[PATCH 15/15] Add DEFINE_SPUFS_ATTRIBUTE()
michael at ellerman.id.au
Thu Sep 13 12:05:41 EST 2007
On Wed, 2007-09-12 at 10:47 +0200, Arnd Bergmann wrote:
> On Wednesday 12 September 2007, Michael Ellerman wrote:
> > On Wed, 2007-09-12 at 17:43 +1000, Michael Ellerman wrote:
> > > This patch adds DEFINE_SPUFS_ATTRIBUTE(), a wraper around
> > > DEFINE_SIMPLE_ATTRIBUTE which does the specified locking for the get
> > > routine for us.
> > >
> > > Unfortunately we need two get routines (a locked and unlocked version) to
> > > support the coredump code. This patch hides one of those (the locked version)
> > > inside the macro foo.
> > jk said:
> > > "Good god man!"
> > Yeah, I'm a bit lukewarm on this one. But the diffstat is nice, 50% code
> > reduction ain't bad :)
> Have you looked at the change in object code size? I would expect the
> object code to actually become bigger. I also think that it hurts
> readability rather than help it.
Yeah I did, it's smaller actually:
text data bss dec hex filename
44898 17804 120 62822 f566 spufs-before.o
44886 17804 120 62810 f55a spufs-after.o
> Maybe a better solution is to change the core dump code to not
> require the mutex to be held in the first place. By the time
> we get to call the get functions, it should already be in
> saved state and no longer be able to get scheduled, so we might
> not actually need all the extra tricks with avoiding the
> mutex to be taken again.
Well that'd be nice, but I don't see anywhere that that happens. AFAICT
the acquire we do in the first coredump callback is the first the SPU
contexts know about their PPE process dying. And spufs is still live, so
I think we definitely need to grab the mutex, or we might race with
userspace accessing spufs files.
OzLabs, IBM Australia Development Lab
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