A new function vlog_insert_module() is introduced to avoid using
list_insert() from the vlog.h header.
Signed-off-by: Thomas Graf <tgraf@noironetworks.com>
Acked-by: Ben Pfaff <blp@nicira.com>
struct list is a common name and can't be used in public headers.
Signed-off-by: Thomas Graf <tgraf@noironetworks.com>
Acked-by: Ben Pfaff <blp@nicira.com>
On current master, the per-thread callback event set is flushed
when ovsrcu_quiesce_start() is called or when the callback
event set is full. For threads that only call 'ovsrcu_quiesce()'
to indicate quiescient state, their callback event set will not
be flushed for execution until the set is full. And this could
take a very long time.
Theoretically, this should not be an issue, since rcu postponed
callback events should only free the old version of objects.
However, current ovs does not follow this rule, and some callback
events include other activities like unregistering the netdev
from global name-netdev map. The delay of unregistering the netdev
(by threads that only calls ovsrcu_quiesce()) will prevent the
recreate of same netdev indefinitely.
As a short-term workaround, this commit makes every call to
ovsrcu_quiesce() flush the callback event set. In the long run,
there will be a refactor of the use of ovs-rcu module, in which all
callback events only free the old version of objects.
Signed-off-by: Alex Wang <alexw@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
When a reference counted object is also RCU protected the deletion of
the object's memory is always postponed. This allows
memory_order_relaxed to be used also for unreferencing, as RCU
quiescing provides a full memory barrier (it has to, or otherwise
there could be lingering accesses to objects after they are recycled).
Also, when access to the reference counted object is protected via a
mutex or a lock, the locking primitives provide the required memory
barrier functionality.
Also, add ovs_refcount_try_ref_rcu(), which takes a reference only if
the refcount is non-zero and returns true if a reference was taken,
false otherwise. This can be used in combined RCU/refcount scenarios
where we have an RCU protected reference to an refcounted object, but
which may be unref'ed at any time. If ovs_refcount_try_ref_rcu()
fails, the object may still be safely used until the current thread
quiesces.
Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
lib/ovs-rcu.h had some of the comments duplicated.
Add ovsrcu_init() that can be used like ovsrcu_set() when the RCU
protected pointer is not yet visible any readers.
ovs-rcu internal initialization function is renamed as ovsrcu_init_module().
Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
The main thread has the empty string as its name, but that's not a good
log string.
Without this patch we can get log message like
blocked 1000 ms waiting for to quiesce
from ovsrcu_synchronize().
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Alex Wang <alexw@nicira.com>
Thread names are occasionally very useful for debugging, but from time to
time we've forgotten to set one. This commit adds the new thread's name
as a parameter to the function to start a thread, to make that mistake
impossible. This also simplifies code, since two function calls become
only one.
This makes a few other changes to the thread creation function:
* Since it is no longer a direct wrapper around a pthread function,
rename it to avoid giving that impression.
* Remove 'pthread_attr_t *' param that every caller supplied as NULL.
* Change 'pthread *' parameter into a return value, for convenience.
The system-stats code hadn't set a thread name, so this fixes that issue.
This patch is a prerequisite for making RCU report the name of a thread
that is blocking RCU synchronization, because the easiest way to do that is
for ovsrcu_quiesce_end() to record the current thread's name.
ovsrcu_quiesce_end() is called before the thread function is called, so it
won't get a name set within the thread function itself. Setting the thread
name earlier, as in this patch, avoids the problem.
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Alex Wang <alexw@nicira.com>
Otherwise ovsrcu_synchronize() busy-waits in its loop because its
poll_block() un-quiesces, causing the global_seqno to increase, which is
what it waits for.
Reported-by: Alex Wang <alexw@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Alex Wang <alexw@nicira.com>
The ovs-rcu module adds a new thread for checking the grace period.
Since the thread name is not set, it will inherit the name of the
thread that creates it. This makes the 'top' output quite confusing.
This commit names the thread to 'urcu' for clarity.
Acked-by: Ben Pfaff <blp@nicira.com>
Signed-off-by: Alex Wang <alexw@nicira.com>
This commit fixes a bug introduced by 0f2ea848(ovs-rcu: New library.).
It is possible that ovsrcu_quiesce() is called before ovsrcu_init().
So, it is necessary to call ovsrcu_init() in ovsrcu_quiesce().
Signed-off-by: Alex Wang <alexw@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
RCU allows multiple threads to read objects in parallel without any
performance penalty. The following commit will introduce the first use.
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Andy Zhou <azhou@nicira.com>
