netdev - Re: [PATCH] bpf: test_run: Fix timer mode initialization to NO

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Message-ID: <ba3c0f8c-98b3-4529-9752-a5db2067e235@linux.dev>
Date: Thu, 9 Oct 2025 20:43:09 -0700
From: Yonghong Song <yonghong.song@...ux.dev>
To: Brahmajit Das <listout@...tout.xyz>,
 d0fdced7-a9a5-473e-991f-4f5e4c13f616@...ux.dev
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
 chandna.linuxkernel@...il.com, daniel@...earbox.net,
 david.hunter.linux@...il.com, haoluo@...gle.com, john.fastabend@...il.com,
 jolsa@...nel.org, khalid@...nel.org, martin.lau@...ux.dev,
 netdev@...r.kernel.org, skhan@...uxfoundation.org, song@...nel.org,
 syzbot+1f1fbecb9413cdbfbef8@...kaller.appspotmail.com
Subject: Re: [PATCH] bpf: test_run: Fix timer mode initialization to
 NO_MIGRATE mode



On 10/9/25 4:10 PM, Brahmajit Das wrote:
> On 10.10.2025 04:20, Brahmajit Das wrote:
>> Yonghong Song,
>>
>>> So I suspect that we can remove NO_PREEMPT/NO_MIGRATE in test_run.c
>>> and use migrate_disable()/migrate_enable() universally.
>> Would something like this work?
>>
> Or we can do something like this to completely remove
> NO_PREEMPT/NO_MIGRATE.
>
> --- a/net/bpf/test_run.c
> +++ b/net/bpf/test_run.c
> @@ -29,7 +29,6 @@
>   #include <trace/events/bpf_test_run.h>
>
>   struct bpf_test_timer {
> -       enum { NO_PREEMPT, NO_MIGRATE } mode;
>          u32 i;
>          u64 time_start, time_spent;
>   };
> @@ -38,10 +37,7 @@ static void bpf_test_timer_enter(struct bpf_test_timer *t)
>          __acquires(rcu)
>   {
>          rcu_read_lock();
> -       if (t->mode == NO_PREEMPT)
> -               preempt_disable();
> -       else
> -               migrate_disable();
> +       migrate_disable();
>
>          t->time_start = ktime_get_ns();
>   }
> @@ -51,10 +47,7 @@ static void bpf_test_timer_leave(struct bpf_test_timer *t)
>   {
>          t->time_start = 0;
>
> -       if (t->mode == NO_PREEMPT)
> -               preempt_enable();
> -       else
> -               migrate_enable();
> +       migrate_enable();
>          rcu_read_unlock();
>   }
>
> @@ -374,7 +367,7 @@ static int bpf_test_run_xdp_live(struct bpf_prog *prog, struct xdp_buff *ctx,
>
>   {
>          struct xdp_test_data xdp = { .batch_size = batch_size };
> -       struct bpf_test_timer t = { .mode = NO_MIGRATE };
> +       struct bpf_test_timer t = {};
>          int ret;
>
>          if (!repeat)
> @@ -404,7 +397,7 @@ static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
>          struct bpf_prog_array_item item = {.prog = prog};
>          struct bpf_run_ctx *old_ctx;
>          struct bpf_cg_run_ctx run_ctx;
> -       struct bpf_test_timer t = { NO_MIGRATE };
> +       struct bpf_test_timer t = {};
>          enum bpf_cgroup_storage_type stype;
>          int ret;
>
> @@ -1377,7 +1370,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
>                                       const union bpf_attr *kattr,
>                                       union bpf_attr __user *uattr)
>   {
> -       struct bpf_test_timer t = { NO_PREEMPT };
> +       struct bpf_test_timer t = {};
>          u32 size = kattr->test.data_size_in;
>          struct bpf_flow_dissector ctx = {};
>          u32 repeat = kattr->test.repeat;
> @@ -1445,7 +1438,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
>   int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog, const union bpf_attr *kattr,
>                                  union bpf_attr __user *uattr)
>   {
> -       struct bpf_test_timer t = { NO_PREEMPT };
> +       struct bpf_test_timer t = {};
>          struct bpf_prog_array *progs = NULL;
>          struct bpf_sk_lookup_kern ctx = {};
>          u32 repeat = kattr->test.repeat;
>
> Basically RFC. I posted a patch, wasn't aware that work was already
> going on.

The above sounds good to me.We should remove enum { NO_PREEMPT, NO_MIGRATE } mode;
in struct bpf_test_timer.