Signals

[Doug Gwyn]

In article <1991Feb20.153845.14999 at b11.ingr.com> dclark at b11.ingr.com (Dave Clark) writes:
>When debugging a program recently, I found that it was crashing due to receipt
>of a signal "SIGEMT."  My manual describes this as:
>	SIGEMT		07	EMT instruction
>Naturally, "EMT" is not defined anywhere else in the manual.  Can someone out
>there in netland tell me what EMT stands for?  (Emergency Medical Technician
>is possible, but I can't figure out how one could get into the computer.)

EMT is a PDP-11 instruction meaning "EMulator Trap", intended to be used
to implement a form of system call and widely used for such in DEC's
PDP-11 operating systems.  (UNIX used the TRAP instruction instead.)

While some signals may be synchronously generated upon occurrence of
certain specific conditions during execution of a process, any signal
number may be asynchronously sent to a process via the kill() system
call.  Therefore a SIGEMT need not always imply that a PDP-11 EMT
instruction had been executed.