yield() and cond_resched() do not yield to another thread

yield() and cond_resched() do not yield to another thread

[fei phung]

Hi everyone,

I am working on https://github.com/promach/riffa/tree/full_duplex

While I modifying the linux driver, I faced some issue using yield().

Why riffa_driver.c yield() function
https://gist.github.com/promach/7716ee8addcaa33fda140d74d1ad94d6#file-riffa_driver-c-L746

does not yield to chnl_send() thread
https://gist.github.com/promach/7716ee8addcaa33fda140d74d1ad94d6#file-riffa_driver-c-L883
?

See https://stackoverflow.com/questions/52166325/why-yield-and-cond-resched-do-not-yield-to-another-thread
for more details
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Re: yield() and cond_resched() do not yield to another thread

[Stephen Hemminger]

On Tue, 4 Sep 2018 21:16:07 +0800
fei phung <feiphung27@gmail.com> wrote:

> Hi everyone,
> 
> I am working on https://github.com/promach/riffa/tree/full_duplex
> 
> While I modifying the linux driver, I faced some issue using yield().
> 
> Why riffa_driver.c yield() function
> https://gist.github.com/promach/7716ee8addcaa33fda140d74d1ad94d6#file-riffa_driver-c-L746
> 
> does not yield to chnl_send() thread
> https://gist.github.com/promach/7716ee8addcaa33fda140d74d1ad94d6#file-riffa_driver-c-L883
> ?
> 
> See https://stackoverflow.com/questions/52166325/why-yield-and-cond-resched-do-not-yield-to-another-thread
> for more details
> _______________________________________________
> devel mailing list
> devel@linuxdriverproject.org
> http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel

Using yield in modern code is almost always wrong. It has priority inversion and latency
issues. You are much better off using a real syncronization primitive (like completion or wait).
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Re: yield() and cond_resched() do not yield to another thread

[Stephen Hemminger]

On Tue, 4 Sep 2018 21:16:07 +0800
fei phung <feiphung27@gmail.com> wrote:

> Hi everyone,
> 
> I am working on https://github.com/promach/riffa/tree/full_duplex
> 
> While I modifying the linux driver, I faced some issue using yield().
> 
> Why riffa_driver.c yield() function
> https://gist.github.com/promach/7716ee8addcaa33fda140d74d1ad94d6#file-riffa_driver-c-L746
> 
> does not yield to chnl_send() thread
> https://gist.github.com/promach/7716ee8addcaa33fda140d74d1ad94d6#file-riffa_driver-c-L883
> ?
> 
> See https://stackoverflow.com/questions/52166325/why-yield-and-cond-resched-do-not-yield-to-another-thread
> for more details
> _______________________________________________
> devel mailing list
> devel@linuxdriverproject.org
> http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel

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