International Business Machines Corporation

Donald Fred Ault

Ernest Scott Bender

Donald W Schmidt

Jeffrey Paul Kubala

Leslie W Wyman

Peter Jeremy Relson

Bernard R Pierce

Gary Stuart Puchkoff

Robert R Rogers

Michael Gary Spiegel

Jose R Castano

Robert J Maddison

David B Emmes

Jeffrey David Aman

Jon K Franks

John Arthur Helmbold

Donna N Dillenberger

David B Petersen

John C Dayka

Harris M Morgenstern

Casper A Scalzi

Kenneth E Plambeck

Danny R Sutherland

Richard Henry Guski

Stephen J Schmandt

Ian Geoffrey Redding

Steven Walkowiak

David R Cardall

Eric Charles Finkelstein

John M Forsythe

Donna N T E Dillenberger

John F Fischer

Eric T Miller

In response to the detection of an external event by the first thread, the first thread sends a quiesce event to each additional thread of the application and suspends execution. The quiesce event may be either a suspension event requesting suspension of the additional threads or a termination event requesting termination of the additional threads. Each additional thread, upon receiving the quiesce event, checks its environment to determine whether it is holding any critical system resource. If the additional thread determines that is not holding any critical system resource and that it is therefore safe to quiesce, the additional thread quiesces. Before quiescing, the last additional thread to quiesce resumes the first thread, which is now free to perform critical operations without interference from the additional threads. If the quiesce type is suspension, the first thread resumes the additional threads upon completing its critical operations, whereupon the application resumes its normal operation.

Quiensce termination/suspension in a multithreaded enviroment

Exemplary embodiments include a system and storage medium for managing computer processing functions in a multi-processor computer environment. The system includes a physical processor, a standard logical processor, an assist logical processor sharing a same logical partition as the standard logical processor, and a single operating system instance associated with the logical partition, the single operating system instance including a switch-to service and a switch-from service. The system also includes a dispatch component managed by the single operating system instance. Upon invoking the switch-to service by standard code, the switch-to service checks to see if an assist logical processor is online and, if so, it updates an integrated assist field of a work element block associated with the task for indicating the task is eligible to be executed on the assist logical processor. The switch-to service also assigns a work queue to the work element block.

Method, system, and storage medium for managing computer processing functions

A method for testing computer programs including defining one or more selected force stop points for a target computer program. For each of the selected force stop points the target computer program is executed in a force stop mode and executed again in a non-force stop mode. Input to execution in the force stop mode includes the selected force stop point. The target program is terminated as a result of execution in the force stop mode when the selected force stop point has been reached. Executing in the force stop mode results in a residual environment. The target computer program is executed in a non-force stop mode in the residual environment. Output from executing in a non-force stop mode includes test result data. For each of the selected force stop points it is determined if the test result data is consistent with expected test results.

Method, system and computer program product for testing computer programs

Exemplary embodiments include a method, system, and storage medium for managing computer processing functions in a multi-processor computer environment that includes a standard logical processor and an assist logical processor, each of which share the same operating system instance within a logical partition. The method includes invoking a switch-to service by standard code. The standard code is running on a standard logical processor and is executing a task. The switch-to service checks to see if an assist logical processor is online, and it if finds one, the switch-to service updates an integrated assist field of a work element block associated with the task and assigns a queue to the work element block. The task is dispatched, in accordance with business rules identified in a system control block, on either of said assist logical processor or said standard logical processor.

A single atomic instruction is used to change up to four disjoint areas in memory concurrently in an extended compare and swap operation, replacing traditional locks for serialization and providing recovery for all queue manipulations. Use count-based responsibility passing is employed so that any number of tasks can read the various message queue chains, concurrent with queue updates being made. A summary queue update sequence number is maintained to provide concurrent chain update detection, so that any number of tasks can add elements to the end, or remove elements from the middle (i.e. any where in the chain) concurrently. Concurrent footprinting is used with chain manipulation, so that all (or none) of the chaining indicators and a footprint are set with a single, non-interruptible instruction, making it possible for recovery to always take the correct action. One such use of concurrent footprinting is the concurrent footprinting of use count changes, while another is the transfer of ownership of message queue control blocks. In a preferred embodiment on an IBM S/390 platform, the Perform Locked Operation (PLO) instruction is used to perform the extended compare and swap operations.

