Abstract:
A computer program product, apparatus and method for managing recovery of a link in a multi-tasking multi-processor environment. An exemplary embodiment includes shutting off timers for a failed channel associated with the communications link, storing a loss of link condition in a data structure, disabling communications on the failed channel and sending an external notification of the loss of link condition.

Description:
[0001]    Priority based on U.S. Provisional Patent Application Ser. No. 61/031,315, filed Feb. 25, 2008, and entitled “MULTI-TASKING MULTI-PROCESSOR ENVIRONMENTS OVER INFINIBAND” is claimed, the entire contents of which is incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    The present disclosure relates generally to multi-tasking multi-processor environments, and in particular, to managing recovery of a link in a multi-tasking multi-processor environment. 
         [0004]    2. Description of Background 
         [0005]    When operating a communications link in a multi-tasking multi-processor environment, numerous failures can occur and there are a variety of ways in which the communication link can be/recovered. For example, if a channel needs to be recovered in the existing coupling technologies for multi-tasking multi-processor environment, the operation is supported by dedicated hardware. The hardware link can be reset in order to achieve this Loss of Link operation, often by dropping light or cutting power. 
         [0006]    In the case of the new coupling technology based upon industry standard Infiniband, multiple channels can be emulated across a single physical link. Therefore, there is no hardware assist that can be called upon to aid in the recovery of the communication link. As such, recovery is left up to the firmware, which must be able to handle such recovery on a single channel without impacting the other channels that share the physical link. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    An exemplary embodiment includes a computer program product for managing recovery of a communications link in a multi-tasking multi-processor environment, the computer program product including a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method including shutting off timers for a failed channel associated with the communications link, storing a loss of link condition in a data structure, disabling communications on the failed channel and sending an external notification of the loss of link condition. 
         [0008]    Another exemplary embodiment includes an apparatus for managing recovery of a communications link in a multi-tasking multi-processor environment, the computer program product including a processor performing a method including shutting, off timers for a failed channel, associated with the communications link, storing a loss of link condition in a data structure, disabling communications on the failed channel and sending an external notification of the loss of link condition. 
         [0009]    A further exemplary embodiment includes a method for managing recovery of a communications link in a multi-tasking multi-processor environment, the method including shutting off timers for a failed channel associated with the communications link, storing a loss of link condition in a data structure, disabling communications on the failed channel and sending an external notification of the loss of link condition. 
         [0010]    Other articles of manufacture, apparatuses, and/or methods according to embodiments will be or become apparent to one with skill in the art upon review of the following drawings and detailed description. It is intended that all such additional articles of manufacture, apparatuses, and/or methods be included within this description, be within the scope of the present invention, and be protected by the accompanying claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0012]      FIG. 1A  illustrates an exemplary embodiment of a multi-tasking multi-processor Infiniband system; 
           [0013]      FIG. 1B  illustrates an example of a multi-tasking multi-processor environment; 
           [0014]      FIG. 1C  illustrates an example of a multi-tasking multi-processor environment in accordance with an exemplary embodiment; 
           [0015]      FIG. 1  D illustrates an example of a multi-tasking multi-processor environment in accordance with an exemplary embodiment; 
           [0016]      FIG. 2  is a flow chart of a method for managing recovery of a communications link in a multi-tasking multi-processor environment. 
           [0017]      FIG. 3  depicts one embodiment of an article of manufacture incorporating one or more aspects of the present invention. 
           [0018]    The detailed description explains the preferred embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    In accordance with an aspect of the present invention, the systems, methods and computer program products described herein implement an out-of-band command and control interface to guide the process of managing recovery of a link via loss of link in a multi-tasking multi-processor environment. In exemplary embodiments, in the event of a communication link failure a host system sends a message to a remote partner system to indicate that a channel recovery is required. The code associated with the systems then systematically disconnects the channel resources and ensures that these resources are cleaned up and made available for re-use. Once the aforementioned process is complete, the channel can be brought up again. 
