Change VERIFY to ASSERT in mutex_destroy()

[behlendorf]

There have been multiple reports of 'zdb' tripping the VERIFY in
mutex_destroy() because pthread_mutex_destroy() returns EBUSY.

Exactly how this can happen still needs to be explained, but this
doesn't strictly need to be fatal for non-debug builds. Therefore,
this patch converts the VERIFY to an ASSERT until the root cause
is determined and resolved.

Signed-off-by: Brian Behlendorf behlendorf1@llnl.gov
Issue #2027

[ryao]

@behlendorf The reason people are using zdb in #2027 is to access vdev GUIDs. That suffers from problems where GUIDs on cache devices are not shown and it is a pain to access. Furthermore, zdb is a developer tool that should remain as such. We should merge #2012 to address the needs of users before we implement a workaround so that they can continue using zdb as a hack.

[behlendorf]

@ryao we should definitely merge #2012, and I don't think there's anything holding that up now. But that shouldn't prevent us from merging this. Changing this to as ASSERT won't be harmful to users, and developers should already be typically running with ASSERTS enable so no change there. That said, I'd rather get to the root cause of this but at least we can minimize the trouble is causes.

[behlendorf]

340dfbe Change VERIFY to ASSERT in mutex_destroy()