[PATCH] macintosh: Explicitly set llseek to no_llseek in ans-lcd
fweisbec at gmail.com
Thu Oct 22 09:16:21 EST 2009
On Wed, Oct 21, 2009 at 11:53:21PM +0200, John Kacur wrote:
> > No problem with that. Setting no_llseek or generic_file_llseek_unlocked,
> > depending on the context is the right thing to do.
> > What I'm wondering about concerns the future code that will have
> > no llsek() implemented in their fops.
> > We can't continue to use default_llseek() for future code unless we
> > want to continue these post reviews and fixes forever.
> I'm thinking that the simplier approach, would be to make the
> default_llseek the unlocked one. Then you only have to audit the drivers
> that have the BKL - ie the ones we are auditing anyway, and explicitly set
> them to the bkl locked llseek.
> There might be a hidden interaction though between the non-unlocked
> variety of ioctls and default llseek though.
I fear that won't work because the bkl in default_llseek() does not
only synchronizes with others uses of the bkl in a driver, it also
synchronizes lseek() itself.
As an example offset change is not atomic. This is a long long, so
updating its value is not atomic in 32 bits archs.
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