Re: (ITS#5814) concurrent access to connections

[ando@sys-net.it]

ando@sys-net.it wrote:
> Full_Name: Pierangelo Masarati
> Version: HEAD/re24
> OS: irrelevant
> URL: ftp://ftp.openldap.org/incoming/
> Submission from: (NULL) (81.72.89.40)
> Submitted by: ando
> 
> 
> There is code that accesses c_conn_state and c_struct_state while not adequately
> mutex-protected.  In most cases, this code basically consists in assertions, so
> we risk a core dump because of an assertion on non-mutex protected data.  This
> is the case (as happened to me) of connection_next().
> 
> I have a fix for the case I noticed, with two unhandled asserts (marked with a
> FIXME) because I'm not sure whether it's worth to add extra mutexes just to be
> able to safely assert, or remove assertions.
> 
> Committing the fix; there might be more.  Please check.

I noticed this while testing concurrency for re24; here is the relevant 
portion of the core dump:

(gdb) bt
#0  0x00483402 in __kernel_vsyscall ()
#1  0x00c9ad20 in raise () from /lib/libc.so.6
#2  0x00c9c631 in abort () from /lib/libc.so.6
#3  0x00c9416b in __assert_fail () from /lib/libc.so.6
#4  0x08084b80 in connection_next (c=0x0, index=0xb62e3d8c) at 
../../../ldap-2.4-src/servers/slapd/connection.c:871
#5  0x081a810c in monitor_subsys_conn_update (op=0x8a145f0, 
rs=0xb62e5128, e=0x896632c) at 
../../../../ldap-2.4-src/servers/slapd/back-monitor/conn.c:230

<snip>

(gdb) f 4
#4  0x08084b80 in connection_next (c=0x0, index=0xb62e3d8c) at 
../../../ldap-2.4-src/servers/slapd/connection.c:871
(gdb) p connections[*index]
$1 = {c_struct_state = 2, c_conn_state = 1, c_conn_idx = 19, c_sd = 19,
<snip>

Cheers, p.


Ing. Pierangelo Masarati
OpenLDAP Core Team

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