On 02/22/2012 04:50 PM, Roland McGrath wrote:

On Wed, Feb 22, 2012 at 4:29 PM, H. Peter Anvin [off-list ref] wrote:

quoted

Can we really introduce force-kill semantics for a POSIX-defined signal?
Other user space programs might use it for other purposes.

The semantics are based on how the signal was generated, not what signal
number it was.  The only thing that depends on the signal number is
SYNCHRONOUS_MASK, which just determines in which order pending signals are
dequeued (POSIX says it may be any order).  We only have that so your state
doesn't get unhelpfully warped to another signal handler entry point
(including fiddling the stack) before you dump core.

No use of SIGSYS is specified by POSIX at all, of course, since "system
call" is an implementation concept below the level POSIX specifies.

I meant whether or not a signal can be blocked/caught and the fact that
the signal exists at all.

Now I guess we could have "blockable" and "unblockable" SIGSYS, but that
would seem to have its own set of issues...

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.