from whoever has dequeued the item from the queue. Generally they have
no interest in the result, and even if it is called by the queuer, it
should still pretend that it was queued. The queuer should be assuming
that the call was queued and giving them the false confidence that they
are getting status leads to hard to find bugs.
Make it a void and remove all the code that tried to return status through it.
- Introduce ng_topo_mtx, a mutex to protect topology changes.
- In ng_destroy_node() protect with ng_topo_mtx the process
of checking and pointing at ng_deadnode. [1]
- In ng_con_part2() check that our peer is not a ng_deadnode,
and protect the check with ng_topo_mtx.
- Add KASSERTs to ng_acquire_read/write, to make more
understandible synopsis in case if called on ng_deadnode.
Reported by: Roselyn Lee [1]
- Introduce a new flags NGQF_QREADER and NGQF_QWRITER,
which tell how the item should be actually applied,
overriding NGQF_READER/NGQF_WRITER flags.
- Do not differ between pending reader or writer. Use only
one flag that is raised, when there are pending items.
- Schedule netgraph ISR in ng_queue_rw(), so that callers
do not need to do this job.
- Fix several comments.
Submitted by: julian
semantics, and then was reused for next node, it still would be applied
as writer again.
To fix the regression the decision is made never to alter item->el_flags
after the item has been allocated. This requires checking for overrides
both in ng_dequeue() and in ng_snd_item().
Details:
- Caller of the ng_apply_item() knows what is the current access to
node and specifies it to ng_apply_item(). The latter drops the
given access after item has beem applied.
- ng_dequeue() needs to be supplied with int pointer, where it stores
the obtained access on node.
- Check for node/hook access overrides in ng_dequeue().
times consequently, without checking whether callout has been serviced
or not. (ng_pptpgre and ng_ppp were catched in this behavior).
- In ng_callout() save old item before calling callout_reset(). If the
latter has returned 1, then free this item.
- In ng_uncallout() clear c->c_arg.
Problem reported by: Alexandre Kardanev
either reader or writer flag on item in the function, that
allocates the item. Do not modify these flags when item is
applied or queued.
The only exceptions are node and hook overrides - they can
change item flags to writer.
At the end of ng_snd_item(), node queue is processed. In certain
netgraph setups deep recursive calls can occur.
For example this happens, when two nodes are connected and can send
items to each other in both directions. If, for some reason, both nodes
have a lot of items in their queues, then the processing thread will
recurse between these two nodes, delivering items left and right, going
deeper in the stack. Other setups can suffer from deep recursion, too.
The following factors can influence risk of deep netgraph call:
- periodical write-access events on node
- combination of slow link and fast one in one graph
- net.inet.ip.fastforwarding
Changes made:
- In ng_acquire_{read,write}() do not dequeue another item. Instead,
call ng_setisr() for this node.
- At the end of ng_snd_item(), do not process queue. Call ng_setisr(),
if there are any dequeueable items on node queue.
- In ng_setisr() narrow worklist mutex holding.
- In ng_setisr() assert queue mutex.
Theoretically, the first two changes should negatively affect performance.
To check this, some profiling was made:
1) In general real tasks, no noticable performance difference was found.
2) The following test was made: two multithreaded nodes and one
single-threaded were connected into a ring. A large queues of packets
were sent around this ring. Time to pass the ring N times was measured.
This is a very vacuous test: no items/mbufs are allocated, no upcalls or
downcalls outside of netgraph. It doesn't represent a real load, it is
a stress test for ng_acquire_{read,write}() and item queueing functions.
Surprisingly, the performance impact was positive! New code is 13% faster
on UP and 17% faster on SMP, in this particular test.
The problem was originally found, described, analyzed and original patch
was written by Roselyn Lee from Vernier Networks. Thanks!
Submitted by: Roselyn Lee <rosel verniernetworks com>
an item may be queued and processed later. While this is OK for mbufs,
this is a problem for control messages.
In the framework:
- Add optional callback function pointer to an item. When item gets
applied the callback is executed from ng_apply_item().
- Add new flag NG_PROGRESS. If this flag is supplied, then return
EINPROGRESS instead of 0 in case if item failed to deliver
synchronously and was queued.
- Honor NG_PROGRESS in ng_snd_item().
In ng_socket:
- When userland sends control message add callback to the item.
- If ng_snd_item() returns EINPROGRESS, then sleep.
This change fixes possible races in ngctl(8) scripts.
Reviewed by: julian
Approved by: re (scottl)
specified by caller.
- Change ng_send_item() interface - use 'flags' argument instead of
boolean 'queue'.
- Extend ng_send_fn(), ng_package_data() and ng_package_msg()
interface - add possibility to pass flags. Rename ng_send_fn() to
ng_send_fn1(). Create macro for ng_send_fn().
- Update all macros, that use ng_package_data() and ng_package_msg().
Reviewed by: julian
SI_SUB_INIT_IF but before SI_SUB_DRIVERS. Make Netgraph(4)
framework initialize at SI_SUB_NETGRAPH level.
This does not address the bigger problem: MODULE_DEPEND
does not seem to work when modules are compiled in the
kernel, but it fixes the problem with Netgraph Bluetooth
device drivers reported by a few folks.
PR: i386/69876
Reviewed by: julian, rik, scottl
MFC after: 3 days
out c->c_func, we can't take it after callout_stop(). To take it before
we need to acquire callout_lock, to avoid race. This commit narrows
down area where lock is held, but hack is still present.
This should be redesigned.
Approved by: julian (mentor)
using linker_load_module(). This works OK if NGM_MKPEER message came
from userland and we have process associated with thread. But when
NGM_MKPEER was queued because target node was busy, linker_load_module()
is called from netisr thread leading to panic.
To workaround that we do not load modules by framework, instead ng_socket
loads module (if this is required) before sending NGM_MKPEER.
However, the race condition between return from NgSendMsg() and actual
creation of node still exist and needs to be solved.
PR: kern/62789
Approved by: julian
Also introduce a macro to be called by persistent nodes to signal their
persistence during shutdown to hide this mechanism from the node author.
Make node flags have a consistent style in naming.
Document the change.
is obviously not run a lot. (but is in some test cases).
This code is not usually run because it covers a case that doesn't
happen a lot (removing a node that has data traversing it).
for unknown events.
A number of modules return EINVAL in this instance, and I have left
those alone for now and instead taught MOD_QUIESCE to accept this
as "didn't do anything".
