Rather than the detail of SPLICE_F_NONBLOCK getting long, move this to its own section where it can grow to include the information with greater clarity. Added a description of the behaviour against a blocking file descriptor, including an important gotcha. I have aimed to keep to the section headings specified in man-pages(7). The description that "splice() may nevertheless block because the file descriptors that are spliced to/from may block" remains although I did not observe or investigate this behaviour myself. --- man2/splice.2 | 47 ++++++++++++++++++++++++++++++++++++++++------- 1 files changed, 40 insertions(+), 7 deletions(-) diff --git a/man2/splice.2 b/man2/splice.2 index 035aac4..cf1e2f6 100644 --- a/man2/splice.2 +++ b/man2/splice.2 @@ -105,13 +105,11 @@ call); in the future, a correct implementation may be restored. .TP .B SPLICE_F_NONBLOCK -Do not block on I/O. -This makes the splice pipe operations nonblocking, but -.BR splice () -may nevertheless block because the file descriptors that -are spliced to/from may block (unless they have the -.B O_NONBLOCK -flag set). +Make the splice operation itself nonblocking. See the +.B NOTES +on +.B Nonblocking behaviours +below. .TP .B SPLICE_F_MORE More data will be coming in a subsequent splice. @@ -184,6 +182,41 @@ library support was added to glibc in version 2.5. .SH CONFORMING TO This system call is Linux-specific. .SH NOTES +.SS Nonblocking behaviours +Whether +.BR splice () +may block is influenced by the +.B O_NONBLOCK +flag on +.I fd_in +and +.IR fd_out , +and the +.B SPLICE_F_NONBLOCK +flag. + +Without +.B SPLICE_F_NONBLOCK +the behaviour of the underlying +file descriptors defines when the +.BR splice() +operation will block. + +If +.B SPLICE_F_NONBLOCK +is set then the movement of data within +.BR splice() +is unblocking. +However, +.BR splice() +may nevertheless block because the file descriptors that +are spliced to/from may block. +Care should be taken with this flag as +.BR splice() +will not block if data from a blocking file descriptor is not resident +in memory; there can be a difference in behaviour where file +content is or is not already cached to RAM. +.SS Related calls The three system calls .BR splice (), .BR vmsplice (2), -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
