Re: [PATCH v2 2/4] Workqueue: replace use of system_unbound_wq with system_dfl_wq

[Frederic Weisbecker <frederic@kernel.org>]

Le Mon, Aug 25, 2025 at 03:29:04PM +0200, Marco Crivellari a écrit :
> Currently if a user enqueue a work item using schedule_delayed_work() the
> used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
> WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
> schedule_work() that is using system_wq and queue_work(), that makes use
> again of WORK_CPU_UNBOUND.
> 
> This lack of consistentcy cannot be addressed without refactoring the API.
> 
> system_unbound_wq should be the default workqueue so as not to enforce
> locality constraints for random work whenever it's not required.
> 
> Adding system_dfl_wq to encourage its use when unbound work should be used.
> 
> queue_work() / queue_delayed_work() / mod_delayed_work() will now use the
> new unbound wq: whether the user still use the old wq a warn will be
> printed along with a wq redirect to the new one.
> 
> The old system_unbound_wq will be kept for a few release cycles.
> 
> Suggested-by: Tejun Heo <tj@kernel.org>
> Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>

This should be one patch per subsystem. Here is how you can divide that
into a patchset:

> ---
>  drivers/accel/ivpu/ivpu_pm.c                         |  2 +-
>  drivers/acpi/scan.c                                  |  2 +-
>  drivers/base/dd.c                                    |  2 +-
>  drivers/block/zram/zram_drv.c                        |  2 +-
>  drivers/char/random.c                                |  8 ++++----
>  drivers/gpu/drm/amd/amdgpu/aldebaran.c               |  2 +-
>  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c           |  2 +-
>  drivers/gpu/drm/amd/amdgpu/amdgpu_reset.c            |  2 +-
>  drivers/gpu/drm/drm_atomic_helper.c                  |  6 +++---
>  drivers/gpu/drm/i915/display/intel_display_power.c   |  2 +-
>  drivers/gpu/drm/i915/display/intel_tc.c              |  4 ++--
>  drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c         |  2 +-
>  drivers/gpu/drm/i915/gt/uc/intel_guc.c               |  4 ++--
>  drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c            |  4 ++--
>  drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c    |  6 +++---
>  drivers/gpu/drm/i915/i915_active.c                   |  2 +-
>  drivers/gpu/drm/i915/i915_sw_fence_work.c            |  2 +-
>  drivers/gpu/drm/i915/i915_vma_resource.c             |  2 +-
>  drivers/gpu/drm/i915/pxp/intel_pxp.c                 |  2 +-
>  drivers/gpu/drm/i915/pxp/intel_pxp_irq.c             |  2 +-
>  drivers/gpu/drm/nouveau/dispnv50/disp.c              |  2 +-
>  drivers/gpu/drm/rockchip/rockchip_drm_vop.c          |  2 +-
>  drivers/gpu/drm/xe/xe_devcoredump.c                  |  2 +-
>  drivers/gpu/drm/xe/xe_execlist.c                     |  2 +-
>  drivers/gpu/drm/xe/xe_guc_ct.c                       |  4 ++--
>  drivers/gpu/drm/xe/xe_oa.c                           |  2 +-
>  drivers/gpu/drm/xe/xe_vm.c                           |  4 ++--
>  drivers/hte/hte.c                                    |  2 +-
>  drivers/infiniband/core/ucma.c                       |  2 +-
>  drivers/infiniband/hw/mlx5/odp.c                     |  4 ++--
>  drivers/media/platform/synopsys/hdmirx/snps_hdmirx.c |  8 ++++----
>  drivers/net/macvlan.c                                |  2 +-
>  drivers/net/netdevsim/dev.c                          |  6 +++---
>  drivers/net/wireless/intel/iwlwifi/fw/dbg.c          |  4 ++--
>  drivers/net/wireless/intel/iwlwifi/iwl-trans.h       |  2 +-
>  drivers/scsi/qla2xxx/qla_os.c                        |  2 +-
>  drivers/scsi/scsi_transport_iscsi.c                  |  2 +-
>  drivers/soc/xilinx/zynqmp_power.c                    |  6 +++---
>  drivers/target/sbp/sbp_target.c                      |  8 ++++----
>  drivers/tty/serial/8250/8250_dw.c                    |  4 ++--
>  drivers/tty/tty_buffer.c                             |  8 ++++----

One patch for drivers.

>  fs/afs/callback.c                                    |  4 ++--
>  fs/afs/write.c                                       |  2 +-
>  fs/bcachefs/btree_write_buffer.c                     |  2 +-
>  fs/bcachefs/io_read.c                                | 12 ++++++------
>  fs/bcachefs/journal_io.c                             |  2 +-
>  fs/btrfs/block-group.c                               |  2 +-
>  fs/btrfs/extent_map.c                                |  2 +-
>  fs/btrfs/space-info.c                                |  4 ++--
>  fs/btrfs/zoned.c                                     |  2 +-
>  fs/ext4/mballoc.c                                    |  2 +-
>  fs/netfs/objects.c                                   |  2 +-
>  fs/netfs/read_collect.c                              |  2 +-
>  fs/netfs/write_collect.c                             |  2 +-
>  fs/nfsd/filecache.c                                  |  2 +-
>  fs/notify/mark.c                                     |  4 ++--
>  fs/quota/dquot.c                                     |  2 +-

One for fs.

>  include/linux/workqueue.h                            |  4 ++--

One for workqueue.

>  io_uring/io_uring.c                                  |  2 +-

One for io_uring.

>  kernel/bpf/helpers.c                                 |  4 ++--
>  kernel/bpf/memalloc.c                                |  2 +-
>  kernel/bpf/syscall.c                                 |  2 +-

One for bpf.

>  kernel/padata.c                                      |  4 ++--

One for padata.

>  kernel/sched/core.c                                  |  4 ++--
>  kernel/sched/ext.c                                   |  4 ++--

One for scheduler.

>  kernel/umh.c                                         |  2 +-

One for umh.

>  kernel/workqueue.c                                   |  2 +-

Should join the workqueue change above.

>  mm/backing-dev.c                                     |  2 +-
>  mm/kfence/core.c                                     |  6 +++---
>  mm/memcontrol.c                                      |  4 ++--

One for mm.

>  net/core/link_watch.c                                |  4 ++--
>  net/unix/garbage.c                                   |  2 +-
>  net/wireless/core.c                                  |  4 ++--
>  net/wireless/sysfs.c                                 |  2 +-

One for net.

>  rust/kernel/workqueue.rs                             |  6 +++---

This can join the workqueue changes above.

>  sound/soc/codecs/wm_adsp.c                           |  2 +-

And finally one for sound.

Thanks!

-- 
Frederic Weisbecker
SUSE Labs