I have many processes running via LSF and trying to read and write the same file. I have used flock everywhere, LOCK_SH for reads and LOCK_EX for writes. This usually works. But every now and then I get a failure. 
open LOGFILE, ">>$logfile" or die("can't open");
flock(LOGFILE, LOCK_EX) or die("can't lock ($!)")

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gives me "can't lock (Input/output error)". I can't reproduce this in a simple test case. My simple test cases always work. Any idea what would cause flock to fail in this way? What does "Input/output error" from a flock failure mean?

In reply to flock "Input/output error" by Anonymous Monk

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