8056a75672
On Illumos callers of cv_timedwait and cv_timedwait_hires can't distinguish between whether or not the cv was signaled or the call timed out. Illumos handles this (for some definition of handles) by calling cv_signal in the return path if we were signaled but the return value indicates instead that we timed out. This would make sense if it were possible to query the the cv for its net signal disposition. However, this isn't possible and, in spite of the fact that there are places in the code that clearly take a different and incompatible path if a timeout value is indicated, this distinction appears to be rather subtle to most developers. This problem is further compounded by the fact that on Linux, calling cv_signal in the return path wouldn't even do the right thing unless there are other waiters. Since it is possible for the caller to independently determine how much time is remaining but it is not possible to query if the cv was in fact signaled, prioritizing signalling over timeout seems like a cleaner solution. In addition, judging from usage patterns within the code itself, it is also less error prone. Reviewed-by: Jorgen Lundman <lundman@lundman.net> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Alexander Motin <mav@FreeBSD.org> Signed-off-by: Matt Macy <mmacy@FreeBSD.org> Closes #10471 |
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