netdev - Re: [PATCH 9/9] mmc: Convert from tasklet to BH workqueue

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: Thu, 28 Mar 2024 14:37:09 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Allen Pais <apais@...ux.microsoft.com>, linux-kernel@...r.kernel.org, tj@...nel.org, 
	keescook@...omium.org, vkoul@...nel.org, marcan@...can.st, sven@...npeter.dev, 
	florian.fainelli@...adcom.com, rjui@...adcom.com, sbranden@...adcom.com, 
	paul@...pouillou.net, Eugeniy.Paltsev@...opsys.com, 
	manivannan.sadhasivam@...aro.org, vireshk@...nel.org, Frank.Li@....com, 
	leoyang.li@....com, zw@...kernel.org, wangzhou1@...ilicon.com, 
	haijie1@...wei.com, shawnguo@...nel.org, s.hauer@...gutronix.de, 
	sean.wang@...iatek.com, matthias.bgg@...il.com, 
	angelogioacchino.delregno@...labora.com, afaerber@...e.de, 
	logang@...tatee.com, daniel@...que.org, haojian.zhuang@...il.com, 
	robert.jarzmik@...e.fr, andersson@...nel.org, konrad.dybcio@...aro.org, 
	orsonzhai@...il.com, baolin.wang@...ux.alibaba.com, zhang.lyra@...il.com, 
	patrice.chotard@...s.st.com, wens@...e.org, jernej.skrabec@...il.com, 
	peter.ujfalusi@...il.com, kys@...rosoft.com, haiyangz@...rosoft.com, 
	wei.liu@...nel.org, decui@...rosoft.com, jassisinghbrar@...il.com, 
	mchehab@...nel.org, maintainers@...echerrydvr.com, 
	aubin.constans@...rochip.com, manuel.lauss@...il.com, mirq-linux@...e.qmqm.pl, 
	jh80.chung@...sung.com, oakad@...oo.com, hayashi.kunihiko@...ionext.com, 
	mhiramat@...nel.org, brucechang@....com.tw, HaraldWelte@...tech.com, 
	pierre@...man.eu, duncan.sands@...e.fr, stern@...land.harvard.edu, 
	oneukum@...e.com, openipmi-developer@...ts.sourceforge.net, 
	dmaengine@...r.kernel.org, asahi@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, linux-rpi-kernel@...ts.infradead.org, 
	linux-mips@...r.kernel.org, imx@...ts.linux.dev, 
	linuxppc-dev@...ts.ozlabs.org, linux-mediatek@...ts.infradead.org, 
	linux-actions@...ts.infradead.org, linux-arm-msm@...r.kernel.org, 
	linux-riscv@...ts.infradead.org, linux-sunxi@...ts.linux.dev, 
	linux-tegra@...r.kernel.org, linux-hyperv@...r.kernel.org, 
	linux-rdma@...r.kernel.org, linux-media@...r.kernel.org, 
	linux-mmc@...r.kernel.org, linux-omap@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, linux-s390@...r.kernel.org, 
	netdev@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH 9/9] mmc: Convert from tasklet to BH workqueue

On Thu, Mar 28, 2024 at 1:54 PM Ulf Hansson <ulf.hansson@...aro.org> wrote:

> At this point we have suggested to drivers to switch to use threaded
> irq handlers (and regular work queues if needed too). That said,
> what's the benefit of using the BH work queue?

Context:
https://lwn.net/Articles/960041/
"Tasklets, in particular, remain because they offer lower latency than
workqueues which, since they must go through the CPU scheduler,
can take longer to execute a deferred-work item."

The BH WQ is controlled by a software IRQ and quicker than an
ordinary work item.

I don't know if this little latency could actually affect any MMC
device, I doubt it.

The other benefit IIUC is that it is easy to mechanically rewrite tasklets
to BH workqueues and be sure that it is as fast as the tasklet, if you want
to switch to threaded IRQ handlers or proper work, you need to write a
lot of elaborate code and test it (preferably on real hardware).

Yours,
Linus Walleij