I am searching for a counterpart function with attach_kprobe(), which can detach the probe we insert previously.
If it doesn't exist, are there any possible to detach inserted probe in same program using Python?
Any suggestion will be appreciated!
detach_kprobe() is what you are looking for:
b.attach_kprobe(event="nfs_file_read", fn_name="trace_entry")
b.attach_kprobe(event="nfs_file_read")
I'm not sure why the documentation for that function is missing, but I'm sure the bcc maintainers would welcome a pull request to add it.
Related
I found some example code online that I'm trying to use to do a CNAME record lookup (notice that I pass a callback block that I want to be run):
DNSServiceQueryRecord(serviceRef, 0, 0, domainName, UInt16(kDNSServiceType_CNAME), UInt16(kDNSServiceClass_IN), callback, &mutableCompletionHandler);
DNSServiceProcessResult(serviceRef.pointee)
The problem is that this code is getting blocked at DNSServiceProcessResult(serviceRef.pointee) and the callback is never called. According to Apple's documentation for DNSServiceProcessResult, I need to
Use DNSServiceRefSockFD in conjunction with a run loop or select() to determine the presence of a response from the server before calling this function to process the reply without blocking.
So I looked at DNSServiceRefSockFD and found that I could create a dnssd_sock_t with DNSServiceRefSockFD(serviceRef.pointee). But now that I have the socket, I'm not sure how to "use it in conjunction with a run loop" as an event source for the run loop (according to the DNSServiceRefSockFD documentation).
I'm just not understanding how this works. I don't understand how to use the dnsssd_sock_t as an event source to a run loop so that I can call DNSServiceProcessResult at the right time without blocking so that my callback will actually run.
If it's better to use the socket as a kqueue event source or in a select() loop (as the documentation mentions), I'm fine with that, but I don't know how to do that either.
CoreFoundation can be quite cryptic, so any help is much appreciated!
And if there's a better way to do a CNAME record lookup then, by all means, please share!
See my (ethan-gerardot) comments on https://gist.github.com/fikeminkel/a9c4bc4d0348527e8df3690e242038d3
The first paragraph answers how to get the callback to be called without blocking.
I have a general question about how to debug in Simpy. Normal debugging tools don't seem to work, since everything is working on the event loop, and you can't step through the code line by line and inspect what exists at any point in time.
Primarily, I'm interested in finding what kinds of processes and callbacks are in existence at a particular time, and how to remove them at the appropriate point. Are there any best practices surrounding debugging in discrete event simulation generally?
I would just use a bunch of print()s.
One thing you might find useful is the specific requests that can be passed to primitives such as resources. For example you can ask a resource how many users it currently has or how big the queue to use the resource is with:
All of these commands can be found in the documentation, here is the resource example: https://simpy.readthedocs.io/en/latest/api_reference/simpy.resources.html
I´ve read that it´s possible to share sockets between processes. Is this also possible in Node.js?
I saw the cluster api in node.js, but that´s not what I´m looking for. I want to be able to accept a connection in one process, maybe send & read a bit, and after a while pass this socket to another fully independent node.js process.
I could already do this with piping, but I don´t want to do this, since it´s not as fast as directly reading/writing to the socket itself.
Any ideas?
Update
I found the following entry in the node.js documentation:
new net.Socket([options]) #
Construct a new socket object.
options is an object with the following defaults:
{ fd: null
type: null
allowHalfOpen: false
}
fd allows you to specify the existing file descriptor of socket. type specified underlying protocol. It can be 'tcp4', 'tcp6', or 'unix'. About allowHalfOpen, refer to createServer() and 'end' event.
I think it would be possible to set the "fd" property to the filedescriptor of the socket and then open the socket with that. But... How can I get the filedescriptor of the socket and pass it to the process that needs it?
Thanks for any help!
This is not possible at the moment, but I've added it as a feature request to the node issues page.
Update
In the mean time, I've written a module for this. You can find it here: https://github.com/VanCoding/node-ancillary
You probably want to take a look at hook.io
hook.io is a distributed EventEmitter built on node.js. In addition to providing a minimalistic event framework, hook.io also provides a rich network of hook libraries for managing all sorts of input and output.
I have a cluster of 10 memcaches, using consistent hashing. When the key passed to memcached_get() is searched on the unavailable server I get just MEMCACHED_SERVER_MARKED_DEAD response (return value).
I would expect the key should be redistributed to the next available server in this case and I should get NOTFOUND from the next memcached_get() call. However I'm still getting MEMCACHED_SERVER_MARKED_DEAD and so I'm unable to set a new value.
I discovered I can call memcached_behavior_set(..., MEMCACHED_BEHAVIOR_DISTRIBUTION). This causes hash redistribution and it works as I wish then. However, I do not think it is a good approach. Is it?
Generally you want to enable MEMCACHED_BEHAVIOR_DISTRIBUTION from the start if you are dealing with multiple memcached pools. So yes that solution will work.
If you are having further problems, take a look at MEMCACHED_BEHAVIOR_REMOVE_FAILED_SERVERS that will auto purge failed servers from pool after x number of failures.
I found the answer myself.
https://bugs.launchpad.net/libmemcached/+bug/777672
Applying the patch solved all my problems. Note, I wonder it has beed broken since 0.39 and nobody has cared.
Trying this free forum for developers. I am migrating a serial driver to kernel 2.6.31.5. I have used various books and articles to solve problems going from 2.4
Now I have a couple of kill_proc that is not supported anymore in kernel 2.6.31.5
What would be the fastest way to migrate this into the kernel 2.6.31.5 way of killing a thread. In the books they say use kill() but it does not seem to be so in 2.6.31.5. Using send_signal would be a good way, but how do I do this? There must be a task_struct or something, I wich I could just provide my PID and SIGTERM and go ahaed and kill my thread, but it seems more complicated, having to set a struct with parameters I do not know of.
If anyone have a real example, or a link to a place with up to date info on kernel 2.6.31 I would be very thankful. Siply put, I need to kill my thread, and this is not suppose to be hard. ;)
This is my code now:
kill_proc(ex_pid, SIGTERM, 1);
/Jörgen
For use with kthreads, there is now kthread_stop that the caller (e.g. the module's exit function) can invoke. The kthread itself has to check using kthread_should_stop. Examples of that are readily available in the kernel source tree.