linux-kernel - Re: [RESEND PATCH 1/3] completion: Add support for initializing completion with lockdep

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Date:   Fri, 20 Oct 2017 15:14:06 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     Bart Van Assche <Bart.VanAssche@....com>
Cc:     "mingo@...nel.org" <mingo@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "amir73il@...il.com" <amir73il@...il.com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "hch@...radead.org" <hch@...radead.org>,
        "linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "oleg@...hat.com" <oleg@...hat.com>,
        "darrick.wong@...cle.com" <darrick.wong@...cle.com>,
        "johannes.berg@...el.com" <johannes.berg@...el.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "idryomov@...il.com" <idryomov@...il.com>,
        "tj@...nel.org" <tj@...nel.org>,
        "kernel-team@....com" <kernel-team@....com>,
        "david@...morbit.com" <david@...morbit.com>
Subject: Re: [RESEND PATCH 1/3] completion: Add support for initializing
 completion with lockdep_map

On Thu, Oct 19, 2017 at 11:24:00PM +0000, Bart Van Assche wrote:
> Are there any completion objects for which the cross-release checking is
> useful? Are there any wait_for_completion() callers that hold a mutex or
> other locking object?

Check /proc/lockdep, then you can find all dependencies wrt cross-lock.
I named a lock class of wait_for_completion(), a sting starting with
"(complete)".

For example, in my machine:

console_lock -> (complete)&req.done
cpu_hotplug_lock.rw_sem -> (complete)&st->done_up
cpuhp_state_mutex -> (complete)&st->done_up

and so on.