On Tue, 29 Aug 2006, Liu Dave-r63238 wrote:
>>> 2) These mutexes are based on futexes which requires atomic >>> operations in userspace. These are available on most architectures. > 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 architectures. >> 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 http://www.nersc.gov/vendor_docs/ibm/asm/lwarx.htm#idx607 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! Esben > -DAve > _______________________________________________ > Linuxppc-embedded mailing list > Linuxppc-embedded at ozlabs.org > https://ozlabs.org/mailman/listinfo/linuxppc-embedded >