Method and apparatus for serializing a message queue in a multiprocessing environment

A method and apparatus for ensuring that a process interacting with a failing process is notified of the failure of that process. Each process has a unique process identifier (PID) associated with it. Each process optionally has an affinity list containing one or more entries, each of which contains the identifier of a process that is to be notified when the process fails. A process updates the affinity list of a target process (either itself or another process) by calling an affinity service of the operating system (OS) kernel, specifying the type of operation (add or delete), the identifier of the target process, the identifier of the process that is to notified, and the type of event that is to be generated for the process that is to be notified. When a process fails, a process termination service of the OS kernel examines the affinity list of the failing process and, for each entry in the list, generates an event of the specified type for the process specified as to be notified.

Method and apparatus for providing for notification of task termination

In a client/server system, a method and apparatus for handing requests for access to a host resource purportedly on behalf of a client from an untrusted application server that may be capable of operating as a &ldquo;rogue&rdquo; server. Upon receiving a service request from a client, an untrusted application server creates a new thread within its address space for the client and obtains from the security server a client security context, which is anchored to the task control block (TCB) for that thread. The client security context specifies the client and indicates whether the client is an authenticated client or an unauthenticated client. When the application server makes a request for access to a host resource purportedly on behalf of the client, the security server examines the security context created for the requesting thread. If the client security context indicates that the client is an authenticated client, the security server grants access to the host resource if the client specified in the client security context is authorized to make the requested access to the host resource. If the client security context indicates that the client is an authenticated client, the security server grants access to the host resource only if both the client specified in the client security context and the application server are authorized to make the requested access to the host resource.

Method and apparatus for controlling server access to a resource in a client/server system

Segments of storage of a computer system are shared among any number of users at varying virtual addresses. The virtual addresses can be in the same address space or different address spaces. The sharing of a segment of storage is provided by storing the real address of a page table corresponding to the segment of storage to be shared at different virtual addresses. This allows users of the same or different address spaces to share the same segment of storage by referencing the same page table.

Sharing segments of storage by enabling the sharing of page tables

A semaphore for controlling access to a shared resource in an information handling system is implemented using an atomic operation that compares an operand with a comparison value and, if the operand is equal to the comparison value, replaces the compared operand and up to three additional operands with replacement values. The semaphore has a first semaphore field containing a value and a sequence count and a second semaphore field containing a pointer to a queue for the semaphore. The queue has zero or more entries corresponding to waiters for the semaphore, each entry with a next entry having a pointer to that next entry. To implement the semaphore, a previous value of the first semaphore field is saved as a comparison value. A first replacement value containing an incremented sequence count is generated for the first semaphore field as a first operand in accordance with the specified operation. A second replacement value for the second semaphore field and a third replacement value for one of the queue entries are generated as second and third operands if the queue is being modified. The current value of the first semaphore field is thereafter compared with the comparison value including the sequence count to see if the current value matches the comparison value. If it does, then, atomically with the comparing step, the first operand is replaced with the first replacement value and, if the queue is being modified, one or both of the second and third operands are replaced with their corresponding replacement values. If the current value of the first semaphore field does not match the comparison value, the semaphore operation is retried, using a newly saved value of the semaphore field as a comparison value.

Method and apparatus for performing a semaphore operation

In a client/server system, a method and apparatus for a listening daemon to distribute work and client connectivity across multiple processes each supporting multiple threads. Upon receiving a request from a client, a listening daemonaccepts the conversation, thus creating a socket. The listening daemon then does a putwork( ) call which places a work request on a system managed work queue. The work request behaves in a manner very similar to spawn in that it provides for parameters to be passed as well as transfer of ownership of the socket. In the meantime, server processes that are created either manually or by the operating system create multiple threads, which invoke a getwork( ) service to retrieve work requests created by the listening daemon. The getwork( ) service transfers the socket to the calling process and notifies the thread which file descriptors it has inherited. The thread is then able to process the client request and respond directly to the client without requiring an intermediate process to provide the communication link. The present invention allows a server in a client/server system to spread the workload across multiple threads in multiple processes, avoiding the creation of too many processes or too many threads in a single process. The direct transfer of the socket eliminates the unnecessary overhead typically required to rebind a new process to the client application.

