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Date:   Thu, 13 Aug 2020 02:38:20 +0000
From:   Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>
To:     Logan Gunthorpe <logang@...tatee.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        Keith Busch <kbusch@...nel.org>
CC:     Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
        Keith Busch <Keith.Busch@....com>, Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH v2] nvme: Use spin_lock_irq() when taking the ctrl->lock

On 8/12/20 16:25, Logan Gunthorpe wrote:
> When locking the ctrl->lock spinlock IRQs need to be disabled to avoid a
> dead lock. The new spin_lock() calls recently added produce the
> following lockdep warning when running the blktest nvme/003:
> 
>      ================================
>      WARNING: inconsistent lock state
>      --------------------------------
>      inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
>      ksoftirqd/2/22 [HC0[0]:SC1[1]:HE0:SE0] takes:
>      ffff888276a8c4c0 (&ctrl->lock){+.?.}-{2:2}, at: nvme_keep_alive_end_io+0x50/0xc0
>      {SOFTIRQ-ON-W} state was registered at:
>        lock_acquire+0x164/0x500
>        _raw_spin_lock+0x28/0x40
>        nvme_get_effects_log+0x37/0x1c0
>        nvme_init_identify+0x9e4/0x14f0
>        nvme_reset_work+0xadd/0x2360
>        process_one_work+0x66b/0xb70
>        worker_thread+0x6e/0x6c0
>        kthread+0x1e7/0x210
>        ret_from_fork+0x22/0x30
>      irq event stamp: 1449221
>      hardirqs last  enabled at (1449220): [<ffffffff81c58e69>] ktime_get+0xf9/0x140
>      hardirqs last disabled at (1449221): [<ffffffff83129665>] _raw_spin_lock_irqsave+0x25/0x60
>      softirqs last  enabled at (1449210): [<ffffffff83400447>] __do_softirq+0x447/0x595
>      softirqs last disabled at (1449215): [<ffffffff81b489b5>] run_ksoftirqd+0x35/0x50
> 
>      other info that might help us debug this:
>       Possible unsafe locking scenario:
> 
>             CPU0
>             ----
>        lock(&ctrl->lock);
>        <Interrupt>
>          lock(&ctrl->lock);
> 
>       *** DEADLOCK ***
> 
>      no locks held by ksoftirqd/2/22.
> 
>      stack backtrace:
>      CPU: 2 PID: 22 Comm: ksoftirqd/2 Not tainted 5.8.0-rc4-eid-vmlocalyes-dbg-00157-g7236657c6b3a #1450
>      Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.12.0-1 04/01/2014
>      Call Trace:
>       dump_stack+0xc8/0x11a
>       print_usage_bug.cold.63+0x235/0x23e
>       mark_lock+0xa9c/0xcf0
>       __lock_acquire+0xd9a/0x2b50
>       lock_acquire+0x164/0x500
>       _raw_spin_lock_irqsave+0x40/0x60
>       nvme_keep_alive_end_io+0x50/0xc0
>       blk_mq_end_request+0x158/0x210
>       nvme_complete_rq+0x146/0x500
>       nvme_loop_complete_rq+0x26/0x30 [nvme_loop]
>       blk_done_softirq+0x187/0x1e0
>       __do_softirq+0x118/0x595
>       run_ksoftirqd+0x35/0x50
>       smpboot_thread_fn+0x1d3/0x310
>       kthread+0x1e7/0x210
>       ret_from_fork+0x22/0x30
> 
> Fixes: be93e87e7802 ("nvme: support for multiple Command Sets Supported and Effects log pages")
> Signed-off-by: Logan Gunthorpe<logang@...tatee.com>

Thanks for this fix, looks good.

Tested-by: Chaitanya Kulkarni <chaitanya.kulkarni@....com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@....com>

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