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| author | Paul Mackerras <paulus@samba.org> | 2009-06-12 21:10:05 +0000 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2009-06-15 13:27:38 +1000 |
| commit | 09d4e0edd4614e787393acc582ac701c6ec3565b (patch) | |
| tree | 77f3b85e0f59a168ac78639e510ebcbd3791b3d2 /lib/Kconfig | |
| parent | 4c75f84f2c781beb230031234ed961d28771a764 (diff) | |
| download | lwn-09d4e0edd4614e787393acc582ac701c6ec3565b.tar.gz lwn-09d4e0edd4614e787393acc582ac701c6ec3565b.zip | |
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/Kconfig | 6 |
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 config NLATTR bool +# +# Generic 64-bit atomic support is selected if needed +# +config GENERIC_ATOMIC64 + bool + endmenu |