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Date: Thu, 4 Feb 2010 00:43:35 +0100
Message-ID: <4e6cba831002031543r391ba4c7m620868fe9cc044a8@mail.gmail.com>
From: Giovanni Trematerra <giovanni.trematerra@gmail.com>
To: Brandon Gooch <jamesbrandongooch@gmail.com>
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Cc: Attilio Rao <attilio@freebsd.org>,
FreeBSD Current <freebsd-current@freebsd.org>,
Randall Stewart <rrs@lakerest.net>
Subject: Re: A strange thing with yesterday's head..
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> Just tried it again (a few times) at r203430, with similar results.
Hi Brandon,
did you update -STABLE? I meant -CURRENT!
Anyway, if you are updating -STABLE, please try the patch below. I
don't know if it applies on -STABLE, let me know.
Thanks for your time.
--
Gianni
--- head/sys/kern/kern_umtx.c 2010/01/10 09:31:57 201991
+++ head/sys/kern/kern_umtx.c 2010/02/03 03:56:32 203414
@@ -2526,6 +2526,12 @@
umtxq_busy(&uq->uq_key);
umtxq_unlock(&uq->uq_key);
+ /*
+ * re-read the state, in case it changed between the try-lock above
+ * and the check below
+ */
+ state = fuword32(__DEVOLATILE(int32_t *, &rwlock->rw_state));
+
/* set read contention bit */
while ((state & wrflags) && !(state & URWLOCK_READ_WAITERS)) {
oldstate = casuword32(&rwlock->rw_state, state, state |
URWLOCK_READ_WAITERS);
@@ -2658,6 +2664,12 @@
umtxq_busy(&uq->uq_key);
umtxq_unlock(&uq->uq_key);
+ /*
+ * re-read the state, in case it changed between the try-lock above
+ * and the check below
+ */
+ state = fuword32(__DEVOLATILE(int32_t *, &rwlock->rw_state));
+
while (((state & URWLOCK_WRITE_OWNER) || URWLOCK_READER_COUNT(state) != 0) &&
(state & URWLOCK_WRITE_WAITERS) == 0) {
oldstate = casuword32(&rwlock->rw_state, state, state |
URWLOCK_WRITE_WAITERS);