linux-kernel - Re: [PATCH 04/10] staging: erofs: fix `erofs_workgroup_{try_to

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Message-ID: <20181122102155.GE3189@kroah.com>
Date:   Thu, 22 Nov 2018 11:21:55 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Gao Xiang <gaoxiang25@...wei.com>
Cc:     devel@...verdev.osuosl.org, linux-erofs@...ts.ozlabs.org,
        Chao Yu <yuchao0@...wei.com>,
        LKML <linux-kernel@...r.kernel.org>, weidu.du@...wei.com,
        Miao Xie <miaoxie@...wei.com>
Subject: Re: [PATCH 04/10] staging: erofs: fix
 `erofs_workgroup_{try_to_freeze, unfreeze}'

On Tue, Nov 20, 2018 at 10:34:19PM +0800, Gao Xiang wrote:
> There are two minor issues in the current freeze interface:
> 
>    1) Freeze interfaces have not related with CONFIG_DEBUG_SPINLOCK,
>       therefore fix the incorrect conditions;
> 
>    2) For SMP platforms, it should also disable preemption before
>       doing atomic_cmpxchg in case that some high priority tasks
>       preempt between atomic_cmpxchg and disable_preempt, then spin
>       on the locked refcount later.

spinning on a refcount implies that you are trying to do your own type
of locking.  Why not use the in-kernel locking api instead?  It will
always do better than trying to do your own logic as the developers
there know locking across all types of cpus better than filesystem
developers :)

thanks,

greg k-h