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Re: Decision time: Intel TSX Lock elision for glibc.
- From: Torvald Riegel <triegel at redhat dot com>
- To: "Carlos O'Donell" <carlos at redhat dot com>
- Cc: Andi Kleen <andi at firstfloor dot org>, libc-alpha at sourceware dot org, Rich Felker <dalias at aerifal dot cx>, Roland McGrath <roland at hack dot frob dot com>, Andreas Jaeger <aj at suse dot com>, "Joseph S. Myers" <joseph at codesourcery dot com>
- Date: Tue, 02 Jul 2013 12:54:07 +0200
- Subject: Re: Decision time: Intel TSX Lock elision for glibc.
- References: <1372452807-25216-1-git-send-email-andi at firstfloor dot org> <51D0A28F dot 4070409 at redhat dot com> <51D2121F dot 4020708 at redhat dot com>
On Mon, 2013-07-01 at 19:34 -0400, Carlos O'Donell wrote:
> * Patch 6 for elision of rwlocks is going to go to the Austin
> group to get clarification on what we perceive is an error
> in the language of the standard. If the wording is fixed then
> you won't be able to elide rwlock's since they will require
> deadlock on relock behaviour (the intention of the standard).
>From my point of view it would be fine to use elision just for rdlock
and tryrdlock, but *not* for wrlock or trywrlock. This would allow us
to use elision to avoid contention on the rwlock itself, even though we
couldn't use elision for write locks. But this would need a quick
change to the patch so that Carlos can review it again, and everyone
would need to be comfortable with this approach.
Torvald