Re: [patch] SMP alternatives
From: Eric W. Biederman
Date: Wed Nov 23 2005 - 18:31:04 EST
Linus Torvalds <torvalds@xxxxxxxx> writes:
> On Wed, 23 Nov 2005, H. Peter Anvin wrote:
>> Yes. Any shared mmaps may require working lock.
> Not "any". Only writable shared mmap. Which is actually the rare case.
> Even then, we might want to have such processes have a way to say "I don't
> do futexes in this mmap" or similar. Quite often, writable shared mmaps
> aren't interested in locked cycles - they are there to just write things
> to disk, and all the serialization is done in the kernel when the user
> does a "munmap()" or a "msync()".
In fact for being explict we already have PROT_SEM on some architectures
to report if we are going to use atomic operations, in the mmap. For
x86 we would probably need to introduce a PROT_NOSEM but it is sounds
fairly straight forward to implement.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/