linux-kernel - Re: [PATCH] PM / wakeup: use seq

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Date:   Fri, 2 Mar 2018 10:12:01 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Pavel Machek <pavel@....cz>
Cc:     Ganesh Mahendran <opensource.ganesh@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PM / wakeup: use seq_open() to show wakeup stats

On Fri, Mar 2, 2018 at 10:05 AM, Pavel Machek <pavel@....cz> wrote:
> On Fri 2018-03-02 13:01:00, Ganesh Mahendran wrote:
>> single_open() interface requires that the whole output must
>> fit into a single buffer. This will lead to timeout when
>> system memory is not in a good situation.
>>
>> This patch use seq_open() to show wakeup stats. This method
>> need only one page, so timeout will not be observed.
>
> Can the rcu_read_unlock be delayed arbitrarily by userland code?
>
> Is that ok with RCU?

No, it isn't. :-)