Re: [PATCH v2 4/6] rust: workqueue: add creation of workqueues

On Fri Aug 7, 2026 at 6:52 PM CEST, Danilo Krummrich wrote:
>   * new_power_efficient(): WQ_UNBOUND | WQ_POWER_EFFICIENT, add
>     .percpu(),

[...]

> +    pub fn new_power_efficient() -> Builder<TypePowerEfficient> {
> +        Builder {
> +            flags: bindings::wq_flags_WQ_UNBOUND | bindings::wq_flags_WQ_POWER_EFFICIENT,

I actually meant to add WQ_PERCPU, which should be the default for
WQ_POWER_EFFICIENT, in order to avoid the warning below.

But I somehow managed to fix it the wrong way around and made WQ_UNBOUND the
default.

So, this should just be bindings::wq_flags_WQ_PERCPU |
bindings::wq_flags_WQ_POWER_EFFICIENT.

- Danilo

[    1.381581] workqueue: my-wq is using neither WQ_PERCPU or WQ_UNBOUND. Setting WQ_PERCPU.
[    1.382274] WARNING: kernel/workqueue.c:5852 at alloc_workqueue_va+0x794/0x800, CPU#0: kunit_try_catch/851
[    1.383088] Modules linked in:
[    1.383359] CPU: 0 UID: 0 PID: 851 Comm: kunit_try_catch Tainted: G        W        N  7.2.0-rc1+ #67 PREEMPT(full)
[    1.384236] Tainted: [W]=WARN, [N]=TEST
[    1.384567] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.17.0-2-2 04/01/2014
[    1.385364] RIP: 0010:alloc_workqueue_va+0x79b/0x800
[    1.385784] Code: 49 8d 96 b8 00 00 00 b9 01 00 00 00 41 b8 00 08 00 00 e8 08 83 ef ff e9 88 f9 ff ff 48 8d 3d cc 1c e2 01 49 8d b6 b8 00 00 00 <67> 48 0f b9 3a 41 81 cc 00 01 00 00 e9 40 f9 ff ff 48 8d 3d bd 1c
[    1.387337] RSP: 0018:ffffc90000473d58 EFLAGS: 00010246
[    1.387779] RAX: 0000000000000000 RBX: ffff888102041600 RCX: 8313f7e158b49600
[    1.388382] RDX: ffff8881020416d8 RSI: ffff8881020416b8 RDI: ffffffff8312e020
[    1.388985] RBP: 0000000000000000 R08: 00000000ffffffff R09: 00000000ffffffff
[    1.389587] R10: ffff8881020416bd R11: 0000000000000000 R12: 0000000000000080
[    1.390192] R13: ffffffff82ad53fd R14: ffff888102041600 R15: ffffc90000473de0
[    1.390793] FS:  0000000000000000(0000) GS:ffff8881b81cf000(0000) knlGS:0000000000000000
[    1.391478] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    1.391968] CR2: ffff88813ffff000 CR3: 0000000002e22000 CR4: 0000000000750ef0
[    1.392568] PKRU: 55555554
[    1.392804] Call Trace:
[    1.393027]  <TASK>
[    1.393219]  alloc_workqueue_noprof+0x5b/0x80
[    1.393594]  rust_doctest_kernel_workqueue_builder_rs_12+0x3a/0x1f0
[    1.394129]  ? _task_rq_lock+0x55/0x150
[    1.394462]  ? call_rcu+0xec/0x270
[    1.394756]  ? kvm_clock_get_cycles+0x18/0x40
[    1.395136]  ? ktime_get_ts64+0x6d/0x170
[    1.395477]  kunit_try_run_case+0x93/0x190
[    1.395826]  kunit_generic_run_threadfn_adapter+0x22/0x40
[    1.396290]  ? kunit_try_catch_run+0x210/0x210
[    1.396670]  kthread+0xfb/0x120
[    1.396942]  ? kthread_blkcg+0x40/0x40
[    1.397270]  ret_from_fork+0xee/0x260
[    1.397590]  ? kthread_blkcg+0x40/0x40
[    1.397910]  ret_from_fork_asm+0x11/0x20
[    1.398255]  </TASK>
[    1.398453] ---[ end trace 0000000000000000 ]---