Attachment 11304 Details for Bug 11381 – Patch for 4.2 cherry-picked from master

[patch] Patch for 4.2 cherry-picked from master

42-tbd-dealock.patch (text/plain), 1.92 KB, created by Ralph Böhme on 2015-08-03 13:08:37 UTC

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Creator: Ralph Böhme

Created: 2015-08-03 13:08:37 UTC

Size: 1.92 KB

patch

obsolete

>From ff8d4157e611053c70120cb57692827dd31a5024 Mon Sep 17 00:00:00 2001
>From: Volker Lendecke <vl@samba.org>
>Date: Mon, 6 Jul 2015 13:13:36 +0200
>Subject: [PATCH] tdb: Fix bug 11381, deadlock
>
>This fixes a deadlock in tdb that is a bad interaction between tdb_lockall
>and tdb_traverse. This deadlock condition has been around even before
>tdb mutexes, it's just that the kernel fcntl EDEADLK detection protected
>us from this ABBA lock condition to become a real deadlock stalling
>processes. With tdb mutexes, this deadlock protection is gone, so we do
>lock dead.
>
>This patch glosses over this particular ABBA condition, making tdb with
>mutexes behave the same as tdb without mutexes. Admittedly this is no
>real fix, but it works around a real user's problem.
>
>Bug: https://bugzilla.samba.org/show_bug.cgi?id=11381
>Signed-off-by: Volker Lendecke <vl@samba.org>
>Reviewed-by: Jeremy Allison <jra@samba.org>
>(cherry picked from commit 1061a9cafda7d73ebcd2f74e69e74f4adc485d5d)
>---
> lib/tdb/common/traverse.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
>diff --git a/lib/tdb/common/traverse.c b/lib/tdb/common/traverse.c
>index 618670f..e18e3c3 100644
>--- a/lib/tdb/common/traverse.c
>+++ b/lib/tdb/common/traverse.c
>@@ -245,13 +245,25 @@ _PUBLIC_ int tdb_traverse(struct tdb_context *tdb,
> 		 tdb_traverse_func fn, void *private_data)
> {
> 	struct tdb_traverse_lock tl = { NULL, 0, 0, F_WRLCK };
>+	enum tdb_lock_flags lock_flags;
> 	int ret;
> 
> 	if (tdb->read_only || tdb->traverse_read) {
> 		return tdb_traverse_read(tdb, fn, private_data);
> 	}
> 
>-	if (tdb_transaction_lock(tdb, F_WRLCK, TDB_LOCK_WAIT)) {
>+	lock_flags = TDB_LOCK_WAIT;
>+
>+	if (tdb->allrecord_lock.count != 0) {
>+		/*
>+		 * This avoids a deadlock between tdb_lockall() and
>+		 * tdb_traverse(). See
>+		 * https://bugzilla.samba.org/show_bug.cgi?id=11381
>+		 */
>+		lock_flags = TDB_LOCK_NOWAIT;
>+	}
>+
>+	if (tdb_transaction_lock(tdb, F_WRLCK, lock_flags)) {
> 		return -1;
> 	}
> 
>-- 
>2.1.0
>

Flags:

jra: review+
vl: review+

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Attachments on bug 11381: 11229 | 11230 | 11231 | 11234 | 11235 | 11304