On Sun, Jul 14, 2013 at 9:17 PM, Andy Walls [off-list ref] wrote:

On Thu, 2013-07-11 at 17:05 +0800, Ming Lei wrote:

quoted

Hi,

As we are going to run URB->complete() in tasklet context[1][2],

Hi,

Please pardon my naivete, but why was it decided to use tasklets to
defer work, as opposed to some other deferred work mechanism?

It seems to me that getting rid of tasklets has been an objective for
years:

http://lwn.net/Articles/239633/
http://lwn.net/Articles/520076/
http://lwn.net/Articles/240054/

We discussed the problem in the below link previously[1], Steven
and Thomas suggested to use threaded irq handler, but which
may degrade USB mass storage performance, so we have to
take tasklet now until we rewrite transport part of USB mass storage
driver.

Also the conversion[2] has avoided the tasklet spin lock problem
already.


[1], http://marc.info/?t=137079119200001&r=1&w=2
[2], http://marc.info/?l=linux-usb&m=137286326726326&w=2


Thanks,
--
Ming Lei