Date: Tue, 5 Apr 2016 13:42:20 -0400 (EDT)
From: Alan Stern <stern@rowland.harvard.edu>
To: Michal Nazarewicz <mina86@mina86.com>
cc: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>,
        Tony Lindgren <tony@atomide.com>, <linux-kernel@vger.kernel.org>,
        <linux-usb@vger.kernel.org>,
        Felipe Balbi <felipe.balbi@linux.intel.com>, Bin Liu <b-liu@ti.com>,
        <pali.rohar@gmail.com>
Subject: Re: [PATCH] usb: f_mass_storage: test whether thread is running
 before starting another
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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/multi¹ 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).
> 
> ¹ 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@mina86.com>

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