atomic operations in user space
DaveLiu at freescale.com
Tue Aug 29 20:05:24 EST 2006
> >>> 2) These mutexes are based on futexes which requires atomic
> >>> operations in userspace. These are available on most
> > Look at
> >>> the glibc code in
> >>> nptl/sysdeps/unix/sysv/linux/powerpc/lowlevellock.h for instance.
> >>> Use that and your PPC manual to implement your atomic operations.
> >> No matter semaphore or futex, it uses system calls to kernel.
> There is only a system call if there is congestion - that is
> the whole idea behind the futex.
> >> And the
> >> true atomic operation is in kernel not user space.
> "True" atomic operations are available in user space on most
> >> Maybe
> >> it's feasible
> >> for other architectures to do atomic operations directly in user
> >> space.
> >> IMHO, not for powerpc.
> It is available for PowerPC, but not in POWER and POWER2
> instructionsets according to
> It is the same in the ARM world: Atomic instructions was introduced in
> ARMv6 I believe. Older ARM processors don't have them.
> > Are you meaning that we didn't do atomic operations directly in user
> > space
> > on powerpc platform ?
> Well, that is not the conclusion I get either when reading
> the glibc code.
> Try to look at glibc-2.3.5/sysdeps/powerpc/bits/atomic.h.
> This is by the way probably what the original post in this
> thread wanted
> in the first place!
I totally agree with you and Brant about it. I don't believe we cannot
do the atomic operation in user space on powerpc.
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