fnf@estinc.UUCP (Fred Fish) (12/22/89)
Enclosed is a small test program that tickles a bug on our system. I'd
be curious to know if the same bug appears on other systems running SCO
Xenix 2.3.1, and if so, their configuration. Thanks!
======================================================================
/*
* This little program demonstrates a bug in the SCO tape driver for
* the following configuration. I don't know if it affects other
* configurations.
*
* Machine: Bell Technologies MPE with Bell supplied 60Mb tape
* SCO Release: 2.3.1
* Tape Config: Base addr = 0x300, Interrupt = 5, DMA = 1, Type = W
*
* Note that the Bell Tech supplied tape driver IS NOT used. The SCO
* driver is faster anyway...
*
* The bug is that if the tape is kept streaming, when it reaches the
* end of the tape, the first attempted write that fails returns with
* errno set to ENOSPC and subsequent tries fail and return with errno
* set to EIO. A close of the device then succeeds.
*
* However, if the tape is not kept streaming, the first failing write
* at the end of the tape returns with errno set to EIO, as do all
* subsequent writes. When the device is closed, the driver hangs
* (the drive light stays on and the system call never returns) until
* the tape is removed. The tape drive remains unusable until the
* system is rebooted. To demonstrate the bug, change the value of
* SLEEPTIME below to a large enough value to cause streaming to stop.
*
* This problem was discovered because unlike tar or cpio which give
* up and go home at the slightest hint of trouble, BRU wants to
* retry every failing archive I/O operation at least several times
* before attempting some other form of error recovery, such as deciding
* that the end of the tape has been reached and asking for the next one.
*
* - Fred Fish ><>
*
*/
#include <stdio.h>
#include <fcntl.h>
#define DEVICE "/dev/rct0" /* Device to test */
#define MAXERRORS 10 /* Maximum number of errors */
#define SLEEPTIME 5 /* 0 to stream, approx 5 for bug */
main ()
{
int fd;
int size = 0;
int errcount = 0;
char buf[1024 * 200];
if ((fd = open (DEVICE, O_WRONLY, 0666)) == -1) {
fprintf (stderr, "%s: can't open for write", DEVICE);
perror ("");
} else {
fprintf (stderr, "Writing device '%s', descriptor %d\n", DEVICE, fd);
fprintf (stderr, "Writing %d sized blocks\n", sizeof (buf));
fflush (stderr);
while (errcount < MAXERRORS) {
if (write (fd, buf, sizeof (buf)) == sizeof (buf)) {
size += sizeof (buf);
fprintf (stderr, "Wrote %dKb\n", size / 1024);
} else {
errcount++;
fprintf (stderr, "error %d (limit %d) ", errcount, MAXERRORS);
perror ("write failed");
}
fflush (stderr);
sleep (SLEEPTIME);
}
fprintf (stderr, "Close descriptor %d\n", fd);
if (close (fd) == -1) {
perror ("Close failed");
}
}
}
--
# Fred Fish, 1835 E. Belmont Drive, Tempe, AZ 85284, USA
# 1-602-491-0048 asuvax!{nud,mcdphx}!estinc!fnffnf@estinc.UUCP (Fred Fish) (12/23/89)
In article <250@estinc.UUCP> fnf@estinc.UUCP (Fred Fish) writes: > * ............... When the device is closed, the driver hangs > * (the drive light stays on and the system call never returns) until > * the tape is removed. The tape drive remains unusable until the > * system is rebooted. ....... Further investigation indicates that what I wrote here isn't totally true. The tape can be returned to service with the command "tape reset". -Fred -- # Fred Fish, 1835 E. Belmont Drive, Tempe, AZ 85284, USA # 1-602-491-0048 asuvax!{nud,mcdphx}!estinc!fnf