tree ffc1f1795b9e156ce54f3f9d8915730d1c60635a
parent dc39455e7948ec9bc5f3f2dced5c2f5ac8a8dfd9
author Kyle McMartin <kyle@shortfin.cabal.ca> 1204395952 -0800
committer Kyle McMartin <kyle@shortfin.cabal.ca> 1205633537 -0700

[PARISC] futex: special case cmpxchg NULL in kernel space

Commit a0c1e9073ef7428a14309cba010633a6cd6719ea added code to futex.c
to detect whether futex_atomic_cmpxchg_inatomic was implemented at run
time:

+       curval = cmpxchg_futex_value_locked(NULL, 0, 0);
+       if (curval == -EFAULT)
+               futex_cmpxchg_enabled = 1;

This is bogus on parisc, since page zero in kernel virtual space is the
gateway page for syscall entry, and should not be read from the kernel.
(That, and we really don't like the kernel faulting on its own address
 space...)

Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>