_and_modify32 line 236
> failed: After 1070523 flips, the bit value should be 1
> 
> Please have a look.

The Coverity report [1] just gave me an idea:

worker_lcore_id = rte_get_next_lcore(-1, 1, 0);
+ TEST_ASSERT(worker_lcore_id < RTE_MAX_LCORE, "Worker thread allocation failed");

Or even better:
Improve rte_eal_remote_launch() by checking the validity of the worker_id parameter.

[1]: https://scan4.scan.coverity.com/#/project-view/60887/10075?selectedIssue=445384