From f4ca3de8c6a25bb4ea052450f5dd6aec62070939 Mon Sep 17 00:00:00 2001
From: "benjamin.franksen" <benjamin.franksen@helmholtz-berlin.de>
Date: Thu, 1 Mar 2012 13:57:35 +0000
Subject: [PATCH] seq: fixed order of state set wakeup and signalling of
completions
This was a subtle concurrency bug discovered and analyzed by Lewis Muir:
if pvPutComplete or pvGetComplete are used inside a when-clause, waking
up the state set before signalling completion could result in a deadlock.
---
src/seq/seq_ca.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/src/seq/seq_ca.c b/src/seq/seq_ca.c
index 4ebdf24f..2acc6361 100644
--- a/src/seq/seq_ca.c
+++ b/src/seq/seq_ca.c
@@ -253,14 +253,6 @@ static void proc_db_events(
ss_write_buffer(ch, val, &meta, evtype == MON_COMPLETE);
}
- /* Wake up each state set that uses this channel in an event */
- seqWakeup(sp, ch->eventNum);
-
- /* If there's an event flag associated with this channel, set it */
- /* TODO: check if correct/documented to do this for non-monitor completions */
- if (ch->efId > 0)
- seq_efSet(sp->ss, ch->efId);
-
/* Signal completion */
switch (evtype)
{
@@ -273,6 +265,14 @@ static void proc_db_events(
default:
break;
}
+
+ /* If there's an event flag associated with this channel, set it */
+ /* TODO: check if correct/documented to do this for non-monitor completions */
+ if (ch->efId > 0)
+ seq_efSet(sp->ss, ch->efId);
+
+ /* Wake up each state set that uses this channel in an event */
+ seqWakeup(sp, ch->eventNum);
}
struct putq_cp_arg {
--
GitLab