linux-kernel - Re: [PATCH v6 2/3] uacce: add uacce driver

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Date:   Fri, 25 Oct 2019 09:35:38 +0200
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     "zhangfei.gao@...mail.com" <zhangfei.gao@...mail.com>
Cc:     Zhangfei Gao <zhangfei.gao@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        jonathan.cameron@...wei.com, grant.likely@....com,
        ilias.apalodimas@...aro.org, francois.ozog@...aro.org,
        kenneth-lee-2012@...mail.com, Wangzhou <wangzhou1@...ilicon.com>,
        "haojian . zhuang" <haojian.zhuang@...aro.org>,
        linux-accelerators@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org, Kenneth Lee <liguozhu@...ilicon.com>,
        Zaibo Xu <xuzaibo@...wei.com>
Subject: Re: [PATCH v6 2/3] uacce: add uacce driver

On Fri, Oct 25, 2019 at 10:28:30AM +0800, zhangfei.gao@...mail.com wrote:
> > Something else I noticed is uacce_idr isn't currently protected. The IDR
> > API expected the caller to use its own locking scheme. You could replace
> > it with an xarray, which I think is preferred to IDR now and provides a
> > xa_lock.
> Currently  idr_alloc and idr_remove are simply protected by uacce_mutex,

Ah right, but idr_find() also needs to be protected? 

> Will check xarray, looks it is more complicated then idr.

Having tried both, it can easily replace idr. For uacce I think it could
be something like (locking included):

	static DEFINE_XARRAY_ALLOC(uacce_xa);

	uacce = xa_load(&uacce_xa, iminor(inode));

	ret = xa_alloc(&uacce_xa, &uacce->dev_id, uacce, xa_limit_32b,
		       GFP_KERNEL);

	xa_erase(&uacce_xa, uacce->dev_id);

Thanks,
Jean