> diff --git
> a/tools/testing/selftests/net/bench/page_pool/bench_page_pool_simple.c
> b/tools/testing/selftests/net/bench/page_pool/bench_page_pool_simple.c
> index cb6468adb..84683c547 100644
> --- a/tools/testing/selftests/net/bench/page_pool/bench_page_pool_simple.c
> +++ b/tools/testing/selftests/net/bench/page_pool/bench_page_pool_simple.c
> @@ -16,6 +17,8 @@
> static int verbose = 1;
> #define MY_POOL_SIZE 1024
>
> +DEFINE_MUTEX(wait_for_tasklet);
> +
[ ... ]
> +/* Testing page_pool requires running under softirq.
> + *
> + * Running under a tasklet satisfy this, as tasklets are built on top of
> + * softirq.
> + */
> +static void pp_tasklet_handler(struct tasklet_struct *t)
> +{
> + uint32_t nr_loops = loops;
> +
> + if (in_serving_softirq())
> + pr_warn("%s(): in_serving_softirq fast-path\n",
> + __func__); // True
> + else
> + pr_warn("%s(): Cannot use page_pool fast-path\n", __func__);
> +
> + if (enabled(bit_run_bench_tasklet01))
> + time_bench_loop(nr_loops, 0, "tasklet_page_pool01_fast_path",
> + NULL, time_bench_page_pool01_fast_path);
> +
> + if (enabled(bit_run_bench_tasklet02))
> + time_bench_loop(nr_loops, 0, "tasklet_page_pool02_ptr_ring",
> + NULL, time_bench_page_pool02_ptr_ring);
> +
> + if (enabled(bit_run_bench_tasklet03))
> + time_bench_loop(nr_loops, 0, "tasklet_page_pool03_slow", NULL,
> + time_bench_page_pool03_slow);
> +
> + if (enabled(bit_run_bench_tasklet04))
> + time_bench_loop(nr_loops, 0, "tasklet_page_pool04_napi_aware",
> + NULL, time_bench_page_pool04_napi_aware);
> +
> + mutex_unlock(&wait_for_tasklet); /* Module __init waiting on unlock */
^^^^^^^^^^^^^
Can mutex_unlock() be called from softirq context? The pp_tasklet_handler()
function runs as a tasklet handler in softirq context, but mutexes are
sleeping locks that require process context. Would a completion or spinlock
be more appropriate here?
The synchronization pattern appears to be:
bench_page_pool_simple_module_init()->mutex_lock(&wait_for_tasklet)
bench_page_pool_simple_module_init()->tasklet_schedule(&pp_tasklet)
bench_page_pool_simple_module_init()->mutex_lock(&wait_for_tasklet) [blocks]
pp_tasklet_handler()->mutex_unlock(&wait_for_tasklet) [softirq context]
> +}
> +DECLARE_TASKLET_DISABLED(pp_tasklet, pp_tasklet_handler);
> +
> +static void run_tasklet_tests(void)
> +{
> + tasklet_enable(&pp_tasklet);
> + /* "Async" schedule tasklet, which runs on the CPU that schedule it */
> + tasklet_schedule(&pp_tasklet);
> +}
[ ... ]
> @@ -251,12 +332,19 @@ static int __init
> bench_page_pool_simple_module_init(void)
>
> run_benchmark_tests();
>
> + mutex_lock(&wait_for_tasklet);
> + run_tasklet_tests();
> + /* Sleep on mutex, waiting for tasklet to release */
> + mutex_lock(&wait_for_tasklet);
> +
> return 0;
> }
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/19165940352
