Messages in this thread Patch in this message | | | Date | Wed, 2 Oct 2019 15:21:36 +0300 | From | Mika Westerberg <> | Subject | System hangs if NVMe/SSD is removed during suspend |
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Hi Tejun,
In a system with Thunderbolt connected NVMe or SSD entering system suspend, detaching the NVMe/SSD and resuming the system hangs (see also https://bugzilla.kernel.org/show_bug.cgi?id=204385).
Triggering sysrq-w I see this:
[ 113.093783] Workqueue: nvme-wq nvme_remove_dead_ctrl_work [nvme] [ 113.095156] Call Trace: [ 113.096234] ? __schedule+0x2c5/0x630 [ 113.097409] ? wait_for_completion+0xa4/0x120 [ 113.098639] schedule+0x3e/0xc0 [ 113.099769] schedule_timeout+0x1c9/0x320 [ 113.100973] ? resched_curr+0x1f/0xd0 [ 113.102146] ? wait_for_completion+0xa4/0x120 [ 113.103379] wait_for_completion+0xc3/0x120 [ 113.104595] ? wake_up_q+0x60/0x60 [ 113.105749] __flush_work+0x131/0x1e0 [ 113.106925] ? flush_workqueue_prep_pwqs+0x130/0x130 [ 113.108215] bdi_unregister+0xb9/0x130 [ 113.109403] del_gendisk+0x2d2/0x2e0 [ 113.110580] nvme_ns_remove+0xed/0x110 [nvme_core] [ 113.111853] nvme_remove_namespaces+0x96/0xd0 [nvme_core] [ 113.113177] nvme_remove+0x5b/0x160 [nvme] [ 113.114391] pci_device_remove+0x36/0x90 [ 113.115590] device_release_driver_internal+0xdf/0x1c0 [ 113.116893] nvme_remove_dead_ctrl_work+0x14/0x30 [nvme] [ 113.118217] process_one_work+0x1c2/0x3f0 [ 113.119434] worker_thread+0x48/0x3e0 [ 113.120619] kthread+0x100/0x140 [ 113.121772] ? current_work+0x30/0x30 [ 113.122955] ? kthread_park+0x80/0x80 [ 113.124142] ret_from_fork+0x35/0x40
The exact place is in wb_shutdown():
/* * Drain work list and shutdown the delayed_work. !WB_registered * tells wb_workfn() that @wb is dying and its work_list needs to * be drained no matter what. */ mod_delayed_work(bdi_wq, &wb->dwork, 0); flush_delayed_work(&wb->dwork);
Now bdi_wq is marked as WQ_FREEZABLE and at this time we are still resuming devices so I think it is still frozen. This basically results that the resume process is waiting for bdi_unregister() but it cannot progress because its workqueue is still frozen.
I saw you "dealt" similar situation for libata with commit 85fbd722ad0f ("libata, freezer: avoid block device removal while system is frozen") and that there was discussion around this here:
https://marc.info/?l=linux-kernel&m=138695698516487
but from that discussion I don't see more generic solution to be implemented.
Any ideas we should fix this properly?
I mean nowadays Thunderbolt connected storage is quite common and I suppose situation like this might wery well happen, say you have a dock with SSD connected and you disconnect it when the laptop is suspended.
I've been using following hack to prevent the issue but I'm quite sure there is a better solution ;-)
Thanks in advance!
drivers/ata/libata-scsi.c | 2 ++ mm/backing-dev.c | 4 ++-- 2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c index 76d0f9de767b..3fea8d72f6f9 100644 --- a/drivers/ata/libata-scsi.c +++ b/drivers/ata/libata-scsi.c @@ -4791,6 +4791,7 @@ void ata_scsi_hotplug(struct work_struct *work) return; } +#if 0 /* * XXX - UGLY HACK * @@ -4810,6 +4811,7 @@ void ata_scsi_hotplug(struct work_struct *work) #ifdef CONFIG_FREEZER while (pm_freezing) msleep(10); +#endif #endif DPRINTK("ENTER\n"); diff --git a/mm/backing-dev.c b/mm/backing-dev.c index e8e89158adec..8e77711d5dd0 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -236,8 +236,8 @@ static int __init default_bdi_init(void) { int err; - bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE | - WQ_UNBOUND | WQ_SYSFS, 0); + bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND | + WQ_SYSFS, 0); if (!bdi_wq) return -ENOMEM;
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