d599e4fa79
Previously we would ASSERT in cv_destroy() if it was ever called with active waiters. However, I've now seen several instances in OpenSolaris code where they do the following: cv_broadcast(); cv_destroy(); This leaves no time for active waiters to be woken up and scheduled and we trip the ASSERT. This has not been observed to be an issue on OpenSolaris because their cv_destroy() basically does nothing. They still do run the risk of the memory being free'd after the cv_destroy() and hitting a bad paging request. But in practice this race is so small and unlikely it either doesn't happen, or is so unlikely when it does happen the root cause has not yet been identified. Rather than risk the same issue in our code this change updates cv_destroy() to block until all waiters have been woken and scheduled. This may take some time because each waiter must acquire the mutex. This change may have an impact on performance for frequently created and destroyed condition variables. That however is a price worth paying it avoid crashing your system. If performance issues are observed they can be addressed by the caller.
The Solaris Porting Layer (SPL) is a Linux kernel module which provides many of the Solaris kernel APIs. This shim layer makes it possible to run Solaris kernel code in the Linux kernel with relatively minimal modification. This can be particularly useful when you want to track upstream Solaris development closely and don’t want the overhead of maintaining a large patch which converts Solaris primitives to Linux primitives.
To build packages for your distribution:
$ ./configure
$ make pkg
Full documentation for building, configuring, and using the SPL can be found at: http://zfsonlinux.org