linux-kernel - Re: [PATCH] percpu_ida: Use _irqsave() instead of local_irq_save() + spin

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Date:   Fri, 4 May 2018 20:51:54 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-kernel@...r.kernel.org, tglx@...utronix.de,
        Nicholas Bellinger <nab@...ux-iscsi.org>,
        Shaohua Li <shli@...com>,
        Kent Overstreet <kent.overstreet@...il.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH] percpu_ida: Use _irqsave() instead of local_irq_save() +
 spin_lock

On Fri, May 04, 2018 at 04:22:16PM -0700, Andrew Morton wrote:
> I'm feeling a bit hostile toward lib/percpu_ida.c in general ;) It has
> very few users and seems rather complicated (what's with that
> schedule() in percpu_ida_alloc?).  I'm suspecting and hoping that if
> someone can figure out what the requirements were, this could all be
> zapped and reimplemented using something else which we already have.

Note that I have no code in percpu_ida ... it's quite different from
the regular IDA.  But I have noticed the stunning similarity between the
percpu_ida and the code in lib/sbitmap.c.  I have no idea which one is
better, but they're essentially doing the same thing.