Abstract: Concurrent resizing and modification of a first RCU-protected hash table includes allocating a second RCU-protected hash table, populating it by linking each hash bucket of the second hash table to all hash buckets of the first hash table containing elements that hash to the second hash table bucket, and publishing the second hash table. If the modifying comprises insertion, a new element is inserted at the head of a corresponding bucket in the second hash table. If the modifying comprises deletion, then within an RCU read-side critical section: (1) all pointers in hash buckets of the first and second hash tables that reference the element being deleted are removed or redirected, and (2) the element is freed following a grace period that protects reader references to the deleted element. The first table is freed from memory after awaiting a grace period that protects reader references to the first hash table.

Abstract: A technique for resizing a first RCU-protected hash table stored in a memory. A second RCU-protected hash table is allocated in the memory as a resized version of the first hash table having a different number of hash buckets, with the hash buckets being defined but initially having no hash table elements. The second hash table is populated by linking each hash bucket thereof to all hash buckets of the first hash table containing elements that hash to the second hash bucket. The second hash table is then published so that it is available for searching by hash table readers. The first table is freed from memory after waiting for a grace period which guarantees that no readers searching the first hash table will be affected by the freeing.

Abstract: A technique for resizing a first RCU-protected hash table stored in a memory. A second RCU-protected hash table is allocated in the memory as a resized version of the first hash table having a different number of hash buckets, with the hash buckets being defined but initially having no hash table elements. The second hash table is populated by linking each hash bucket thereof to all hash buckets of the first hash table containing elements that hash to the second hash bucket. The second hash table is then published so that it is available for searching by hash table readers. The first table is freed from memory after waiting for a grace period which guarantees that no readers searching the first hash table will be affected by the freeing.

Abstract: A technique for expediting the unloading of an operating system kernel module that executes read-copy update (RCU) callback processing code in a computing system having one or more processors. According to embodiments of the disclosed technique, an RCU callback is enqueued so that it can be processed by the kernel module's callback processing code following completion of a grace period in which each of the one or more processors has passed through a quiescent state. An expediting operation is performed to expedite processing of the RCU callback. The RCU callback is then processed and the kernel module is unloaded.

Abstract: Concurrent resizing and modification of a first RCU-protected hash table includes allocating a second RCU-protected hash table, populating it by linking each hash bucket of the second hash table to all hash buckets of the first hash table containing elements that hash to the second hash table bucket, and publishing the second hash table. If the modifying comprises insertion, a new element is inserted at the head of a corresponding bucket in the second hash table. If the modifying comprises deletion, then within an RCU read-side critical section: (1) all pointers in hash buckets of the first and second hash tables that reference the element being deleted are removed or redirected, and (2) the element is freed following a grace period that protects reader references to the deleted element. The first table is freed from memory after awaiting a grace period that protects reader references to the first hash table.

Abstract: A technique for expediting the unloading of an operating system kernel module that executes read-copy update (RCU) callback processing code in a computing system having one or more processors. According to embodiments of the disclosed technique, an RCU callback is enqueued so that it can be processed by the kernel module's callback processing code following completion of a grace period in which each of the one or more processors has passed through a quiescent state. An expediting operation is performed to expedite processing of the RCU callback. The RCU callback is then processed and the kernel module is unloaded.

Abstract: Data writers desiring to update data without unduly impacting concurrent readers perform a synchronization operation with respect to plural processors or execution threads. The synchronization operation is parallelized using a hierarchical tree having a root node, one or more levels of internal nodes and as many leaf nodes as there are processors or threads. The tree is traversed from the root node to a lowest level of the internal nodes and the following node processing is performed for each node: (1) check the node's children, (2) if the children are leaf nodes, perform the synchronization operation relative to each leaf node's associated processor or thread, and (3) if the children are internal nodes, fan out and repeat the node processing with each internal node representing a new root node. The foregoing node processing is continued until all processors or threads associated with the leaf nodes have performed the synchronization operation.

