send(), sendmsg(), sendto() not thread-safe

[Mark A Smith <mark1smi@us.ibm.com>]

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 .

Thanks,
Mark A. Smith

PS. I am using the term "thread" in the general sense, this is a problem
independent of pthreads, etc. The problem occurs when two processes
(whether or not they share an address space) send on the same socket (and
some other low-resource conditions exist).

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