Differential D7462 Diff 19304 lib/libc/sys/aio_mlock.2

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lib/libc/sys/aio_mlock.2

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	.Pp			.Pp
	If the request could not be enqueued (generally due to			If the request could not be enqueued (generally due to
	.Xr aio 4			.Xr aio 4
	limits),			limits),
	then the call returns without having enqueued the request.			then the call returns without having enqueued the request.
	.Pp			.Pp
	The			The
	.Fa iocb->aio_sigevent			.Fa iocb->aio_sigevent
	structure can be used to request notification of the request's			structure can be used to request notification of the operation's
	completion as described in			completion as described in
	.Xr aio 4 .			.Xr aio 4 .
	.Sh RESTRICTIONS			.Sh RESTRICTIONS
	The Asynchronous I/O Control Block structure pointed to by			The Asynchronous I/O Control Block structure pointed to by
	.Fa iocb			.Fa iocb
	and the buffer that the			and the buffer that the
	.Fa iocb->aio_buf			.Fa iocb->aio_buf
	member of that structure references must remain valid until the			member of that structure references must remain valid until the
	operation has completed.			operation has completed.
	For this reason, use of auto (stack) variables
	for these objects is discouraged.
	.Pp			.Pp
	The asynchronous I/O control buffer			The asynchronous I/O control buffer
	.Fa iocb			.Fa iocb
	should be zeroed before the			should be zeroed before the
	.Fn aio_mlock			.Fn aio_mlock
	call to avoid passing bogus context information to the kernel.			call to avoid passing bogus context information to the kernel.
	.Pp			.Pp
	Modifications of the Asynchronous I/O Control Block structure or the			Modifications of the Asynchronous I/O Control Block structure or the
	buffer contents after the request has been enqueued, but before the			memory mapping described by the virtual address range are not allowed
	request has completed, are not allowed.			while the request is queued.
				jhbAuthorUnsubmitted Not Done Inline Actions In this case, I didn't want to keep the prohibition on modifying the buffer (i.e. the memory mapped by the region being mlock'd) as modifying the data in the pages won't result in indeterminate behavior wrt mlock(). However, it's not clear if we should prohibit changes to the mapping (e.g. munmap(), mprotect(), etc.) while the request is pending? jhb: In this case, I didn't want to keep the prohibition on modifying the buffer (i.e. the memory…
				kibUnsubmitted Not Done Inline Actions We should prohibit changes to mappings, since mappings are parsed at the moment the mlock() is performed. Or rather, the aio request would mlock whatever is mapped at the time of processing, rather at the time of issuing the request. BTW, there is a difference between modifying buffers or mappings, and modifying the control block itself. The laguage above only talks about control block. kib: We should prohibit changes to mappings, since mappings are parsed at the moment the mlock() is…
	.Sh RETURN VALUES			.Sh RETURN VALUES
	.Rv -std aio_mlock			.Rv -std aio_mlock
	.Sh ERRORS			.Sh ERRORS
	The			The
	.Fn aio_mlock			.Fn aio_mlock
	system call will fail if:			system call will fail if:
	.Bl -tag -width Er			.Bl -tag -width Er
	.It Bq Er EAGAIN			.It Bq Er EAGAIN
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