https://bugs.openldap.org/show_bug.cgi?id=9278
Issue ID: 9278
Summary: liblmdb: robust mutexes should not be unmapped
Product: LMDB
Version: unspecified
Hardware: All
OS: FreeBSD
Status: UNCONFIRMED
Severity: normal
Priority: ---
Component: liblmdb
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Created attachment 736
--> https://bugs.openldap.org/attachment.cgi?id=736&action=edit
A possible workaround
We recently noticed that lmdb would have the memory region containing the
robust mutex unmapped on mdb_env_close0():
munmap((void *)env->me_txns,
(env->me_maxreaders-1)*sizeof(MDB_reader)+sizeof(MDB_txninfo));
Note that if this is the last unmap for a robust mutex, the FreeBSD
implementation would garbage-collect the mutex, making it no longer visible to
other processes. As the result, a second instance of the attached test.c (from
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=244493 with minor changes)
would trigger the assertion at mdb_txn_begin() because the acquisition of the
mutex would return 22 (EINVAL), because the mutex appeared to be a robust
mutex, but was invalid.
The attached lmdb.diff is a possible workaround for this (it would skip
unmapping when setting up the robust mutex for the first time).
--
You are receiving this mail because:
You are on the CC list for the issue.
