> For the complete documentation index, see [llms.txt](https://lagnos.gitbook.io/linux-kernel-notes/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://lagnos.gitbook.io/linux-kernel-notes/core-apis/core-utilities/notification-mechanism.md).

# Notification Mechanism

* Built on top of the standard pipe driver
* can be enabled by `CONFIG_WATCH_QUEUE`
* [splicing](/linux-kernel-notes/implementations/pipes.md#splice) is disabled on these pipes to prevent inter-leaving of kernel messages
* owner of the pipe has to tell the kernel, the sources from which it would like to get notifications
* a message will be discarded if there isn’t a slot available in the ring or if no preallocated message buffer is available. In both of these cases
* the kernel **does not wait** for the consumers to collect it, but rather just continues on.
  * This means that **notifications can be generated whilst spinlocks are held** and also protects the kernel from being held up indefinitely by a userspace malfunction.

Please refer [General notification mechanism - Kernel Docs](https://docs.kernel.org/core-api/watch_queue.html) for information on Mesage Structure, Watch Queue, Watch List and Event Filtering.