Abend 001

[robprins]

Hi,

During a file upload to UFS i met an abend 001. Probably an I/O error.
This will not happen every time. Most of the time the uploads run without problems.
See the attached dump.

Please advise,
Cheers, Rob

prt00f.zip

[mgrossmann]

Hi Rob,

Good news: the dump was all that was needed.

The abend is not in the UFS/upload path at all. It's a locking bug in libc370, the C runtime statically linked into FTPD: when two session threads write a log line at the same moment, the runtime's printf() loses its serialization mid-line, the two writes corrupt the shared stdout buffer, and the broken record hits the JES2 spool as an I/O error -- which MVS, lacking a SYNAD exit, turns into S001 and terminates the STC. Your dump actually shows the collision: the very last log record before the abend is two log lines merged into one truncated record. That's why it only happens occasionally, and preferably under parallel transfers.

Full analysis and fix tracking: mvslovers/libc370#145.

Since libc370 is statically linked into all our servers, the fix means new releases of UFSD, FTPD and HTTPD. This issue stays open until the fixed FTPD release is out.