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From: Alan Cox <>
To: Linus Torvalds <>
	Linux Kernel Mailing List <>
Subject: Re: Make pipe data structure be a circular list of pages, rather
Date: Sat, 08 Jan 2005 21:47:05 +0000	[thread overview]
Message-ID: <1105216050.10519.64.camel@localhost.localdomain> (raw)
In-Reply-To: <>

On Sad, 2005-01-08 at 18:41, Linus Torvalds wrote:
> For all of those that are valid (certainly the signal case), you need to
> put the pipe into nonblocking mode anyway, so I don't think coalescing is
> really needed. SuS certainly does _not_ seem guarantee that you can do
> many nonblocking writes (small _or_ big). Let's see if somebody reports 
> any trouble with the new world order.

It breaks netscape 3 if I simulate it (but thats picking an app I know
makes silly assumptions).

>From the rules pasted below I think the 1 byte at a time 4K write is
guaranteed or at least strongly implied. The single write atomicity is
guaranteed but that is if anything made easier by the changes.

(From pathconf)


             returns  the  size of the pipe buffer, where filedes must
              to a pipe or FIFO and path must refer to  a  FIFO.  The 
              sponding macro is _POSIX_PIPE_BUF.

(From pwrite)

Write requests of {PIPE_BUF} bytes or less shall not be interleaved with
data from other processes doing writes on the same pipe. Writes of
greater than {PIPE_BUF} bytes may have data interleaved, on arbitrary
boundaries, with writes by other processes, whether or not the
O_NONBLOCK flag of the file status flags is set.

[of O_NDELAY for pipe]
A write request for {PIPE_BUF} or fewer bytes shall have the following
effect: if there is sufficient space available in the pipe, write()
shall transfer all the data and return the number of bytes requested.
Otherwise, write() shall transfer no data and return -1 with errno set
to [EAGAIN].

  reply	other threads:[~2005-01-08 22:51 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-01-08  8:25 Make pipe data structure be a circular list of pages, rather linux
2005-01-08 18:41 ` Linus Torvalds
2005-01-08 21:47   ` Alan Cox [this message]
2005-01-13 21:46   ` Ingo Oeser
2005-01-13 22:32     ` Linus Torvalds
2005-01-14 21:03       ` Ingo Oeser
2005-01-14 21:29         ` Linus Torvalds
2005-01-14 22:12           ` Ingo Oeser
2005-01-14 22:44             ` Linus Torvalds
2005-01-14 23:34               ` Ingo Oeser
2005-01-15  0:16                 ` Linus Torvalds
2005-01-16  2:59                   ` Linus Torvalds
2005-01-17 16:03                     ` Ingo Oeser
2005-01-19 21:12                     ` Make pipe data structure be a circular list of pages, rather than linux
2005-01-20  2:06                       ` Robert White
2005-01-15 23:42 Make pipe data structure be a circular list of pages, rather linux
2005-01-15 22:55 ` Alan Cox
2005-01-16  0:12   ` Linus Torvalds
2005-01-16  2:02     ` Miquel van Smoorenburg
2005-01-16  2:06     ` Jeff Garzik

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