What is Signalfd?

What is Signalfd?

signalfd() creates a file descriptor that can be used to accept signals targeted at the caller. This provides an alternative to the use of a signal handler or sigwaitinfo(2), and has the advantage that the file descriptor may be monitored by select(2), poll(2), and epoll(7).

What is Eventfd?

eventfd() creates an “eventfd object” that can be used as an event wait/notify mechanism by user-space applications, and by the kernel to notify user-space applications of events. The object contains an unsigned 64-bit integer (uint64_t) counter that is maintained by the kernel.

What is Epoll_wait?

The epoll_wait() system call waits for events on the epoll(7) instance referred to by the file descriptor epfd. Specifying a timeout of -1 causes epoll_wait() to block indefinitely, while specifying a timeout equal to zero cause epoll_wait() to return immediately, even if no events are available.

Is Eventfd thread safe?

1 Answer. Writing to an eventfd is thread safe, i.e., two threads (or even processes) are allowed to write to the same fd at the same time, and they will be properly serialized.

What is Epoll_ctl?

DESCRIPTION top. This system call is used to add, modify, or remove entries in the interest list of the epoll(7) instance referred to by the file descriptor epfd. It requests that the operation op be performed for the target file descriptor, fd.

What is Nginx epoll?

When one request needs to make a network request (say, to a backend), Nginx attaches a callback to the backend request and then works on another active client request. In practice, this means it returns to the event loop ( epoll , kqueue , or select ) and asks for file descriptors that have something to report.

What is epoll Kqueue?

Kqueue is a scalable event notification interface introduced in FreeBSD 4.1 on July 2000, also supported in NetBSD, OpenBSD, DragonFly BSD, and macOS. Kqueue makes it possible for software like nginx to solve the c10k problem. Kqueue provides efficient input and output event pipelines between the kernel and userland.

What is zombie state?

Zombie state: When a process is created in UNIX using fork() system call, the address space of the Parent process is replicated. If the parent process calls wait() system call, then the execution of the parent is suspended until the child is terminated.

What is O_nonblock?

O_NONBLOCK is a property of the open file description, not of the file descriptor, nor of the underlying file. Yes, you could have separate file descriptors open for the same file, one of which is blocking and the other of which is non-blocking.

What is Epollexclusive?

EPOLLEXCLUSIVE (since Linux 4.5) Sets an exclusive wakeup mode for the epoll file descriptor that is being attached to the target file descriptor, fd. The default in this scenario (when EPOLLEXCLUSIVE is not set) is for all epoll file descriptors to receive an event.

What is the difference between glibc_ and glibcxx_symbol versions?

GLIBC_and GLIBCXX_symbol versions have no intrinsic relationship. GLIBC_belongs to glibc, and GLIBCXX_to libstdc++. libstdc++ can be built against many different glibc versions, and this can result in different GLIBC_version references, but the set of GLIBCXX_versions is not changed by that.

Is glibcxx library dependent from OS?

17 I solved problem like this (but GLIBCXX_3.4.21 on CentOS) but it is not dependent from os. The library is part of gcccompiler so need to install or compile appropriate version of gcc. This is table of versions of gccand versions of appropriate libstdc++:

Why does the glibc signalfd() wrapper function not include a flag argument?

The glibc signalfd () wrapper function does not include this argument, since it provides the required value for the underlying system call. There are two underlying Linux system calls: signalfd () and the more recent signalfd4 (). The former system call does not implement a flags argument.

What is signalfd and how does it work?

So, in 2007, Linux gained an API called signalfd, which lets you create a file descriptor that notifies on signals. The idea is that you can avoid the complexity of the self-pipe trick, as well as any problems with EINTR, by just asking the kernel to send you signals via a file descriptor in the first place.

https://www.youtube.com/watch?v=dYLxCPVFZ4s