Messages in this thread | | | Date | Thu, 4 May 2006 09:39:53 -0700 (PDT) | From | Vadim Lobanov <> | Subject | Re: limits / PIPE_BUF? |
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On Thu, 4 May 2006, Arjan van de Ven wrote:
> On Wed, 2006-05-03 at 22:55 -0700, Vadim Lobanov wrote: > > A snippet from include/linux/limits.h: > > #define PIPE_BUF 4096 /* # bytes in atomic write to a pipe */ > > > > PIPE_BUF is a bit of an oddity. It is defined there, then redefined in > > the arm header files, even though those header files are never included > > anywhere. Also, PIPE_BUF is never referenced by name in any of the Linux > > code. And yet, it is still being mentioned in some Big And Scary > > Warnings (tm): fs/autofs4/waitq.c or include/linux/pipe_fs_i.h, for > > example. > > it's for userland to tell it what the size of the atomic pipe operations > we can do is. >
How does userland get this value from the kernel? How does the kernel code ensure that this value is honored, considering that PIPE_BUF is not referenced in any of the pipe code?
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