On 2014-05-06 08:48:57 -0400, Robert Haas wrote:
> On Tue, May 6, 2014 at 8:43 AM, Andres Freund <and...@2ndquadrant.com> wrote:
> > The break because of refcnt == 1 doesn't generally seem to be a good
> > idea. Why are we bailing if there's *any* segment that's in the process
> > of being removed? I think the check should be there *after* the
> > dsm_control->item[i].handle == seg->handle check?
>
> You are correct. Good catch.
Fix attached.
Greetings,
Andres Freund
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Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
>From 9bc05ac103c77fcd2276754a3ccbf49e66dd00b7 Mon Sep 17 00:00:00 2001
From: Andres Freund <and...@anarazel.de>
Date: Tue, 6 May 2014 19:08:07 +0200
Subject: [PATCH] Don't bail in dsm_attach() if any any other segment is about
to be destroyed.
The previous coding accidentally checked for refcnt == 1, which
signals moribund segments, before checking whether the segment we're
looking at is the one we're trying to attach to.
---
src/backend/storage/ipc/dsm.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/src/backend/storage/ipc/dsm.c b/src/backend/storage/ipc/dsm.c
index d86b0c7..bde7026 100644
--- a/src/backend/storage/ipc/dsm.c
+++ b/src/backend/storage/ipc/dsm.c
@@ -570,6 +570,10 @@ dsm_attach(dsm_handle h)
if (dsm_control->item[i].refcnt == 0)
continue;
+ /* Not the segment you're looking for. */
+ if (dsm_control->item[i].handle != seg->handle)
+ continue;
+
/*
* If the reference count is 1, the slot is still in use, but the
* segment is in the process of going away. Treat that as if we
@@ -578,13 +582,10 @@ dsm_attach(dsm_handle h)
if (dsm_control->item[i].refcnt == 1)
break;
- /* Otherwise, if the descriptor matches, we've found a match. */
- if (dsm_control->item[i].handle == seg->handle)
- {
- dsm_control->item[i].refcnt++;
- seg->control_slot = i;
- break;
- }
+ /* Otherwise we've found a match. */
+ dsm_control->item[i].refcnt++;
+ seg->control_slot = i;
+ break;
}
LWLockRelease(DynamicSharedMemoryControlLock);
--
1.8.5.rc2.dirty
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