6 minute delay on mutex_exit?

Question

I'm seeing some very odd behavior on mutex_exit(). The man page gives the impression that calling mutex_exit() will schedule another process that might be waiting on that mutex, and that's fine, for the purposes of my driver. When I added some timing code, however, I noticed that mutex_exit() sometimes takes a very, very long time to complete.
Here's my debug code (pretty straightforward stuff):
     hrtime_t start1, end;
     start1 = gethrtime();
     mutex_exit(&ctlr->lock);
     end1 = gethrtime();
     if(end1 - start1 > (NANOSEC)) {     /* 1 sec */
          cmn_err(CE_WARN, "mutex_exit took %u ms", (end1 - start1)/1000000);
Here's the message that prints out when the odd behavior occurs:
mutex_exit took 386565 ms
The system is continuing to function (apparently normally) during this time. Anybody ever see anything like this? Any ideas about what it might be?

Answer 1

hrtime_t is a 64-bit "long long" type, but you print the 64-bit expression "(end1 - start1)/1000000" using a
32-bit unsigned format.
What happens when you change the cmn_err to use a 64-bit format?
cmn_err(CE_WARN, "mutex_exit took %llu ms", (end1 - start1)/1000000);