On Tue, Oct 16, 2012 at 1:36 AM, Juliusz Chroboczek <j...@pps.jussieu.fr> wrote:
> Hi,
>
> The Linux manual page for write(2) says:
>
> The adjustment of the file offset and the write operation are
> performed as an atomic step.
>
> This is apparently an extension to POSIX, which says
>
> This volume of IEEE Std 1003.1-2001 does not specify behavior of
> concurrent writes to a file from multiple processes. Applications
> should use some form of concurrency control.
>
> The following fragment of code
>
> int fd;
> fd = open("exemple", O_CREAT | O_WRONLY | O_TRUNC, 0666);
> fork();
> write(fd, "Ouille", 6);
You don't check return code here, does write succeed at all?
> close(fd);
>
> produces "OuilleOuille", as expected, on ext4 on two machines running
> Linux 3.2 AMD64. However, over XFS on an old Pentium III at 500 MHz
> running 2.6.32, it produces just "Ouille" roughly once in three times.
Does it ever produce e.g. OuOuilleille (as this is what atomicity is about
here)?
--
Thanks.
-- Max
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