[Linux-ia64] static registers during a context switch

[Linux-ia64] static registers during a context switch

[riedel]

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hi everybody,
does anybody know what happens to static registers (gr0-gr31) in case of a context switch.
in the manual, it says static registers are visible to all procedures(i guess it shouldn't otherwise on a context switch another process would have the same static registers) On the other hand, stacked registers are local to procedures and saved and restored by RSE which makes sense to me.

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Re: [Linux-ia64] static registers during a context switch

[Doug Rabson]

On Tue, 24 Oct 2000, riedel wrote:

> hi everybody, does anybody know what happens to static registers
> (gr0-gr31) in case of a context switch. in the manual, it says static
> registers are visible to all procedures(i guess it shouldn't otherwise
> on a context switch another process would have the same static
> registers) On the other hand, stacked registers are local to
> procedures and saved and restored by RSE which makes sense to me.

Normally on a context switch, only the callee saved registers are
preserved (since the context switch appears as a function call to the
process which initiates it). In the case of ia64, this means that gr4-gr7
are preserved from the static register set.

-- 
Doug Rabson				Mail:  dfr@nlsystems.com
					Phone: +44 20 8348 6160

Re: [Linux-ia64] static registers during a context switch

[Don Dugger]

If you are thinking of a context switch in the sense of switching
from one process to another then ALL registers, static and stacked,
are saved and restored.  If you are talking about making a subroutine
call then the uses of the static registers are covered by software
convention and registers R4-R7 are preserved across a function call.

Conceptually the static registers are similar to the X86 registers
EAX, EBX and so on.  These registers are also saved and restored
across context switches and have software conventions that control
which ones are saved across subroutine calls.

On Tue, Oct 24, 2000 at 09:47:41PM -0500, riedel wrote:
> hi everybody,
> does anybody know what happens to static registers (gr0-gr31) in case of a context switch.
> in the manual, it says static registers are visible to all procedures(i guess it shouldn't otherwise on a context switch another process would have the same static registers) On the other hand, stacked registers are local to procedures and saved and restored by RSE which makes sense to me.

-- 
Don Dugger
"Censeo Toto nos in Kansa esse decisse." - D. Gale
n0ano@valinux.com
Ph: 303/938-9838