Abstract: A system, method and computer program product for atomically moving a shared list element from a first list location to a second list location includes inserting a placeholder element at the second list location to signify to readers that a move operation is underway, removing the shared list element from the first list location, re-identifying the list element to reflect its move from the first list location to the second list location, inserting it at the second list location and unlinking the placeholder element. A deferred removal of the placeholder element is performed following a period in which readers can no longer maintain references thereto. A method, system and computer program product are additionally provided for performing a lookup of a target list element that is subject to being atomically moved from a first list to a second list.

Abstract: A method and apparatus for restricting access of an application to computer hardware. The apparatus includes both an authentication module and a validation module. The authentication module is within the trusted firmware layer. The purpose of the authentication module is to verify a cryptographic key presented by an application. The validation module is responsive to the authentication module and limits access of the application to the computer hardware. The authentication modules may be implemented in software through a firmware call, or through a hardware register of the computer.

Abstract: A method and apparatus are provided for maintaining data integrity when switching between data protection methods. Data and a first protection type information are received. A second protection type information is generated. After generating the second protection type information, the data is checked using the first protection type information. An error indication is generated when the first protection type information check fails.

Abstract: A system and method is provided to support immediate freeing of a designated element from memory. Following a process of designating an element for removal from a data-structure, conditional limitations are used to determine if immediate freeing of the element from memory is available. The conditional limitations include determining that the instruction originates from a uniprocessor computer system. In addition, the conditional limitations include a determination as to whether a call_rcu primitive or synchronize_kernel primitive may be omitted, or whether the computer implemented instruction is operating in an interrupt handler. If the conditional limitations are met, the designated element may be immediately freed from memory.

Abstract: Read-copy-update (RCU) is performed within real-time and other types of systems, such that memory barrier usage within RCU is reduced. A computerized system includes processors, memory, updaters, and readers. The updaters update contents of a section of the memory by using first and second sets of per-processor counters, first and second sets of per-processor need-memory-barrier bits, and a global flip-counter bit. The global flip-counter bit specifies which of the first or second set of the per-processor counters and the per-processor need-memory-barrier bits is a current set, and which is a last set. The readers read the contents of the section of the memory by using the first and second sets of per-processor counters, the first and second sets of per-processor need-memory-barrier bits, and the global flip-counter bit, in a way that significantly reduces the need for memory barriers during such read operations.

Abstract: A method and apparatus for restricting access of an application to computer hardware. The apparatus includes both an authentication module and a validation module. The authentication module is within the trusted firmware layer. The purpose of the authentication module is to verify a cryptographic key presented by an application. The validation module is responsive to the authentication module and limits access of the application to the computer hardware. The authentication modules may be implemented in software through a firmware call, or through a hardware register of the computer.

Abstract: Atomic renaming and moving of data files, while permitting lock-free look-ups to the data files, is disclosed. A temporary record may be created within a hash chain encompassing a record for a data file and corresponding to a location of the data file within a computer file system. The temporary record is linked within the hash chain so that the temporary record points to the same records to which the record for the data file points. The record for the data file is renamed with a new name, and/or moved to a new location within the computer file system, and the temporary record is removed from the hash chain. Before the temporary record is removed, look-ups of the data file resolve to the temporary record, the temporary record causing the look-ups to wait until the record for the data file has been renamed and/or moved and the temporary record removed.

Abstract: Utilizing a hardware transactional approach to execute a code section by employing pseudo-transactions, after initially utilizing software locking, is disclosed. A method is disclosed that utilizes a software approach to locking memory to execute a code section relating to memory. The software approach employs a pseudo-transaction to determine whether a hardware approach to transactional memory to execute the threshold would have been successful. Where the hardware approach to transactional memory to execute the code section satisfies a threshold based on success of at least the pseudo-transaction, the method subsequently utilizes the hardware approach to execute the code section. The hardware approach may include starting a transaction inclusive of the code section, conditionally executing the transaction, and, upon successfully completing the transaction, committing execution of the transaction to the memory to which the code section relates.

Abstract: A technique for realtime-safe detection of a grace period for deferring the destruction of a shared data element until pre-existing references to the data element have been removed. A per-processor read/write lock is established for each of one or more processors. When reading a shared data element at a processor, the processor's read/write lock is acquired for reading, the shared data element is referenced, and the read/write lock that was acquired for reading is released. When starting a new grace period, all of the read/write locks are acquired for writing, a new grace period is started, and all of the read/write locks are released.

Abstract: A technique for realtime-safe detection of a grace period for deferring the destruction of a shared data element until pre-existing references to the data element have been removed. A pair of counters is established for each of one or more processors. A global counter selector determines which counter of each per-processor counter pair is a current counter. When reading a shared data element at a processor, the processor's current counter is incremented. Following counter incrementation, the processor's counter pair is tested for reversal to ensure that the incremented counter is still the current counter. If a counter reversal has occurred, such that the incremented counter is no longer current, the processor's other counter is incremented. Following referencing of the shared data element, any counter that remains incremented is decremented.

