x86: atomic64: Inline atomic64_read() again
Now atomic64_read() is light weight (no register pressure and small icache), we can inline it again. Also use "=&A" constraint instead of "+A" to avoid warning about unitialized 'res' variable. (gcc had to force 0 in eax/edx) $ size vmlinux.prev vmlinux.after text data bss dec hex filename 4908667 451676 1684868 7045211 6b805b vmlinux.prev 4908651 451676 1684868 7045195 6b804b vmlinux.after Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Cc: 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: <4A4E1AA2.30002@gmail.com> [ Also fix typo in atomic64_set() export ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
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@ -295,6 +295,28 @@ extern void atomic64_set(atomic64_t *ptr, u64 new_val);
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*
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* Atomically reads the value of @ptr and returns it.
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*/
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static inline u64 atomic64_read(atomic64_t *ptr)
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{
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u64 res;
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/*
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* Note, we inline this atomic64_t primitive because
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* it only clobbers EAX/EDX and leaves the others
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* untouched. We also (somewhat subtly) rely on the
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* fact that cmpxchg8b returns the current 64-bit value
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* of the memory location we are touching:
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*/
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asm volatile(
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"mov %%ebx, %%eax\n\t"
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"mov %%ecx, %%edx\n\t"
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LOCK_PREFIX "cmpxchg8b %1\n"
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: "=&A" (res)
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: "m" (*ptr)
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);
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return res;
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}
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extern u64 atomic64_read(atomic64_t *ptr);
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/**
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@ -66,31 +66,10 @@ void atomic64_set(atomic64_t *ptr, u64 new_val)
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{
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atomic64_xchg(ptr, new_val);
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}
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EXPORT_SYMBOL(atomic64_read);
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EXPORT_SYMBOL(atomic64_set);
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/**
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* atomic64_read - read atomic64 variable
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* @ptr: pointer to type atomic64_t
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*
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* Atomically reads the value of @ptr and returns it.
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*/
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u64 atomic64_read(atomic64_t *ptr)
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{
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u64 res;
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asm volatile(
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"mov %%ebx, %%eax\n\t"
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"mov %%ecx, %%edx\n\t"
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LOCK_PREFIX "cmpxchg8b %1\n"
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: "+A" (res)
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: "m" (*ptr)
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);
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return res;
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}
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EXPORT_SYMBOL(atomic64_read);
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/**
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* atomic64_add_return - add and return
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* @delta: integer value to add
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* @ptr: pointer to type atomic64_t
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