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Date:   Wed, 6 Mar 2019 08:35:21 -0800
From:   Dan Williams <>
To:     Yongxin Liu <>
Cc:     Linux Kernel Mailing List <>,,
        Sebastian Andrzej Siewior <>,
        Thomas Gleixner <>,
        Steven Rostedt <>,
        Pankaj Gupta <>,
        Paul Gortmaker <>,
        linux-nvdimm <>
Subject: Re: [PATCH RT] nvdimm: make lane acquirement RT aware

On Wed, Mar 6, 2019 at 2:05 AM Yongxin Liu <> wrote:
> Currently, nvdimm driver isn't RT compatible.
> nd_region_acquire_lane() disables preemption with get_cpu() which
> causes "scheduling while atomic" spews on RT, when using fio to test
> pmem as block device.
> In this change, we replace get_cpu/put_cpu with local_lock_cpu/
> local_unlock_cpu, and introduce per CPU variable "ndl_local_lock".
> Due to preemption on RT, this lock can avoid race condition for the
> same lane on the same CPU. When CPU number is greater than the lane
> number, lane can be shared among CPUs. "ndl_lock->lock" is used to
> protect the lane in this situation.
> This patch is derived from Dan Williams and Pankaj Gupta's proposal from
> and
> Many thanks to them.
> Cc: Dan Williams <>
> Cc: Pankaj Gupta <>
> Cc: linux-rt-users <>
> Cc: linux-nvdimm <>
> Signed-off-by: Yongxin Liu <>

Looks ok to me in concept.

Acked-by: Dan Williams <>

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