Cyril Bur <cyril...@gmail.com> writes: > On Mon, 2017-07-17 at 19:29 +1000, Balbir Singh wrote: >> On Mon, 2017-07-17 at 17:55 +1000, Cyril Bur wrote: >> > On Mon, 2017-07-17 at 17:34 +1000, Balbir Singh wrote: >> > > On Wed, 2017-07-12 at 14:22 +1000, Cyril Bur wrote: >> > > > OPAL can only manage one flash access at a time and will return an >> > > > OPAL_BUSY error for each concurrent access to the flash. The simplest >> > > > way to prevent this from happening is with a mutex. >> > > > >> > > > Signed-off-by: Cyril Bur <cyril...@gmail.com> >> > > > --- >> > > >> > > Should the mutex_lock() be mutex_lock_interruptible()? Are we OK waiting >> > > on >> > > the mutex while other operations with the lock are busy? >> > > >> > >> > This is a good question. My best interpretation is that >> > _interruptible() should be used when you'll only be coming from a user >> > context. Which is mostly true for this driver, however, MTD does >> > provide kernel interfaces, so I was hesitant, there isn't a great deal >> > of use of _interruptible() in drivers/mtd. >> > >> > Thoughts? >> >> What are the kernel interfaces (I have not read through mtd in detail)? >> I would still like to see us not blocked in mutex_lock() across threads >> for parallel calls, one option is to use mutex_trylock() and return if >> someone already holds the mutex with -EBUSY, but you'll need to evaluate >> what that means for every call. > > Yeah maybe mutex_trylock() is the way to go, thinking quickly, I don't > see how it could be a problem for userspace using powernv_flash. I'm > honestly not too sure about the depths of the mtd kernel interfaces but > I've seen a tonne of cool stuff you could do, hence my reluctance to go > with _interruptible()
If you use trylock that means all your callers now need to handle EBUSY, which I doubt they do. Which means it goes up to userspace, which most users will just treat as a hard error. So that sounds like a bad plan to me. cheers
