[PATCH V2 1/1] nvme: fix multiple ctrl removal scheduling

Rakesh Pandit
2017-05-24T14:26:29Z

Commit c5f6ce97c1210 tries to address multiple resets but fails as
work_busy doesn't involve any synchronization and can fail. This is
reproducible easily as can be seen by WARNING below which is triggered
with line:

WARN_ON(dev->ctrl.state == NVME_CTRL_RESETTING)

Allowing multiple resets can result in multiple controller removal as
well if different conditions inside nvme_reset_work fail and which
might deadlock on device_release_driver.

This patch makes sure that work queue item (reset_work) is added only
if controller state != NVME_CTRL_RESETTING and that is achieved by
moving state change outside nvme_reset_work into nvme_reset and
removing old work_busy call. State change is always synchronizated
using controller spinlock.

[ 480.327007] WARNING: CPU: 3 PID: 150 at drivers/nvme/host/pci.c:1900 nvme_reset_work+0x36c/0xec0
[ 480.327008] Modules linked in: rfcomm fuse nf_conntrack_netbios_ns nf_conntrack_broadcast...
[ 480.327044] btusb videobuf2_core ghash_clmulni_intel snd_hwdep cfg80211 acer_wmi hci_uart..
[ 480.327065] CPU: 3 PID: 150 Comm: kworker/u16:2 Not tainted 4.12.0-rc1+ #13
[ 480.327065] Hardware name: Acer Predator G9-591/Mustang_SLS, BIOS V1.10 03/03/2016
[ 480.327066] Workqueue: nvme nvme_reset_work
[ 480.327067] task: ffff880498ad8000 task.stack: ffffc90002218000
[ 480.327068] RIP: 0010:nvme_reset_work+0x36c/0xec0
[ 480.327069] RSP: 0018:ffffc9000221bdb8 EFLAGS: 00010246
[ 480.327070] RAX: 0000000000460000 RBX: ffff880498a98128 RCX: dead000000000200
[ 480.327070] RDX: 0000000000000001 RSI: ffff8804b1028020 RDI: ffff880498a98128
[ 480.327071] RBP: ffffc9000221be50 R08: 0000000000000000 R09: 0000000000000000
[ 480.327071] R10: ffffc90001963ce8 R11: 000000000000020d R12: ffff880498a98000
[ 480.327072] R13: ffff880498a53500 R14: ffff880498a98130 R15: ffff880498a98128
[ 480.327072] FS: 0000000000000000(0000) GS:ffff8804c1cc0000(0000) knlGS:0000000000000000
[ 480.327073] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 480.327074] CR2: 00007ffcf3c37f78 CR3: 0000000001e09000 CR4: 00000000003406e0
[ 480.327074] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 480.327075] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 480.327075] Call Trace:
[ 480.327079] ? __switch_to+0x227/0x400
[ 480.327081] process_one_work+0x18c/0x3a0
[ 480.327082] worker_thread+0x4e/0x3b0
[ 480.327084] kthread+0x109/0x140
[ 480.327085] ? process_one_work+0x3a0/0x3a0
[ 480.327087] ? kthread_park+0x60/0x60
[ 480.327102] ret_from_fork+0x2c/0x40
[ 480.327103] Code: e8 5a dc ff ff 85 c0 41 89 c1 0f.....

V2: Use controller state to solve the problem (suggested by Christoph Hellwig)
Fixes: c5f6ce97c1210 ("nvme: don't schedule multiple resets")
Signed-off-by: Rakesh Pandit <rakesh@tuxera.com>
---
drivers/nvme/host/pci.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 4c2ff2b..ba54e2a 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1903,9 +1903,6 @@ static void nvme_reset_work(struct work_struct *work)
bool was_suspend = !!(dev->ctrl.ctrl_config & NVME_CC_SHN_NORMAL);
int result = -ENODEV;

- if (WARN_ON(dev->ctrl.state == NVME_CTRL_RESETTING))
- goto out;
-
/*
* If we're called to reset a live controller first shut it down before
* moving on.
@@ -1913,9 +1910,6 @@ static void nvme_reset_work(struct work_struct *work)
if (dev->ctrl.ctrl_config & NVME_CC_ENABLE)
nvme_dev_disable(dev, false);

- if (!nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESETTING))
- goto out;
-
result = nvme_pci_enable(dev);
if (result)
goto out;
@@ -2009,8 +2003,8 @@ static int nvme_reset(struct nvme_dev *dev)
{
if (!dev->ctrl.admin_q || blk_queue_dying(dev->ctrl.admin_q))
return -ENODEV;
- if (work_busy(&dev->reset_work))
- return -ENODEV;
+ if (!nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RESETTING))
+ return -EBUSY;
if (!queue_work(nvme_workq, &dev->reset_work))
return -EBUSY;
return 0;
--
2.5.5