Re: close() of active socket does not work on FreeBSD 6

On Thu, 21 Dec 2006, Robert Watson wrote:

On Wed, 20 Dec 2006, Julian Elischer wrote:

I think the main concern is if we will record every thread using a fd, that means, when you call read() on a fd, you record your thread pointer into the fd's thread list, when one wants to close the fd, it has to notify all the threads in the list, set a flag for each thread, the flag indicates a thread is interrupted because the fd was closed, when the thread returns from deep code path to read() syscall, it should check the flag, and return EBADF to user if it was set. whatever, a reserved signal or TDF_INTERRUPT may interrupt a thread. but since there are many file operations, I don't know if we are willing to pay such overheads to every file syscall, extra locking is not welcomed.

I think you are only intersted in treads that are sleeping.. so you allow a sleeping thread to save a pointer to the fd (or whatever) on which it is sleeping, along with the sleep address.

items that are not sleeping are either already returning, or are going to sleep, in which case they can check at that time.

Hence my question about select and poll: should they throw an exception state when a file descriptor is closed out from under them? They often sleep on hundreds or thousands of file descriptors, and not just one.

Yes, I would think so. Solaris behaves this way also, although
there seems to be a bug in Solaris 8 (version tested) in that
select() returns -1 but errno isn't properly set (it is 0).

--
DE
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Relevant Pages

  • Re: close() of active socket does not work on FreeBSD 6
    ... means, when you call readon a fd, you record your thread pointer into the fd's thread list, when one wants to close the fd, it has to notify all the threads in the list, set a flag for each thread, the flag indicates a thread is interrupted because the fd was closed, when the thread returns from deep code path to readsyscall, it should check the flag, and return EBADF to user if it was set. ... I think you are only intersted in treads that are sleeping.. ... so you allow a sleeping thread to save a pointer to the fd on which it is sleeping, ... when a file descriptor is closed out from under them? ...
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