Abstract: Provided is a method, system, and program for scheduling operations called by a task on a real-time or non-real-time processor. Execution durations are provided for operations. A call is received from a task for an operation. A determination is made of a latency requirement for a first processor and of the execution duration of the called operation. The called operation is executed on the first processor in response to determining that the determined execution duration is less than the latency requirement. The called operation is executed on a second processor in response to determining that the determined execution duration is greater than the latency requirement.

Abstract: Typical embodiments of the present invention maintain the cache metadata in arrays, and use vector instructions to process the array elements in parallel. The cache metadata comprises virtual tags corresponding to main memory addresses and physical addresses corresponding to cache memory addresses. The virtual tags and physical addresses may be interleaved in a single array in the cache memory. Alternately, virtual tags and physical addresses may be maintained in corresponding separate arrays. A roving pointer may be used to identify the next block to be ejected from the cache memory.

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 flag and a wait period are used to guarantee that readers of two data values see the updated first value before they see the updated second value, where the second value has to be updated after the first value is updated and thus is dependent on the first value. The first value is updated, and a flag associated with the first data value is set. The flag effectively prevents further updating of the first data value until it has been cleared. A length of time is waited for, such that any reading of the first data value and the second data value is guaranteed to not see the second data value as updated unless the first data value is also seen as updated. The flag is then cleared, such that further updating of the first data value can again occur. The second data value is finally updated.

Abstract: A general purposed operating system is modified to support hard real-time processing of hard real-time tasks. At least one processing unit in the operating system is designated as a hard real-time processing unit to process hard real-time tasks, and at least one processing unit in the operating system is designated as a non-hard real-time processing unit to process non-hard real-time tasks and designated non-deterministic processing steps. Hard real-time tasks assigned to the non-hard real-time processing unit may be transferred to the hard real-time processing unit, and tasks assigned to the hard real-time processing unit that are about to execute a non-deterministic processing step may be transferred to the non-hard real-time processing unit.

Abstract: A method, apparatus and program storage device for performing a return/rollback process for RCU-protected data structures is provided that includes checking a user-level state of a preempted thread having a RCU read-side critical section, and executing the critical section of the thread after preemption when the user-level state of the thread indicates execution, otherwise returning to a point of preemption, resuming execution of the thread and disabling checking the user-level state when the user-level state of the thread indicates return.

Abstract: An apparatus, system, and method are disclosed for dynamically allocating main memory among applications. The apparatus includes a cache memory module configured to maintain a first list and a second list, each list having a plurality of pages, and a resize module configured to resize the cache by adaptively selecting the first or second list and subtracting pages from or adding pages to the selected list. The system includes the apparatus and a cache replacement module configured to adaptively distribute a workload between the first list and the second list. The method includes maintaining a first list and a second list, each list having a plurality of pages, maintaining a cache memory module having a selected size, and resizing the selected size by adaptively selecting the first or second list and adding pages to the selected list to increase the selected size and subtracting pages from the selected list to decrease the selected size.

Abstract: A method, system and computer program product for avoiding unnecessary grace period token processing while detecting a grace period without atomic instructions in a read-copy update subsystem or other processing environment that requires deferring removal of a shared data element until pre-existing references to the data element are removed. Detection of the grace period includes establishing a token to be circulated between processing entities sharing access to the data element. A grace period elapses whenever the token makes a round trip through the processing entities. A distributed indicator associated with each processing entity indicates whether there is a need to perform removal processing on any shared data element. The distributed indicator is processed at each processing entity before the latter engages in token processing. Token processing is performed only when warranted by the distributed indicator.

Abstract: A system, method and computer program product for synchronizing updates to shared mutable data in a clustered data processing system. A data element update operation is performed at each node of the cluster while preserving a pre-update view of the shared mutable data, or an associated operational mode, on behalf of readers that may be utilizing the pre-update view. A request is made for detection of a grace period, and grace period detection processing is performed for detecting when the cluster-wide grace period has occurred. When it does, a deferred action associated with the update operation it taken, such as removal of a pre-update view of the data element or termination of an associated mode of operation.

Abstract: A system, method and computer program product for atomically moving a shared list element from a first list location to a second list location includes inserting a placeholder element at the second list location to signify to readers that a move operation is underway, removing the shared list element from the first list location, re-identifying the list element to reflect its move from the first list location to the second list location, inserting it at the second list location and unlinking the placeholder element. A deferred removal of the placeholder element is performed following a period in which readers can no longer maintain references thereto. A method, system and computer program product are additionally provided for performing a lookup of a target list element that is subject to being atomically moved from a first list to a second list.