Messages in this thread | | | Date | Thu, 5 Jul 2007 11:15:26 +0200 | From | Pavel Machek <> | Subject | removing refrigerator does not help with s2ram vs. fuse deadlocks (was Re: [linux-pm] Re: [PATCH] Remove process freezer from suspend to RAM pathway) |
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Hi!
> > The fact remains that lots of drivers would still need to be changed. > > In the read and write methods someone would have to add code amounting > > to this: > > > > if (suspend_is_under_way()) { > > mutex_unlock(...); > > block_until_resume(); > > goto restart; > > } > > > > Freezing userspace is a small amount of code by comparison. > > Normally devices have some sort of queue of pending operations. So > all that is required on suspend is to stop processing the queue and > wait for any currently-underway operations to complete. The blocking > then happens naturally using the normal I/O wait mechanisms.
So... instead of one big freezer (we know it is problematic), you have 100 small freezers, problematic in same way :-(.
Let's take current FUSE problems, and see if they have problem on PPC, ok?
Let's say FUSE thread touches one of those "blocking" devices. It is now in D state, somewhere in kernel.... exactly same way refrigerator works.
Now, if kernel needs FUSE services for some reason (that's the problem we hit in s2ram case, right?), we have a deadlock.
So main problem still seems to be "kernel should not depend on userland services during suspend", refrigerator or not. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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