:I'm trying to write some experimental mutex operations similar to those
:in -current, but to do differnt things (e.g. a read/write lock)
:however, I am having some problems with the __asm stuff.
:
:What I want to do is to define some operations that will
:assemble down to:
: pushfl
: cli
: [stuff]
: popfl
:
:I can generate the code, but it seems to me that there should be
:a way of telling gcc that you have just pushed an item onto the stack,
:so that if you were to have some C code between the push and po
:(of the flags reg) the compiler has a correct idea of where the
:SP is. I can imagine that it doesn't matter so it may be that there
:is no constaint for that purpose (I read the gcc asm info pages)
:but I wanted to make sure that that is the case because if it does turn
:out to be important, it may manifest itself as a wierd bug sometime
:in 2002.
:
:The current pushfl code in the kernel has the following:
: __asm __volatile("pushfl; popl %0" : "=r" (ef));
:which has no long term effect on the stack pointer so I cannot
:use it as a guide.
:
:--
: __--_|\ Julian Elischer
I think all you can do is move the addresses and data used
by 'stuff' into registers prior to the push, then manipulate
the registers between the push and the pop.
-Matt
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