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socket: Add macros to lock socket buffers using socket references
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Authored by markj on Fri, Sep 10, 4:19 PM.

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Summary

Since commit c67f3b8b78e50c6df7c057d6cf108e4d6b4312d0 the sockbuf
mutexes belong to the containing socket. Sockbufs contain a pointer to
a mutex, which by default is initialized to the corresponding mutexes in
the socket. The SOCKBUF_LOCK() etc. macros operate on this pointer.
However, the pointer is clobbered by listen(2) so it's not safe to use
them unless one is sure that the socket is not a listening socket.

This change introduces a new set of macros which lock socket buffers
through the socket. This is a bit cheaper since it removes the pointer
indirection, and allows one to safely lock socket buffers and then check
for a listening socket.

I have some changes staged which convert most consumers to use the new
macros, though this introduces a fair bit of churn. The new locking
macros can be trivially implemented in terms of the existing ones on
stable/13, though, so I don't think it's a major problem to do the sweep
and MFC.

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R10 FreeBSD src repository
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Event Timeline

markj requested review of this revision.Fri, Sep 10, 4:19 PM
This revision is now accepted and ready to land.Fri, Sep 10, 6:50 PM

It's almost (but not really) tempting to name then SND and RCV similar to the so_rcv/so_snd fields. Having the extra 'E' for readability is probably an improvement though.

In D31900#719868, @jhb wrote:

It's almost (but not really) tempting to name then SND and RCV similar to the so_rcv/so_snd fields. Having the extra 'E' for readability is probably an improvement though.

... and I already used SEND/RECV in the macros which replace sblock().