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

From: Alan Stern
Date: Tue Apr 05 2016 - 13:42:29 EST


On Tue, 5 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).
>
> 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>

This doesn't address the problem I raised in a previous email.
Sharing one thread among several function instances in the same config
will not work if one of them encounters an error.

Alan Stern