The generic atomic64_t implementation in lib/ did not export the functions
it defined, which means that modules that use atomic64_t would not link on
platforms (such as 32-bit powerpc). For example, trying to build a kernel
with CONFIG_NET_RDS on such a platform would fail with:
ERROR: "atomic64_read" [net/rds/rds.ko] undefined!
ERROR: "atomic64_set" [net/rds/rds.ko] undefined!
Fix this by exporting the atomic64_t functions to modules. (I export the
entire API even if it's not all currently used by in-tree modules to avoid
having to continue fixing this in dribs and drabs)
Signed-off-by: Roland Dreier <rolandd@cisco.com>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Many processor architectures have no 64-bit atomic instructions, but
we need atomic64_t in order to support the perf_counter subsystem.
This adds an implementation of 64-bit atomic operations using hashed
spinlocks to provide atomicity. For each atomic operation, the address
of the atomic64_t variable is hashed to an index into an array of 16
spinlocks. That spinlock is taken (with interrupts disabled) around the
operation, which can then be coded non-atomically within the lock.
On UP, all the spinlock manipulation goes away and we simply disable
interrupts around each operation. In fact gcc eliminates the whole
atomic64_lock variable as well.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
