058de03caa
For debugging purposes the condition varaibles keep track of the mutex used during a wait. The idea is to validate that all callers always use the same mutex. Unfortunately, we have seen cases where the caller reuses the condition variable with a different mutex but in a way which is known to be safe. My reading of the man pages suggests you should not do this and always cv_destroy()/cv_init() a new mutex. However, there is overhead in doing this and it does appear to be allowed under Solaris. To accomidate this behavior cv_wait_common() and __cv_timedwait() have been modified to clear the associated mutex when the last waiter is dropped. This ensures that while the condition variable is in use the incorrect mutex case is detected. It also allows the condition variable to be safely recycled without requiring the overhead of a cv_destroy()/cv_init() as long as it isn't currently in use. Finally, spin lock cv->cv_lock was removed because it is not required. When the condition variable is used properly the caller will always be holding the mutex so the spin lock is redundant. The lock was originally added because I expected to need to protect more than just the cv->cv_mutex. It turns out that was not the case. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> |
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