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Re: TSX lock elision for glibc v12
- From: Rich Felker <dalias at aerifal dot cx>
- To: Andi Kleen <andi at firstfloor dot org>
- Cc: Torvald Riegel <triegel at redhat dot com>, libc-alpha at sourceware dot org, Carlos O'Donell <carlos at redhat dot com>, Roland McGrath <roland at hack dot frob dot com>
- Date: Fri, 21 Jun 2013 13:39:32 -0400
- Subject: Re: TSX lock elision for glibc v12
- References: <1371592286-22073-1-git-send-email-andi at firstfloor dot org> <1371753271 dot 964 dot 2220 dot camel at triegel dot csb> <20130621012328 dot GA29800 at brightrain dot aerifal dot cx> <1371811686 dot 964 dot 4100 dot camel at triegel dot csb> <1371823366 dot 964 dot 4706 dot camel at triegel dot csb> <1371824261 dot 964 dot 4757 dot camel at triegel dot csb> <1371826829 dot 964 dot 4905 dot camel at triegel dot csb> <20130621160924 dot GN6123 at two dot firstfloor dot org> <1371833629 dot 964 dot 5253 dot camel at triegel dot csb> <20130621172701 dot GO6123 at two dot firstfloor dot org>
On Fri, Jun 21, 2013 at 07:27:01PM +0200, Andi Kleen wrote:
> > I don't want to change or expose anything externally if I don't have to.
> > This will make it easier for us to just enable elision without risking
> > to have to maintain other interfaces, break ABIs, etc.
>
> I don't see the point of checking a new number on all the fast paths
> when it doesn't do anything different.
>
> With elision it's just the same as TIMED_NP | NO_ELISION
>
> So why not use that internally?
I agree. For now, pthread_mutexattr_settype can just set the "no
elision" flag whenever it's called. I don't see a need for a new mutex
type unless it would enable doing something that's actually useful.
Rich