Abstract: A technique for making a free-running grace period counter safe against lengthy low power state processor sojourns. The grace period counter tracks grace periods that determine when processors that are capable executing read operations have passed through a quiescent state that guarantees the readers will no longer maintain references to shared data. Periodically, one or more processors may be placed in a low power state in which the processors discontinue performing grace period detection operations. Such processors may remain in the low power state for a complete cycle of the grace period counter. This scenario can potentially disrupt grace period detection operations if the processors awaken to see the same grace period counter value. To rectify this situation, processors in a low power state may be periodically awakened at a predetermined point selected prevent the low power state from extending for an entire roll over of the grace period counter.

Abstract: A technique for determining if a processor in a multiprocessor system implementing a read-copy update (RCU) subsystem may be placed in low power state. The technique may include determining whether the processor has any RCU callbacks that are ready for invocation or the RCU subsystem requires grace period advancement processing from the processor. The processor may be placed in a low power state if either (1) a first condition holds wherein the processor has one or more pending RCU callbacks, but does not have any RCU callbacks that are ready for invocation and the RCU subsystem does not require grace period advancement processing from the processor, (2) a second condition holds wherein the processor does not have any pending RCU callbacks.

Abstract: Dimensions of each physical object to be moved from an original physical site to a destination physical site are at least approximately determined. Each physical object is tagged with an identifier. A virtual layout of the destination physical site and the dimensions and the identifier of each physical object are input into a computer program. A user-specified location of where within the destination physical site each physical object is to be placed when moved to the destination physical site is input using the computer program, based on the virtual layout of the destination physical site and the dimensions and the identifier of each physical object. At the destination physical site, each physical object is looked up using the identifier of the physical object to determine the user-specified location of where to place the physical object within the destination physical site.

Abstract: A technique for implementing user-level read-copy update (RCU) with support for asynchronous grace periods. In an example embodiment, a user-level RCU subsystem is established that executes within threads of a user-level multithreaded application. The multithreaded application may comprise one or more reader threads that read RCU-protected data elements in a shared memory. The multithreaded application may further comprise one or more updater threads that perform updates to the RCU-protected data elements in the shared memory and register callbacks to be executed following a grace period in order to free stale data resulting from the updates. The RCU subsystem may implement two or more helper threads (helpers) that are created or selected as needed to track grace periods and execute the callbacks on behalf of the updaters instead of the updaters performing such work themselves.

Abstract: A technique for implementing user-level read-copy update (RCU) with support for asynchronous grace periods. In an example embodiment, a user-level RCU subsystem is established that executes within threads of a user-level multithreaded application. The multithreaded application may comprise one or more reader threads that read RCU-protected data elements in a shared memory. The multithreaded application may further comprise one or more updater threads that perform updates to the RCU-protected data elements in the shared memory and register callbacks to be executed following a grace period in order to free stale data resulting from the updates. The RCU subsystem may implement two or more helper threads (helpers) that are created or selected as needed to track grace periods and execute the callbacks on behalf of the updaters instead of the updaters performing such work themselves.

Abstract: A technique for managing read-copy update readers that have been preempted while executing in a read-copy update read-side critical section. A single blocked-tasks list is used to track preempted reader tasks that are blocking an asynchronous grace period, preempted reader tasks that are blocking an expedited grace period, and preempted reader tasks that require priority boosting. In example embodiments, a first pointer may be used to segregate the blocked-tasks list into preempted reader tasks that are and are not blocking a current asynchronous grace period. A second pointer may be used to segregate the blocked-tasks list into preempted reader tasks that are and are not blocking an expedited grace period. A third pointer may be used to segregate the blocked-tasks list into preempted reader tasks that do and do not require priority boosting.

