linux-kernel - Re: Why CMA allocater fails if there is a signal pending?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 25 Mar 2019 10:26:33 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Peter Chen <hzpeterchen@...il.com>
Cc:     Michal Nazarewicz <mina86@...a86.com>, peter.chen@....com,
        fugang.duan@....com, linux-usb@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: Why CMA allocater fails if there is a signal pending?

On Mon, Mar 25, 2019 at 04:37:09PM +0800, Peter Chen wrote:
> Hi Michal & Marek,
> 
> I meet an issue that the DMA (CMA used) allocation failed if there is a user
> signal, Eg Ctrl+C, it causes the USB xHCI stack fails to resume due to
> dma_alloc_coherent
> failed. It can be easy to reproduce if the user press Ctrl+C at
> suspend/resume test.

It has been possible in the past for cma_alloc() to take seconds or
longer to allocate, depending on the size of the CMA area and the
number of pinned GFP_MOVABLE pages within the CMA area.  Whether that
is true of today's CMA or not, I don't know.

It's probably there to allow such a situation to be recoverable, but
is not a good idea if we're expecting dma_alloc_*() not to fail in
those scenarios.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up