Re: page busy vs. glock

[Juergen Hannken-Illjes <hannken%eis.cs.tu-bs.de@localhost>]

On Fri, Sep 05, 2008 at 07:29:04PM +0300, Antti Kantee wrote:
> Simon reported a problem where he's writing to a file (log of build -j4)
> and repeatedly doing tail -5000.  He says that this causes hangs sooner
> or later.
> 
> Upon examination, it seems that writing to the log goes through
> ufs_balloc_range(), which busies the new pages it wants to enlarge the
> file to and then takes the genfs node lock to do actual block allocation.
> 
> Meanwhile, tail coming in through mmap + genfs_getpages and holding the
> genfs lock tries to uvn_findpages.
>   ==> deadlock between PG_BUSY and glock

Is this deadlock really possible?
Do you have a stack trace?

-- 
Juergen Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig 
(Germany)