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[Bug translator/10741] Merge tandem locks
- From: "fche at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: systemtap at sources dot redhat dot com
- Date: 20 Nov 2009 19:43:33 -0000
- Subject: [Bug translator/10741] Merge tandem locks
- References: <20091006202043.10741.jistone@redhat.com>
- Reply-to: sourceware-bugzilla at sourceware dot org
------- Additional Comments From fche at redhat dot com 2009-11-20 19:43 -------
archiving irc yak on topic:
fche anyway, I was thinking that another locking-related optimization could be
done by escalating read-to-write locks within probe handlers, suchly:
fche global foo probe bar { if (foo) { foo++ } }
fche so the idea would be to initially read-lock foo, and only later upgrade it
to a write-lock
fche the theory being that some / many (??) probes start with some condition
checking, and some (???) of that time, a write does not actually end up happening
jistone hmm
jistone have to think about whether that could induce any lock inversion
fche oh yeah, lots of complications
fche just wanted to brain-dump here FWIW
jistone probe foo { if (++a) ++b } probe bar { if (++b) ++a } global a,b
jistone does the initial read lock solve that? I think it might...
--
http://sourceware.org/bugzilla/show_bug.cgi?id=10741
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