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If dbwrap_watched_watch_recv() returns IO_TIMEOUT, "blockerdead" might
be an uninitialized non-false, and further down we'll remove the wrong
exclusive locker.
Bug: https://bugzilla.samba.org/show_bug.cgi?id=14636
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Fri Mar 5 11:22:07 UTC 2021 on sn-devel-184
We don't require a sequence number that is incremented,
we just need a value that's not reused.
We use the new generate_unique_u64(), which is much cheaper!
Using smbtorture3 //foo/bar -U% local-g-lock-ping-pong -o 500000
under valgrind --tool=callgrind...
This change replaces this:
13,129,925,659 PROGRAM TOTALS
4,125,752,958 ???:_nettle_sha256_compress [/usr/lib/x86_64-linux-gnu/libnettle.so.6.4]
1,257,005,866 ???:_nettle_aes_encrypt [/usr/lib/x86_64-linux-gnu/libnettle.so.6.4]
590,000,773 bin/default/../../lib/tdb/common/lock.c:tdb_lock_list
571,503,429 ???:_nettle_aes_set_key [/usr/lib/x86_64-linux-gnu/libnettle.so.6.4]
479,000,608 bin/default/../../lib/tdb/common/lock.c:tdb_unlock
...
by this:
6,877,826,377 PROGRAM TOTALS
590,000,773 bin/default/../../lib/tdb/common/lock.c:tdb_lock_list
479,000,608 bin/default/../../lib/tdb/common/lock.c:tdb_unlock
...
12,500,033 bin/default/../../lib/util/genrand_util.c:generate_unique_u64
...
8,996,970 ???:_nettle_sha256_compress [/usr/lib/x86_64-linux-gnu/libnettle.so.6.4]
time smbtorture3 //foo/bar -U% local-g-lock-ping-pong -o 5000000
gives:
537426 locks/sec
real 0m19,071s
user 0m15,061s
sys 0m3,999s
vs.
900956 locks/sec
real 0m11,155s
user 0m8,293s
sys 0m2,860s
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Optionally allow a database with g_lock format to participate in the dbwarp
lock order check. Will be used once locking.tdb is based upon g_lock.c
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Same concept as dbwrap_watched_watch_send/recv: Get informed if the
underlying data of a record changes. This utilizes the watched
database that g_lock is based upon anyway. To avoid spurious wakeups
by pure g_lock operations this patch adds a sequence number for the
data that is stored in the g_lock data field.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
When contending a WRITE with an existing READ, the contender puts
himself into the exclusive slot, waiting for the READers to go
away. If the async lock request is canceled before we got the lock, we
need to remove ourselves again. This is done in the destructor of the
g_lock_lock_state. In the successful case, the destructor needs to go
away.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Sun Dec 22 18:57:17 UTC 2019 on sn-devel-184
The comment "this is used in very hot code paths" is not true right now, but
will get true soon....
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Now we have one fixed field for the exclusive lock holder and an array
of shared locks. This way we now prioritize writers over readers: If a
pending write comes in while readers are active, it will put itself
into the exclusive slot. Then it waits for the readers to vanish. Only
when all readers are gone the exclusive lock request is granted. New
readers will just look at the exclusive slot and see it's taken. They
will then line up as watchers, retrying whenever things change.
This also means that it will be cheaper to support many shared locks:
Granting a shared lock just means to extend the array. We don't have
to walk the array for possible conflicts.
This also adds explicit UPGRADE and DOWNGRADE operations for better
error checking.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
This will allow using the g_lock.c logic on other databases as well
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Soon the g_lock database format will change. There will be one
exclusive entry and an array of shared entries. In that format,
there's no need to attach a lock_type to each entry in the g_lock
database. Reflect this change in the g_lock_dump API
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Avoid a call to dbwrap_record_get_value(), dbwrap_do_locked() already
gave us the value.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
I want to reduce dbwrap_record_get_value(). It makes the caller believe it can
make a copy of the TDB_DATA returned and that the value remains constant. It's
not, as you can always do a dbwrap_record_store().
This patch removes one requirement for getting the value out of a
db_record via dbwrap_record_get_value(). You can still make a copy, but from an
API perspective to me it's more obvious that "value" as a parameter to the
callback has a limited lifetime.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
This puts too much logic into this lowlevel infrastructure module,
given the two minor external users.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Wed May 8 17:47:39 UTC 2019 on sn-devel-184
Point out in the API that "backend" talloc_moves into the watched
database.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Fri Aug 17 21:29:15 CEST 2018 on sn-devel-144
Fix a confusing API: Many places TALLOC_FREE the path where it's not
clear you have to do it.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
While chasing a bug in g_lock (not in master) I saw some opportunity to
simplify g_lock_trylock a bit. This is array handling, and array
handling is just extremely error-prone. This *might* be a little less
efficient or large numbers of READ locks, but this remains to be
seen. For now, simplify the code.
First, we make two passes now: One to remove ourselves, and the other
one to search for conflicts. Mixing up both made it pretty hard for me
to follow the code.
Second, I've removed the _mylock and mylock pointer/struct logic and
replaced it with the "mylock.pid.pid != 0 ? &mylock : NULL" when calling
g_lock_store. To me, this focuses the logic whether to add ourselves in
one place instead of spreading it around in the whole routine.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Tue Aug 14 11:42:10 CEST 2018 on sn-devel-144
If we try to G_LOCK_READ while a G_LOCK_WRITE is active, we do the
serverid_exists call twice. Avoid that.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
tevent_req_set_endtime internally already calls tevent_req_nomem and thus sets
the error status correctly.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Thu Feb 8 14:50:49 CET 2018 on sn-devel-144
g_lock_trylock() always incremented the counter 'i', even after cleaning a stale
entry at position 'i', which means it skipped checking for a conflict against
the new entry at position 'i'.
As result a process could get a write lock, while there're still
some read lock holders. Once we get into that problem, also more than
one write lock are possible.
BUG: https://bugzilla.samba.org/show_bug.cgi?id=13195
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Wed Dec 20 20:31:48 CET 2017 on sn-devel-144
Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Sun Dec 10 00:46:26 CET 2017 on sn-devel-144
The initial idea was to have some "atomicity" in this API. Every
caller interested in a record would have to do something with
it once it changes. However, only one caller really used this
feature, and that is easily changed to not use it. So
remove the complexity.
Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
