On Wed, Feb 24, 2021 at 11:18:50AM +0100, Loic Poulain wrote:
> A recent change created a dedicated workqueue for the state-change work
> with WQ_HIGHPRI (no strong reason for that) and WQ_MEM_RECLAIM flags,
> but the state-change work (mhi_pm_st_worker) does not guarantee forward
> progress under memory pressure, and will even wait on various memory
> allocations when e.g. creating devices, loading firmware, etc... The
> work is then not part of a memory reclaim path...
>
> Moreover, this causes a warning in check_flush_dependency() since we end
> up in code that flushes a non-reclaim workqueue:
>
> [ 40.969601] workqueue: WQ_MEM_RECLAIM mhi_hiprio_wq:mhi_pm_st_worker [mhi] is flushing !WQ_MEM_RECLAIM events_highpri:flush_backlog
> [ 40.969612] WARNING: CPU: 4 PID: 158 at kernel/workqueue.c:2607 check_flush_dependency+0x11c/0x140
> [ 40.969733] Call Trace:
> [ 40.969740] __flush_work+0x97/0x1d0
> [ 40.969745] ? wake_up_process+0x15/0x20
> [ 40.969749] ? insert_work+0x70/0x80
> [ 40.969750] ? __queue_work+0x14a/0x3e0
> [ 40.969753] flush_work+0x10/0x20
> [ 40.969756] rollback_registered_many+0x1c9/0x510
> [ 40.969759] unregister_netdevice_queue+0x94/0x120
> [ 40.969761] unregister_netdev+0x1d/0x30
> [ 40.969765] mhi_net_remove+0x1a/0x40 [mhi_net]
> [ 40.969770] mhi_driver_remove+0x124/0x250 [mhi]
> [ 40.969776] device_release_driver_internal+0xf0/0x1d0
> [ 40.969778] device_release_driver+0x12/0x20
> [ 40.969782] bus_remove_device+0xe1/0x150
> [ 40.969786] device_del+0x17b/0x3e0
> [ 40.969791] mhi_destroy_device+0x9a/0x100 [mhi]
> [ 40.969796] ? mhi_unmap_single_use_bb+0x50/0x50 [mhi]
> [ 40.969799] device_for_each_child+0x5e/0xa0
> [ 40.969804] mhi_pm_st_worker+0x921/0xf50 [mhi]
>
> Fixes: 8f7039787687 ("bus: mhi: core: Move to using high priority workqueue")
> Signed-off-by: Loic Poulain <loic.poulain@xxxxxxxxxx>
Fix looks good to me but I want Bhaumik to share his review since he
authored the offending patch.
Thanks,
Mani
> ---
> drivers/bus/mhi/core/init.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
> index 32eb90f..03ddd6e 100644
> --- a/drivers/bus/mhi/core/init.c
> +++ b/drivers/bus/mhi/core/init.c
> @@ -890,8 +890,7 @@ int mhi_register_controller(struct mhi_controller *mhi_cntrl,
> INIT_WORK(&mhi_cntrl->st_worker, mhi_pm_st_worker);
> init_waitqueue_head(&mhi_cntrl->state_event);
>
> - mhi_cntrl->hiprio_wq = alloc_ordered_workqueue
> - ("mhi_hiprio_wq", WQ_MEM_RECLAIM | WQ_HIGHPRI);
> + mhi_cntrl->hiprio_wq = alloc_ordered_workqueue("mhi_hiprio_wq", WQ_HIGHPRI);
> if (!mhi_cntrl->hiprio_wq) {
> dev_err(mhi_cntrl->cntrl_dev, "Failed to allocate workqueue\n");
> ret = -ENOMEM;
> --
> 2.7.4
>
