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authorPaul Mackerras <paulus@samba.org>2009-06-12 17:10:05 -0400
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2009-06-14 23:27:38 -0400
commit09d4e0edd4614e787393acc582ac701c6ec3565b (patch)
tree77f3b85e0f59a168ac78639e510ebcbd3791b3d2 /lib/Kconfig
parent4c75f84f2c781beb230031234ed961d28771a764 (diff)
lib: Provide generic atomic64_t implementation
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>
Diffstat (limited to 'lib/Kconfig')
-rw-r--r--lib/Kconfig6
1 files changed, 6 insertions, 0 deletions
diff --git a/lib/Kconfig b/lib/Kconfig
index 9960be04cbbe..bb1326d3839c 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -194,4 +194,10 @@ config DISABLE_OBSOLETE_CPUMASK_FUNCTIONS
194config NLATTR 194config NLATTR
195 bool 195 bool
196 196
197#
198# Generic 64-bit atomic support is selected if needed
199#
200config GENERIC_ATOMIC64
201 bool
202
197endmenu 203endmenu