mirror of https://gitee.com/openkylin/linux.git
locking: Remove atomicy checks from {READ,WRITE}_ONCE
The fact that volatile allows for atomic load/stores is a special case not a requirement for {READ,WRITE}_ONCE(). Their primary purpose is to force the compiler to emit load/stores _once_. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com> Acked-by: Will Deacon <will.deacon@arm.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Paul McKenney <paulmck@linux.vnet.ibm.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -192,29 +192,16 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
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#include <uapi/linux/types.h>
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#include <uapi/linux/types.h>
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static __always_inline void data_access_exceeds_word_size(void)
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#ifdef __compiletime_warning
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__compiletime_warning("data access exceeds word size and won't be atomic")
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#endif
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;
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static __always_inline void data_access_exceeds_word_size(void)
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{
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}
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static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
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static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
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{
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{
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switch (size) {
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switch (size) {
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case 1: *(__u8 *)res = *(volatile __u8 *)p; break;
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case 1: *(__u8 *)res = *(volatile __u8 *)p; break;
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case 2: *(__u16 *)res = *(volatile __u16 *)p; break;
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case 2: *(__u16 *)res = *(volatile __u16 *)p; break;
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case 4: *(__u32 *)res = *(volatile __u32 *)p; break;
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case 4: *(__u32 *)res = *(volatile __u32 *)p; break;
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#ifdef CONFIG_64BIT
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case 8: *(__u64 *)res = *(volatile __u64 *)p; break;
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case 8: *(__u64 *)res = *(volatile __u64 *)p; break;
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#endif
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default:
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default:
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barrier();
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barrier();
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__builtin_memcpy((void *)res, (const void *)p, size);
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__builtin_memcpy((void *)res, (const void *)p, size);
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data_access_exceeds_word_size();
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barrier();
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barrier();
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}
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}
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}
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}
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@ -225,13 +212,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
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case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
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case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
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case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
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case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
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case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
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case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
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#ifdef CONFIG_64BIT
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case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
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case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
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#endif
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default:
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default:
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barrier();
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barrier();
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__builtin_memcpy((void *)p, (const void *)res, size);
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__builtin_memcpy((void *)p, (const void *)res, size);
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data_access_exceeds_word_size();
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barrier();
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barrier();
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}
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}
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}
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}
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