Abstract: A technique for implementing read-copy update in a shared-memory computing system having two or more processors operatively coupled to a shared memory and to associated incoherent caches that cache copies of data stored in the memory. According to example embodiments disclosed herein, cacheline information for data that has been rendered obsolete due to a data update being performed by one of the processors is recorded. The recorded cacheline information is communicated to one or more of the other processors. The one or more other processors use the communicated cacheline information to flush the obsolete data from all incoherent caches that may be caching such data.

Abstract: A technique for managing read-copy update readers that have been preempted while executing in a read-copy update read-side critical section. A single blocked-tasks list is used to track preempted reader tasks that are blocking an asynchronous grace period, preempted reader tasks that are blocking an expedited grace period, and preempted reader tasks that require priority boosting. In example embodiments, a first pointer may be used to segregate the blocked-tasks list into preempted reader tasks that are and are not blocking a current asynchronous grace period. A second pointer may be used to segregate the blocked-tasks list into preempted reader tasks that are and are not blocking an expedited grace period. A third pointer may be used to segregate the blocked-tasks list into preempted reader tasks that do and do not require priority boosting.

Abstract: A technique for reducing reader overhead when referencing a shared data element while facilitating realtime-safe detection of a grace period for deferring destruction of the shared data element. The grace period is determined by a condition in which all readers that are capable of referencing the shared data element have reached a quiescent state subsequent to a request for a quiescent state. Common case local quiescent state tracking may be performed using only local per-reader state information for all readers that have not blocked while in a read-side critical section in which the data element is referenced. Uncommon case non-local quiescent state tracking may be performed using non-local multi-reader state information for all readers that have blocked while in their read-side critical section. The common case local quiescent state tracking requires less processing overhead than the uncommon case non-local quiescent state tracking.

Abstract: Hybrid multi-threaded access to data structures is provided in which hazard pointers are used for reads and locks are used for updates. Where a reader is attempting to read a data structure, the reader maintains a hazard pointer to the data structure before reading it, without globally acquiring a lock on the data structure. Upon the reader being finished reading the data structure, it removes the hazard pointer from the data structure. Where an updater is attempting to update the data structure, the updater globally acquires a lock on the data structure before updating it. Upon the updater being finished updating the data structure, it releases the lock from the data structure. To delete the data structure, first it is determined whether any hazard pointers point to the data structure, and where no hazard pointers do, the data structure is deleted.

Abstract: A computing system is provided with real-time capabilities so that the system is capable of running applications such that one or more real-time criteria are satisfied. An interrupt architecture of the computing system is disabled. The interrupt architecture generates interrupts sent to a firmware of the computing system in response to events. A different architecture is substituted within the computing system for the interrupt architecture. The different architecture is responsive to the events without violating the real-time criteria. In response to the events occurring, the different architecture causes one or more corrective actions to be performed.

Abstract: A technique for reducing reader overhead when referencing a shared data element while facilitating realtime-safe detection of a grace period for deferring destruction of the shared data element. The grace period is determined by a condition in which all readers that are capable of referencing the shared data element have reached a quiescent state subsequent to a request for a quiescent state. Common case local quiescent state tracking may be performed using only local per-reader state information for all readers that have not blocked while in a read-side critical section in which the data element is referenced. Uncommon case non-local quiescent state tracking may be performed using non-local multi-reader state information for all readers that have blocked while in their read-side critical section. The common case local quiescent state tracking requires less processing overhead than the uncommon case non-local quiescent state tracking.

Abstract: A technique for reducing reader overhead when referencing a shared data element while facilitating realtime-safe detection of a grace period for deferring destruction of the shared data element. The grace period is determined by a condition in which all readers that are capable of referencing the shared data element have reached a quiescent state subsequent to a request for a quiescent state. Common case local quiescent state tracking may be performed using only local per-reader state information for all readers that have not blocked while in a read-side critical section in which the data element is referenced. Uncommon case non-local quiescent state tracking may be performed using non-local multi-reader state information for all readers that have blocked while in their read-side critical section. The common case local quiescent state tracking requires less processing overhead than the uncommon case non-local quiescent state tracking.