There was a code flow error that would remove the expired ADB entry from
the LRU list and then a check in the expire_entry() would cause
assertion error because it expect the ADB entry to be linked.
Additionally, the expire mechanism would loop for cases when we would
held only a read rwlock; in such case we need to upgrade the lock and
try again, not just try again.
as there is no further use of isc_task in BIND, this commit removes
it, along with isc_taskmgr, isc_event, and all other related types.
functions that accepted taskmgr as a parameter have been cleaned up.
as a result of this change, some functions can no longer fail, so
they've been changed to type void, and their callers have been
updated accordingly.
the tasks table has been removed from the statistics channel and
the stats version has been updated. dns_dyndbctx has been changed
to reference the loopmgr instead of taskmgr, and DNS_DYNDB_VERSION
has been udpated as well.
change functions using isc_taskmgr_beginexclusive() to use
isc_loopmgr_pause() instead.
also, removed an unnecessary use of exclusive mode in
named_server_tcptimeouts().
most functions that were implemented as task events because they needed
to be running in a task to use exclusive mode have now been changed
into loop callbacks instead. (the exception is catz, which is being
changed in a separate commit because it's a particularly complex change.)
callback events from dns_resolver_createfetch() are now posted
using isc_async_run.
other modules which called the resolver and maintained task/taskmgr
objects for this purpose have been cleaned up.
The callbacks from dns_abd_createfind() are now posted using
isc_async_run() instead of isc_task_send(). ADB event types
have been replaced with a new dns_adbstatus_t type which is
included as find->status.
(The ADB still uses a task for dns_resolver_createfetch().)
dns_request_create() and _createraw() now take a 'loop' parameter
and run the callback event on the specified loop.
as the task manager is no longer used, it has been removed from
the dns_requestmgr structure. the dns_resolver_taskmgr() function
is also no longer used and has been removed.
Some compilers have a built-in definition of the _FORTIFY_SOURCE macro
that differs from BIND's preferred setting. This causes errors like
the one quoted below. The solution is to undefine the macro before
defining it. A similar fix was recently committed to glibc.
<command line>: error: '_FORTIFY_SOURCE' macro redefined
#define _FORTIFY_SOURCE 2
^
<built-in>: note: previous definition is here
#define _FORTIFY_SOURCE 0
^
https://sourceware.org/git/glibc.git/commitdiff/35bcb08eaa953c9b
Free/detach tsigkey and sig0key when exiting and then call
dst_lib_destroy if we have previously called dst_lib_init. This will,
in theory, allow OPENSSL_cleanup to free all memory.
Replace the isc_mutex in the dns_adb unit with isc_rwlock for better
performance. Both ADB names and ADB entries hashtables and LRU are now
using isc_rwlock.
This changes the internal isc_rwlock implementation to:
Irina Calciu, Dave Dice, Yossi Lev, Victor Luchangco, Virendra
J. Marathe, and Nir Shavit. 2013. NUMA-aware reader-writer locks.
SIGPLAN Not. 48, 8 (August 2013), 157–166.
DOI:https://doi.org/10.1145/2517327.24425
(The full article available from:
http://mcg.cs.tau.ac.il/papers/ppopp2013-rwlocks.pdf)
The implementation is based on the The Writer-Preference Lock (C-RW-WP)
variant (see the 3.4 section of the paper for the rationale).
The implemented algorithm has been modified for simplicity and for usage
patterns in rbtdb.c.
The changes compared to the original algorithm:
* We haven't implemented the cohort locks because that would require a
knowledge of NUMA nodes, instead a simple atomic_bool is used as
synchronization point for writer lock.
* The per-thread reader counters are not being used - this would
require the internal thread id (isc_tid_v) to be always initialized,
even in the utilities; the change has a slight performance penalty,
so we might revisit this change in the future. However, this change
also saves a lot of memory, because cache-line aligned counters were
used, so on 32-core machine, the rwlock would be 4096+ bytes big.
* The readers use a writer_barrier that will raise after a while when
readers lock can't be acquired to prevent readers starvation.
* Separate ingress and egress readers counters queues to reduce both
inter and intra-thread contention.
The dns_badcache was pulling the <isc/atomic.h> header only indirectly
via <isc/rwlock.h>, add the direct include as the <isc/rwlock.h> no
longer pulls the header when pthread_rwlock is used.
Include MD5 feature detection in featuretest tool and use it in some
places. When RHEL distribution or Fedora ELN is in FIPS mode, then MD5
algorithm is unavailable completely and even hmac-md5 algorithm usage
will always fail. Work that around by checking MD5 works and if not,
skipping its usage.
Those changes were dragged as downstream patch bind-9.11-fips-tests.patch
in Fedora and RHEL.
