Gleb Natapov wrote: > On Tue, Mar 06, 2007 at 11:24:06AM +0100, Bert Wesarg wrote: >> Hello, >> >> Gleb Natapov wrote: >>> If it does this after opal_atomic_lock() (which is explicit memory >>> barrier) then it is broken. >> Than, gcc 4.1.1 on the amd64 architecture is broken: > And can you repeat the test please, but make "test" variable to be global > to tell compiler that it can be actually accessed by more then one > thread. >
ahh, now both produce nearly the same code. but who hurts it to declare the variable volatile? Bert
--- double_check.s 2007-03-06 12:07:12.103478512 +0100 +++ double_check_volatile.s 2007-03-06 12:06:20.675315485 +0100 @@ -1,4 +1,4 @@ - .file "double_check.c" + .file "double_check_volatile.c" .text .p2align 4,,15 .globl main @@ -13,8 +13,9 @@ # first if #NO_APP - decl %eax + movl test(%rip), %eax movl $1, %edx + decl %eax je .L4 #APP # lock @@ -43,7 +44,8 @@ # second if #NO_APP - cmpl $1, test(%rip) + movl test(%rip), %eax + decl %eax jne .L8 #APP # if unlock
