Two fixes for sys_rwlock #5907
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Two fixes for sys_rwlock #5907
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kd-11
approved these changes
May 3, 2019
readers can wait on the sleep queue if a writer lock has been blocked before it, in this case after runlock: writer should acquire the lock but the r's sleep queue is still not empty!
If the rwlock is currently acquired by a writer signaling readers is wrong and will lead to EPERM for wunlock! Only signal blocked readers if the rwlock is currently acquired by readers
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Looks like you added another fix, doesn't that make it three fixes now? |
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Both regarding readers blocked because theres a writer on the sleep queue.
First fix: fix signaling bit when ownership passed to a writer, yet there are still readers waiting on the sleep queue.
Second fix: Do not signal readers while the lock is still acquired by a writer when the last writer on the sleep queue quits.