Re: [PATCH v11 04/14] s390/zcrypt: driver callback to indicate resource in use

[Halil Pasic]

On Fri, 13 Nov 2020 16:30:31 -0500
Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote:

> We will be using the mutex_trylock() function in our sysfs 
> assignment
> interfaces which make the call to the AP bus to check permissions (which 
> also
> locks ap_perms). If the mutex_trylock() fails, we return from the assignment
> function with -EBUSY. This should resolve that potential deadlock issue.

It resolves the deadlock issue only if in_use() is also doing
mutex_trylock(), but the if in_use doesn't take the lock it
needs to back off (and so does it's client code) i.e. a boolean as
return value won't do.

Regards,
Halil