Method and apparatus for transferring file descriptors in a multiprocess, multithreaded client/server system

A method and apparatus for controlling the assignment of units of work to workload enclaves in a client/server system in which units of work are organized into enclaves with the units of work in each enclave being managed as a single entity. Incoming work requests are queued for processing by one or more worker threads of one or more server processes. In response to the receipt of an incoming work request, a putwork() service of the operating system kernel defines an workload enclave for the work request and adds the work request to a queue of incoming work requests to enqueue the request. In response to a request from a worker thread for more work, a getwork() service of the operating system kernel removes a work request from the queue to dequeue the request and associates the worker thread with the enclave defined for the request. If a worker thread must create a new unit of work while processing a work request, it calls an appropriate service of the operating system kernel, which creates the new unit of work and associates the new process with the enclave of the worker thread. The worker thread is disassociated from the enclave upon completion of the work request.

Method and apparatus for controlling the assignment of units of work to

A method and system for allocating and freeing storage are provided. The method can be built on top of any existing storage management algorithm. The method is described as being built upon the heap storage algorithm most often associated with the C programming environment. The method operates by breaking all storage requests into a fixed number of pools. Each pool is then managed by three tiers of management. The first tier is a so-called quick pool consisting of storage blocks which have already been used and freed and are managed on a LIFO queue. The second tier is made up of cell pool extents that are carved from the heap and then further subdivided into blocks of the appropriate size for each pool. The third tier is made up of the existing heap management algorithms or any other storage management algorithm. The method relies on atomic hardware instructions for removing blocks from the quick pools and cell extents. The lack of blocking serialization allows this method to provide a high performing storage manager, even in multithreaded applications with a high degree of concurrency in malloc( ) and free( ) requests from the threads. Any storage request of a size beyond the largest pool size is satisfied by use of the old malloc( ) interface.

Method and apparatus for allocating and freeing storage utilizing

A method and apparatus for fully restoring the context of a user program, including program status word (PSW) and CPU register contents, following an asynchronous interrupt. Upon the occurrence of an asynchronous interrupt event, control is transferred from the normally executing part of the user program to an interrupt handler of the operating system kernel. The kernel interrupt handler saves the contents of the CPU registers and PSW as they existed at the time of the interrupt in a save area associated with the user program before transferring control to a signal catcher routine of the user program. When it has finished handling the interrupt, the signal catcher routine restores the previous state of program execution as it existed before the interrupt by storing the address of the save area in a selected register (which may be a general register/access register pair), restoring the contents of the registers other than the selected register containing the address of the save area, and then restoring the contents of the PSW and selected register by using a new Resume Program (RP) instruction. The RP instruction contains an operand field specifying through the selected register the base address of the save area together with offset fields specifying the offsets of the saved contents of the PSW and selected register relative to the beginning of the save area. Upon decoding an RP instruction, the CPU executing the instruction adds the displacement to the base address contained in the specified register to form the beginning address of the save area, to which it adds the specified offsets to access the saved PSW and selected register contents. The current PSW and selected register contents are then restored with the saved contents to fully restore the previous program context and return control to the instruction being executed at the point of interrupt. To ensure system integrity, only those fields of the PSW are restored that could have otherwise been restored by a program operating in problem state.

Method and apparatus for fully restoring a program context following an

A method and apparatus for enabling a listening daemon in a client/server system to execute a specified task on behalf of a user. Upon receiving a user request, the listening daemon sets an environment variable in accordance with the user identity specified in the request and issues a system call to the operating system kernel to spawn the user task specified in the request. In response to the system call, the operating system kernel creates a new address space for the specified user task and creates a security environment for the user task in accordance with the environment variable before starting the user task in the new address space.

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Hyde Park, NY, United States of America

Donald Fred Ault