linux-kernel - Re: [PATCH v6 1/2] pid: Replace pid bitmap implementation with IDR API

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Message-Id: <20171011153716.5cd0689bb7030b886b0d62f9@linux-foundation.org>
Date:   Wed, 11 Oct 2017 15:37:16 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Gargi Sharma <gs051095@...il.com>
Cc:     linux-kernel@...r.kernel.org, riel@...riel.com,
        julia.lawall@...6.fr, mingo@...nel.org, pasha.tatashin@...cle.com,
        ktkhai@...tuozzo.com, oleg@...hat.com, ebiederm@...ssion.com,
        hch@...radead.org, lkp@...el.com, tony.luck@...el.com
Subject: Re: [PATCH v6 1/2] pid: Replace pid bitmap implementation with IDR
 API

On Wed, 11 Oct 2017 18:19:38 -0400 Gargi Sharma <gs051095@...il.com> wrote:

> This patch replaces the current bitmap implemetation for
> Process ID allocation. Functions that are no longer required,
> for example, free_pidmap(), alloc_pidmap(), etc. are removed.
> The rest of the functions are modified to use the IDR API.
> The change was made to make the PID allocation less complex by
> replacing custom code with calls to generic API.

I still don't understand the locking.  spin_lock_irq(&pidmap_lock) in
some places, rcu_read_lock() in others.

If the locking is indeed now correct, can we please get it fully
documented?  A comment at the pid_namespace.idr definition site would
suit.