aacf682fd8
Linus noticed that the 32-bit version of atomic64_read() was being overly complex with re-reading the value and doing a retry loop over that. Instead we can just rely on cmpxchg8b returning either the new value or returning the current value. We can use any 'old' value, which will be faster as it can be loaded via immediates. Using some value that is not equal to the real value in memory the instruction gets faster. This also has the advantage that the CPU could avoid dirtying the cacheline. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: David Howells <dhowells@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Arnd Bergmann <arnd@arndb.de> LKML-Reference: <alpine.LFD.2.01.0907021653030.3210@localhost.localdomain> Signed-off-by: Ingo Molnar <mingo@elte.hu> |
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| .. | ||
| atomic64_32.c | ||
| checksum_32.S | ||
| clear_page_64.S | ||
| copy_page_64.S | ||
| copy_user_64.S | ||
| copy_user_nocache_64.S | ||
| csum-copy_64.S | ||
| csum-partial_64.c | ||
| csum-wrappers_64.c | ||
| delay.c | ||
| getuser.S | ||
| io_64.c | ||
| iomap_copy_64.S | ||
| Makefile | ||
| memcpy_32.c | ||
| memcpy_64.S | ||
| memmove_64.c | ||
| memset_64.S | ||
| mmx_32.c | ||
| msr.c | ||
| putuser.S | ||
| rwlock_64.S | ||
| semaphore_32.S | ||
| string_32.c | ||
| strstr_32.c | ||
| thunk_32.S | ||
| thunk_64.S | ||
| usercopy_32.c | ||
| usercopy_64.c | ||