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lwq is a FIFO single-linked queue that only requires a spinlock for dequeueing, which happens in process context. Enqueueing is atomic with no spinlock and can happen in any context. This is particularly useful when work items are queued from BH or IRQ context, and when they are handled one at a time by dedicated threads. Avoiding any locking when enqueueing means there is no need to disable BH or interrupts, which is generally best avoided (particularly when there are any RT tasks on the machine). This solution is superior to using "list_head" links because we need half as many pointers in the data structures, and because list_head lists would need locking to add items to the queue. This solution is superior to a bespoke solution as all locking and container_of casting is integrated, so the interface is simple. Despite the similar name, this solution meets a distinctly different need to kfifo. kfifo provides a fixed sized circular buffer to which data can be added at one end and removed at the other, and does not provide any locking. lwq does not have any size limit and works with data structures (objects?) rather than data (bytes). A unit test for basic functionality, which runs at boot time, is included. Signed-off-by: NeilBrown <neilb@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com> Cc: Kees Cook <keescook@chromium.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: David Gow <davidgow@google.com> Cc: linux-kernel@vger.kernel.org Message-Id: <20230911111333.4d1a872330e924a00acb905b@linux-foundation.org> Signed-off-by: Chuck Lever <chuck.lever@oracle.com> |
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