linux-kernel - Re: [PATCH RT] nvdimm: make lane acquirement RT aware

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Message-ID: <20190307143344.ytsnbmot5tjzjhip@linutronix.de>
Date:   Thu, 7 Mar 2019 15:33:44 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Yongxin Liu <yongxin.liu@...driver.com>
Cc:     linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
        tglx@...utronix.de, rostedt@...dmis.org, dan.j.williams@...el.com,
        pagupta@...hat.com, paul.gortmaker@...driver.com,
        linux-nvdimm@...ts.01.org
Subject: Re: [PATCH RT] nvdimm: make lane acquirement RT aware

On 2019-03-06 17:57:09 [+0800], Yongxin Liu wrote:
> 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.

so what was the reason that get_cpu() can't be replaced with
raw_smp_processor_id()?

Sebastian