Rational VADS 6.2.3a & Solaris signals

Rational VADS 6.2.3a & Solaris signals

[George Rice]

I'm having a problem with UNIX signals. I have a set of processes 
running on a SPARCstation under Solaris 2.4. The programs are written
in Ada using the Rational VADS 6.2.3a runtime environment. I am 
simulating a hardware environment and need to simulate bus interrupts 
between the processes.

I have written Ada bindings to the sigsend system service and each
process has a signal handler attached to the sigusr1 unix signal. 
To simulate the hardware interrupt, I use the Ada binding to send 
the sigusr1 signal to the other processes. In general, this system 
works but has the following problems:

  1) I randomly see a Pending Kernel Service Queue Overflow error from 
the Rational runtime. It is my understanding that this is due to too 
many system service calls being queued while processing a signal. 
However, all the signal handler does is use the vads_exec library 
service to set a semaphore which another task is waiting on. The handler 
then goes back to waiting for the next signal. Our design is such that 
another signal will not be sent until all processes have indicated that 
the current signal has been serviced. I have increased the size of the 
pending kernel service queue via the Pending_Count parameter in the user 
configuration file but this did not help.

  2) I also randomly see a missed signal. The signal sender blocks until 
all processes have serviced the interrupt. Occasionally our system hangs 
with the sender waiting on one process which has not received the 
signal. The sigsend to that process did not return an error yet the 
signal was apparently not received. By manually sending the sigusr1 
signal to the process from an xterm, I can jumpstart the system and 
execution continues.

  3) Also, the overhead associated with using signals seems to be 
excessive, about 1 ms per signal. Previously we were using the Verdix 
2.1.1 runtime and the signal overhead was worse by about a factor of 10. 
It improved to where it is now when we went to the Rational 6.2.3a 
runtime. I don't know if this can by improved further or not.

  Has anyone out there had similar experiences? I welcome all comments 
and suggestions.

                             Sean.A.Corcoran@lmtas.lmco.com

-- 
(posted for Sean by:)
George F. Rice                  817-763-4216 (voice)  817-762-1444 (fax)
George.F.Rice@lmtas.lmco.com          http://webmmc.lmtas.lmco.com/~rice
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