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| -rw-r--r-- | man2/close.2 | 60 |
1 files changed, 31 insertions, 29 deletions
diff --git a/man2/close.2 b/man2/close.2 index a568534d31..121ca8de87 100644 --- a/man2/close.2 +++ b/man2/close.2 @@ -90,6 +90,37 @@ should not be retried after an error. POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD. .\" SVr4 documents an additional ENOLINK error condition. .SH NOTES +A successful close does not guarantee that the data has been successfully +saved to disk, as the kernel uses the buffer cache to defer writes. +Typically, filesystems do not flush buffers when a file is closed. +If you need to be sure that +the data is physically stored on the underlying disk, use +.BR fsync (2). +(It will depend on the disk hardware at this point.) +.PP +The close-on-exec file descriptor flag can be used to ensure +that a file descriptor is automatically closed upon a successful +.BR execve (2); +see +.BR fcntl (2) +for details. +.PP +It is probably unwise to close file descriptors while +they may be in use by system calls in +other threads in the same process. +Since a file descriptor may be reused, +there are some obscure race conditions +that may cause unintended side effects. +.\" Date: Tue, 4 Sep 2007 13:57:35 +0200 +.\" From: Fredrik Noring <noring@nocrew.org> +.\" One such race involves signals and ERESTARTSYS. If a file descriptor +.\" in use by a system call is closed and then reused by e.g. an +.\" independent open() in some unrelated thread, before the original system +.\" call has restarted after ERESTARTSYS, the original system call will +.\" later restart with the reused file descriptor. This is most likely a +.\" serious programming error. +.\" +.SS Dealing with error returns from close() A careful programmer will check the return value of .BR close (), since it is quite possible that errors on a previous @@ -200,35 +231,6 @@ the next major release of the POSIX.1 standard. .\" Review the following glibc bug later .\" https://sourceware.org/bugzilla/show_bug.cgi?id=14627 -A successful close does not guarantee that the data has been successfully -saved to disk, as the kernel uses the buffer cache to defer writes. -Typically, filesystems do not flush buffers when a file is closed. -If you need to be sure that -the data is physically stored on the underlying disk, use -.BR fsync (2). -(It will depend on the disk hardware at this point.) -.PP -The close-on-exec file descriptor flag can be used to ensure -that a file descriptor is automatically closed upon a successful -.BR execve (2); -see -.BR fcntl (2) -for details. -.PP -It is probably unwise to close file descriptors while -they may be in use by system calls in -other threads in the same process. -Since a file descriptor may be reused, -there are some obscure race conditions -that may cause unintended side effects. -.\" Date: Tue, 4 Sep 2007 13:57:35 +0200 -.\" From: Fredrik Noring <noring@nocrew.org> -.\" One such race involves signals and ERESTARTSYS. If a file descriptor -.\" in use by a system call is closed and then reused by e.g. an -.\" independent open() in some unrelated thread, before the original system -.\" call has restarted after ERESTARTSYS, the original system call will -.\" later restart with the reused file descriptor. This is most likely a -.\" serious programming error. .SH SEE ALSO .BR fcntl (2), .BR fsync (2), |