forked from luck/tmp_suning_uos_patched
824975ef19
Linus noted (based on Eric Dumazet's numbers) that we would probably be better off not trying an atomic_read() in atomic64_add_return() but intead intentionally let the first cmpxchg8b fail - to get a cache-friendly 'give me ownership of this cacheline' transaction. That can then be followed by the real cmpxchg8b which sets the value local to the CPU. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> 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>
217 lines
4.5 KiB
C
217 lines
4.5 KiB
C
#include <linux/compiler.h>
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#include <linux/types.h>
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#include <asm/processor.h>
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#include <asm/cmpxchg.h>
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#include <asm/atomic.h>
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static inline u64 cmpxchg8b(u64 *ptr, u64 old, u64 new)
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{
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u32 low = new;
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u32 high = new >> 32;
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asm volatile(
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LOCK_PREFIX "cmpxchg8b %1\n"
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: "+A" (old), "+m" (*ptr)
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: "b" (low), "c" (high)
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);
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return old;
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}
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u64 atomic64_cmpxchg(atomic64_t *ptr, u64 old_val, u64 new_val)
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{
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return cmpxchg8b(&ptr->counter, old_val, new_val);
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}
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/**
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* atomic64_xchg - xchg atomic64 variable
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* @ptr: pointer to type atomic64_t
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* @new_val: value to assign
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*
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* Atomically xchgs the value of @ptr to @new_val and returns
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* the old value.
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*/
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u64 atomic64_xchg(atomic64_t *ptr, u64 new_val)
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{
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u64 old_val;
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do {
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old_val = atomic_read(ptr);
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} while (atomic64_cmpxchg(ptr, old_val, new_val) != old_val);
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return old_val;
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}
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/**
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* atomic64_set - set atomic64 variable
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* @ptr: pointer to type atomic64_t
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* @new_val: value to assign
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*
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* Atomically sets the value of @ptr to @new_val.
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*/
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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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/**
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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 old = 1LL << 32;
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return cmpxchg8b(&ptr->counter, old, old);
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}
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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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*
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* Atomically adds @delta to @ptr and returns @delta + *@ptr
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*/
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u64 atomic64_add_return(u64 delta, atomic64_t *ptr)
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{
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/*
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* Try first with a (probably incorrect) assumption about
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* what we have there. We'll do two loops most likely,
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* but we'll get an ownership MESI transaction straight away
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* instead of a read transaction followed by a
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* flush-for-ownership transaction:
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*/
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u64 old_val, new_val, real_val = 1ULL << 32;
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do {
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old_val = real_val;
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new_val = old_val + delta;
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real_val = atomic64_cmpxchg(ptr, old_val, new_val);
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} while (real_val != old_val);
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return new_val;
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}
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u64 atomic64_sub_return(u64 delta, atomic64_t *ptr)
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{
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return atomic64_add_return(-delta, ptr);
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}
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u64 atomic64_inc_return(atomic64_t *ptr)
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{
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return atomic64_add_return(1, ptr);
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}
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u64 atomic64_dec_return(atomic64_t *ptr)
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{
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return atomic64_sub_return(1, ptr);
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}
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/**
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* atomic64_add - add integer to atomic64 variable
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* @delta: integer value to add
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* @ptr: pointer to type atomic64_t
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*
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* Atomically adds @delta to @ptr.
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*/
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void atomic64_add(u64 delta, atomic64_t *ptr)
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{
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atomic64_add_return(delta, ptr);
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}
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/**
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* atomic64_sub - subtract the atomic64 variable
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* @delta: integer value to subtract
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* @ptr: pointer to type atomic64_t
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*
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* Atomically subtracts @delta from @ptr.
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*/
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void atomic64_sub(u64 delta, atomic64_t *ptr)
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{
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atomic64_add(-delta, ptr);
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}
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/**
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* atomic64_sub_and_test - subtract value from variable and test result
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* @delta: integer value to subtract
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* @ptr: pointer to type atomic64_t
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*
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* Atomically subtracts @delta from @ptr and returns
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* true if the result is zero, or false for all
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* other cases.
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*/
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int atomic64_sub_and_test(u64 delta, atomic64_t *ptr)
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{
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u64 old_val = atomic64_sub_return(delta, ptr);
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return old_val == 0;
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}
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/**
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* atomic64_inc - increment atomic64 variable
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* @ptr: pointer to type atomic64_t
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*
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* Atomically increments @ptr by 1.
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*/
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void atomic64_inc(atomic64_t *ptr)
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{
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atomic64_add(1, ptr);
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}
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/**
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* atomic64_dec - decrement atomic64 variable
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* @ptr: pointer to type atomic64_t
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*
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* Atomically decrements @ptr by 1.
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*/
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void atomic64_dec(atomic64_t *ptr)
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{
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atomic64_sub(1, ptr);
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}
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/**
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* atomic64_dec_and_test - decrement and test
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* @ptr: pointer to type atomic64_t
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*
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* Atomically decrements @ptr by 1 and
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* returns true if the result is 0, or false for all other
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* cases.
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*/
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int atomic64_dec_and_test(atomic64_t *ptr)
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{
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return atomic64_sub_and_test(1, ptr);
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}
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/**
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* atomic64_inc_and_test - increment and test
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* @ptr: pointer to type atomic64_t
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*
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* Atomically increments @ptr by 1
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* and returns true if the result is zero, or false for all
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* other cases.
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*/
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int atomic64_inc_and_test(atomic64_t *ptr)
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{
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return atomic64_sub_and_test(-1, ptr);
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}
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/**
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* atomic64_add_negative - add and test if negative
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* @delta: integer value to add
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* @ptr: pointer to type atomic64_t
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*
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* Atomically adds @delta to @ptr and returns true
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* if the result is negative, or false when
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* result is greater than or equal to zero.
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*/
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int atomic64_add_negative(u64 delta, atomic64_t *ptr)
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{
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long long old_val = atomic64_add_return(delta, ptr);
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return old_val < 0;
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}
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