Messages in this thread | | | Subject | Re: [PATCH] x86: fix and improve cmpxchg_double{,_local}() | From | Eric Dumazet <> | Date | Tue, 03 Jan 2012 16:15:14 +0100 |
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Le mardi 03 janvier 2012 à 16:00 +0100, Eric Dumazet a écrit :
> While looking at your patch, I discovered that atomic64_add() / > atomic64_inc() on 32bit are completely buggy. Oh well... > > Generated code : > > c03bc00c <atomic64_add_return_cx8>: > c03bc00c: 55 push %ebp > c03bc00d: 53 push %ebx > c03bc00e: 56 push %esi > c03bc00f: 57 push %edi > c03bc010: 89 c6 mov %eax,%esi > c03bc012: 89 d7 mov %edx,%edi > c03bc014: 89 cd mov %ecx,%ebp > c03bc016: 89 d8 mov %ebx,%eax > c03bc018: 89 ca mov %ecx,%edx > c03bc01a: f0 0f c7 4d 00 lock cmpxchg8b 0x0(%ebp) > c03bc01f: 89 c3 mov %eax,%ebx > c03bc021: 89 d1 mov %edx,%ecx > c03bc023: 01 f3 add %esi,%ebx > c03bc025: 11 f9 adc %edi,%ecx > c03bc027: f0 0f c7 4d 00 lock cmpxchg8b 0x0(%ebp) > c03bc02c: 75 f9 jne c03bc027 <atomic64_add_return_cx8+0x1b> > c03bc02e: 89 d8 mov %ebx,%eax > c03bc030: 89 ca mov %ecx,%edx > c03bc032: 5f pop %edi > c03bc033: 5e pop %esi > c03bc034: 5b pop %ebx > c03bc035: 5d pop %ebp > c03bc036: c3 ret > > The ' jne c03bc027' should really be 'jne c03bc01f' > > No idea how old is this bug. >
Very old it seems...
arch/x86/lib/atomic64_cx8_32.S
all "jxx 1b" are wrong if a LOCK_PREFIX is included after the 1: label
1: inst1 LOCK_PREFIX cmpxchg8b (%ebp) jne 1b / jumps to beginning of LOCK_PREFIX, inst1 is not replayed
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