On Mon, Aug 28, 2000 at 01:03:58PM -0400, Theodore Y. Ts'o wrote:
> Date: Sun, 27 Aug 2000 22:36:46 -0500 (CDT)
> From: Dave McCracken <dcm@mccr.org>
>
> I'll also admit signals were always a mess. They never fit very well
> with pthreads, and we pretty much punted in the early drafts. I
> added sigwait() to the original draft as a way an application could
> direct all its signal handling to a single synchronous 'signal
> handler' thread, but it never addressed the larger question of how to
> make signals and threads play together.
>
> I'll note that signals is one of the priamry places where Linuxthreads
> aren't compatible with Posix threads, and most of the various attempts
> to fix this involved kernel hacks that would have penelized the
> performance of the kernel in general, not just when dealing with Posix
> brain damage. (In one case, I believe the estimates were that it would
> slow signal delivery time by a factor of six.)
That must have been a particularly bad idea, the proposals were usually
in the range of a few ifs and 2-3 additional cache line references in
signal delivery.
[BTW, just by teaching all x86 glibcs to use sa_restorer properly you'll save
many more cycles than even a bad posix signal emulation could eat up --
-- the self modifying trampoline is deadly on modern CPUs]
> (And we haven't even gotten to pthread_cancel yet....)
That was unfair ;)
-Andi
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