linux-kernel - Re: [PATCH v39 16/24] x86/sgx: Add a page reclaimer

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Date:   Mon, 5 Oct 2020 01:39:21 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Haitao Huang <haitao.huang@...ux.intel.com>
Cc:     x86@...nel.org, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Jethro Beekman <jethro@...tanix.com>,
        Jordan Hand <jorhand@...ux.microsoft.com>,
        Nathaniel McCallum <npmccallum@...hat.com>,
        Chunyang Hui <sanqian.hcy@...fin.com>,
        Seth Moore <sethmo@...gle.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        akpm@...ux-foundation.org, andriy.shevchenko@...ux.intel.com,
        asapek@...gle.com, bp@...en8.de, cedric.xing@...el.com,
        chenalexchen@...gle.com, conradparker@...gle.com,
        cyhanish@...gle.com, dave.hansen@...el.com, kai.huang@...el.com,
        kai.svahn@...el.com, kmoy@...gle.com, ludloff@...gle.com,
        luto@...nel.org, nhorman@...hat.com, puiterwijk@...hat.com,
        rientjes@...gle.com, tglx@...utronix.de, yaozhangx@...gle.com,
        mikko.ylinen@...el.com, willy@...radead.org
Subject: Re: [PATCH v39 16/24] x86/sgx: Add a page reclaimer

On Sat, Oct 03, 2020 at 01:23:49PM -0500, Haitao Huang wrote:
> On Sat, 03 Oct 2020 08:32:45 -0500, Jarkko Sakkinen
> <jarkko.sakkinen@...ux.intel.com> wrote:
> 
> > On Sat, Oct 03, 2020 at 12:22:47AM -0500, Haitao Huang wrote:
> > > When I turn on CONFIG_PROVE_LOCKING, kernel reports following
> > > suspicious RCU
> > > usages. Not sure if it is an issue. Just reporting here:
> > 
> > I'm glad to hear that my tip helped you to get us the data.
> > 
> > This does not look like an issue in the page reclaimer, which was not
> > obvious for me before. That's a good thing. I was really worried about
> > that because it has been very stable for a long period now. The last
> > bug fix for the reclaimer was done in June in v31 version of the patch
> > set and after that it has been unchanged (except possibly some renames
> > requested by Boris).
> > 
> > I wildly guess I have a bad usage pattern for xarray. I migrated to it
> > in v36, and it is entirely possible that I've misused it. It was the
> > first time that I ever used it. Before xarray we had radix_tree but
> > based Matthew Wilcox feedback I did a migration to xarray.
> > 
> > What I'd ask you to do next is to, if by any means possible, to try to
> > run the same test with v35 so we can verify this. That one still has
> > the radix tree.
> > 
> 
> 
> v35 does not cause any such warning messages from kernel

Thank you. Looks like Matthew already located the issue, a fix will
land soon.

/Jarkko