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.\" 2008-10-10, mtk: describe eventfd2(), and EFD_NONBLOCK and EFD_CLOEXEC
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.TH EVENTFD 2 2009-01-26 Linux "Linux Programmer's Manual"
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.TH EVENTFD 2 2010-08-30 Linux "Linux Programmer's Manual"
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eventfd \- create a file descriptor for event notification
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This counter is initialized with the value specified in the argument
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Starting with Linux 2.6.27, the following values may be bitwise ORed in
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The following values may be bitwise ORed in
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to change the behaviour of
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file status flag on the new open file description.
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Using this flag saves extra calls to
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to achieve the same result.
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.BR EFD_CLOEXEC " (since Linux 2.6.27)"
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Set the close-on-exec
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flag on the new file descriptor.
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for reasons why this may be useful.
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.BR EFD_NONBLOCK " (since Linux 2.6.27)"
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file status flag on the new open file description.
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Using this flag saves extra calls to
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to achieve the same result.
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.BR EFD_SEMAPHORE " (since Linux 2.6.30)"
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Provide semaphore-like semantics for reads from the new file descriptor.
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In Linux up to version 2.6.26, the
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The following operations can be performed on the file descriptor:
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If the eventfd counter has a nonzero value, then a
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returns an 8-byte integer.
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will fail with the error
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if the size of the supplied buffer is less than 8 bytes.
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is in host byte order,
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i.e., the native byte order for integers on the host machine.
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depend on whether the eventfd counter currently has a nonzero value
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flag was specified when creating the eventfd file descriptor:
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was not specified and the eventfd counter has a nonzero value, then a
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returns 8 bytes containing that value,
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and the counter's value is reset to zero.
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(The returned value is in host byte order,
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i.e., the native byte order for integers on the host machine.)
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If the counter is zero at the time of the
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was specified and the eventfd counter has a nonzero value, then a
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returns 8 bytes containing the value 1,
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and the counter's value is decremented by 1.
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If the eventfd counter is zero at the time of the call to
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then the call either blocks until the counter becomes nonzero,
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then the call either blocks until the counter becomes nonzero
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proceeds as described above)
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or fails with the error
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if the file descriptor has been made nonblocking.
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will fail with the error
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if the size of the supplied buffer is less than 8 bytes.
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man2/eventfd.2
