Bug 13021 - GET_DB_SEQNUM control can cause ctdb to deadlock when databases are frozen
Summary: GET_DB_SEQNUM control can cause ctdb to deadlock when databases are frozen
Status: RESOLVED FIXED
Alias: None
Product: Samba 4.1 and newer
Classification: Unclassified
Component: CTDB (show other bugs)
Version: 4.6.7
Hardware: All All
: P5 major (vote)
Target Milestone: ---
Assignee: Karolin Seeger
QA Contact: Samba QA Contact
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2017-09-08 01:04 UTC by Amitay Isaacs
Modified: 2017-09-14 14:12 UTC (History)
3 users (show)

See Also:

Attachments
Patches for v4-6 (3.38 KB, patch)
2017-09-13 01:04 UTC, Amitay Isaacs 		martins: review+
Details
Patches for v4-7 (3.38 KB, patch)
2017-09-13 01:04 UTC, Amitay Isaacs 		martins: review+
Details
View All Add an attachment (proposed patch, testcase, etc.)

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Description Amitay Isaacs 2017-09-08 01:04:03 UTC 
CTDB recovers persistent databases using the database from the node with the highest sequence number.  Recovery helper sends GET_DB_SEQNUM control during recovery to read the sequence number.  At that time the databases are frozen and CTDB daemon has started a tdb transaction on the database.  CTDB daemon can only read a record from tdb using tdb_fetch() only if the tdb transaction has started.  Otherwise, CTDB daemon will block in tdb_fetch() to get a lock on the record causing deadlock.

This problem can be re-created also by stopping a node and trying to get the sequence number for any database.
Comment 1 Amitay Isaacs 2017-09-13 01:04:03 UTC 
Created attachment 13587 [details]
Patches for v4-6
Comment 2 Amitay Isaacs 2017-09-13 01:04:24 UTC 
Created attachment 13588 [details]
Patches for v4-7
Comment 3 Martin Schwenke 2017-09-13 01:22:24 UTC 
Hi Karolin,

This is ready for 4.6 and 4.7.

Thanks...
Comment 4 Karolin Seeger 2017-09-13 12:57:20 UTC 
(In reply to Martin Schwenke from comment #3)
Pushed to autobuild-v4-{7,6}-test.
Comment 5 Karolin Seeger 2017-09-14 14:12:34 UTC 
Pushed to both branches.
Closing out bug report.

Thanks!