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Implementing TLS: step 1
- Subject: Implementing TLS: step 1
- From: eischen at vigrid.com (Daniel Eischen)
- Date: Fri Jun 20 13:46:09 2003
On Fri, 20 Jun 2003, Igor Sysoev wrote:
> I'm wrong, this scheme does not allow to use the 1:1 model in libkse
> when kse_mailbox.km_curthread is always NULL.
> We can implement such scheme on x86:
> gs -> [ TP ] ---> [ TLS ]
> [ struct kse_mailbox ] +-> [ struct kse_thr_mailbox ]
> [ .km_curthread ] -+
> When UTS would switch to the next thread it should set thread's TLS:
> kse_mailbox.km_curthread = NULL;
FYI, The above has to be atomic.
> gs: = next_thr_tls;
> kse_mailbox.km_curthread = next_kse_thr_mailbox;
FYI2, The above need not be atomic since upcalls are disabled
by the first line.
> kse_mailbox can be accessed via gs register. On amd64 scheme is the same
> except the use of fs register instead of gs.
> However on sparc64, ia64 and alpha TP is in the register but not
> in the memory so we need introduce the new field tm_kse in kse_thr_mailbox
> to find kse_mailbox:
> TP -> [ TLS ]
> [ struct kse_thr_mailbox ]
> [ .tm_kse ] ---> [ struct kse_mailbox ]
> By the way how was kse_mailbox being found before gs register was used ?
We've used %gs ever since we supported multiple KSEs.
Before, it was just a port of libc_r with everything
global and only 1 KSE.
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