On Monday 15 May 2006 12:16, Tom Rini wrote: > On Mon, May 15, 2006 at 11:54:52AM -0500, Brent Cook wrote: > > The atomic operations in asm/atomic.h are really useful from userspace > > too. Other architectures (i386, x86_64, mips) export these to userspace, > > but the powerpc versions are guarded by __KERNEL__ for some reason. Can > > we remove these if there is no good reason to guard them? > > > > Signed-off-by: Brent Cook <bcook at bpointsys.com> > > NAK. i386, x86_64 and mips are broken in this regard. Please google up > the previous threads that explain why you can't always get atomic > operations on all architectures and why exporting this is bad.
OK, I see that possibly the only reason atomic_t is even exported is so that sem.h works. Hopefully sem.h will get fixed and people like me will not be even tempted by atomic.h. What I really want is just a standard way to do atomic inc/dec in userspace; I'm sure that people are going to continue wanting to have atomic_t workalikes for their code. After reading this thread: http://www.developerweb.net/forum/archive/index.php/t-3294.html it appears that just wrapping an integer in a pthreads mutex on an NPTL machine wouldn't be much more overhead than using an atomic_t directly. Looking at glibc's sources for powerpc nptl: nptl/sysdeps/unix/sysv/linux/powerpc/lowlevellock.h confirms that a futex lock is really similar to an atomic_t. Thanks! - Brent
