Messages in this thread | | | Date | Fri, 4 Jul 2003 12:39:16 -0700 (PDT) | From | Davide Libenzi <> | Subject | Re: [PATCH 2.5.73] Signal stack fixes #1 introduce PF_SS_ACTIVE |
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On Fri, 4 Jul 2003, Linus Torvalds wrote:
> My reason for disliking this patch is that it adds user-space information > to the kernel - in a place where user space cannot get at it. > > In particular, any traditional cooperative user-space threading package > wants to switch its own stack around, and they all do it by just changing > %esp directly. The whole point of such threading is that it's _fast_, > since it doesn't need any kernel support (and since it's cooperative, you > can avoid locking). > > The old "optimization" that you didn't like was not an optimization at > all: it got the case of user space changing stacks _right_, while still > allowing yet another stack for signal handling and exiting the signal by > hand. > > Does anybody do that? I don't know. But it was done the way it was done on > purpose.
Yes, GNU Pth :
http://www.gnu.org/software/pth/
and, for example :
http://www.xmailserver.org/libpcl.html
They use the generic POSIX stack setup described here :
http://www.gnu.org/software/pth/rse-pmt.ps
My Pine's 'd' key deleted his patch before I could take an exhaustive look, but it should be fine though. They both do use to enter the signal handler simply to get a snapshot of the context, and they exit the handler by letting the kernel to clean the on-sig-stack flag. try to search archives to take a better look at the patch ...
- Davide
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