Re: [PATCHv2] usb: f_mass_storage: test whether thread is running before starting another

[Alan Stern]

On Fri, 8 Apr 2016, Michal Nazarewicz wrote:

> When binding the function to usb_configuration, check whether the thread
> is running before starting another one.  Without that, when function
> instance is added to multiple configurations, fsg_bing starts multiple
> threads with all but the latest one being forgotten by the driver.  This
> leads to obvious thread leaks, possible lockups when trying to halt the
> machine and possible more issues.
> 
> This fixes issues with legacy/multi gadget as well as configfs gadgets
> when mass_storage function is added to multiple configurations.
> 
> This change also simplifies API since the legacy gadgets no longer need
> to worry about starting the thread by themselves (which was where bug
> in legacy/multi was in the first place).
> 
> N.B., this patch doesnât address adding single mass_storage function
> instance to a single configuration twice.  Thankfully, thereâs no
> legitimate reason for such setup plus, if Iâm not mistaken, configfs
> gadget doesnât even allow it to be expressed.
> 
> Â I have no example failure though.  Conclusion that legacy/multi has
>   a bug is based purely on me reading the code.
> 
> Signed-off-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
> Tested-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@xxxxxxxxx>
> Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>