David S. Miller wrote:
From: Mark A Smith <[EMAIL PROTECTED]>
Date: Mon, 15 May 2006 14:39:06 -0700
I discovered that in some cases, send(), sendmsg(), and sendto() are not
thread-safe. Although the man page for these functions does not specify
whether these functions are supposed to be thread-safe, my reading of the
POSIX/SUSv3 specification tells me that they should be. I traced the
problem to tcp_sendmsg(). I was very curious about this issue, so I wrote
up a small page to describe in more detail my findings. You can find it at:
http://www.almaden.ibm.com/cs/people/marksmith/sendmsg.html .
# ./sendmsgclient localhost
ERROR! We should have all 0! We don't!
buff[16384]=1
buff[16385]=1
buff[16386]=1
buff[16387]=1
buff[16388]=1
buff[16389]=1
buff[16390]=1
buff[16391]=1
buff[16392]=1
buff[16393]=1
That's 10/32768 bad bytes
# uname -a
HP-UX tarry B.11.23 U ia64 2397028692 unlimited-user license
Given that the URL above asserts that HP-UX claims atomicity, either
there is a bug in the UX stack, or perhaps the test? I took a quick
look at the HP-UX 11iv2 (aka 11.23) manpage for sendmsg and didn't see
anything about atomicity there - on which manpage(s) or docs was the
assertion of HP-UX atomicity made?
I presume this is only for "blocking" sockets? I cannot at least off
the top of my head see how a stack could offer it on non-blocking sockets.
And frankly, BSD defines BSD socket semantics here not some wording in
the POSIX standards.
Have BSD socket semantics ever been updated/clarified any any
quasi-official manner since the popular presence of threads? Or
are/were Posix/Xopen filling a gap?
rick jones
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