         [0020]      FIG. 1A  illustrates an exemplary embodiment of a multi-tasking multi-processor Infiniband system  100 . The system  100  can include an operating system  105  (e.g., IBM zOS) having a top layer including a relational database  101  a logging facility  102 , a locking facility  103  and a cross system coupling facility (XCF). The operating system  105  can further include a multiple virtual storage (MVS) services layer  107  and a message facility layer  108 . The system  100  can further include a coupling facility (CF)  110  having a CF structures layer  111 , a link subsystem  112  and a message architecture extensions layer  113 . In an exemplary embodiment, a transport layer  115  is disposed between and couples the operating system  105  and the CF  110 . In an exemplary implementation, the transport layer  115  is supported by Infiniband.  FIG. 1B  illustrates an example of a multi-tasking multi-processor environment. The example shows three mainframes A, B, C connected into a two different Parallel Sysplex environments using the previous generation of coupling transports. zOS A, zOS B and zOS F are all tied together through a Coupling Facility (CF 1 ). zOS C and zOS D are tied together through CF 2 . Meanwhile zOS E is a stand alone operating system. In this configuration separate channels are connected through separate adapters in the separate frames. It is appreciated that multiple internal channels  116 ,  117 ,  118  include separate external connections  120 .  FIG. 1C  illustrates an example of a multi-tasking multi-processor environment in accordance with an exemplary embodiment. In this example, multiple internal channels  121 ,  122 ,  123  share the same physical connection  125 .  FIG. 1D  illustrates an example of a multi-tasking multi-processor environment  150  in accordance with an exemplary embodiment. The environment  150  can include one or more channels  155 , each channel including command/response areas  156 , data buffers  157 , receive/send queues  158  and adapters  160  for mapping the channels  155  to ports  161  and ultimately communication links  162 , as discussed further herein. The channels  155  can further include queue pairs  159  as discussed further herein. The system  150  can further include control code  165  having functions including but not limited to: rendezvous  166 , auxiliary queue  167 , channel  168 , discovery  169  and subnet administrator  170 . 
         [0021]    In exemplary embodiments, in a loss of link (LOL) scenario, the recovery is a temporary transition to recover from a problem that could not be corrected in a less intrusive fashion. Therefore, the transition has to be as fast and efficient as possible. Recovery of a channel can result from many different situations, including: timeout of communications across the link as detected by the heartbeat support; a communication error that caused a buffer to go into error; a software bug that compromised the integrity of the communications across the channel; an operating system request to recycle the channel; an operator request to disable the channel; and the remote partner informing the local channel that the channel is going through a loss of link operation. 
         [0022]      FIG. 2  is a flow chart of a method for managing recovery of a communications link in a multi-tasking multi-processor environment. The flow chart provides an overview of the operations that take place in order to disable and clean up the channel so that it is no longer operational. At block  210 , the system  200  shuts off all timers for the channel that is experiencing the communication failure. This operation ensures that no asynchronous timer pops associated with this channel remain to be processed, which could jeopardize the state of the channel. At block  220 , the system  200  determines if the originator of the loss of signal request is local. If the request is local, then the system  200  sends a notification at block  230  to a remote partner that a communication failure has occurred. At block  240 , the system  200  sets the state to loss of link (LOL) in progress for each link control block (LCB). If at block  220 , the request was not local, then the flow proceeds directly to block  240 . At block  250 , the system  200  disables communications for the channel that has failed. At block  260 , the system  200  sends a notification to an I/O processor (or an object broker) of the loss of link. At block  270 , the I/O processor then cleans up the resources for the channel. 
         [0023]    Once the channel has been disabled, the I/O processor (IOP) can conditionally begin to restore the channel to operation, which depends upon the original cause of the loss of link. In an exemplary embodiment, the IOP initializes its control blocks for the channel, and then informs the channel layer to start the hardware dependent initialization. The channel initialization process of ensuring that the control blocks associated with the channel are in their initial state, establishing and connecting the queue pairs for the out of band signaling connection, negotiating buffer counts and sizes, connecting each of the queue pairs associated with data buffers, and then exchanging Node Descriptor (system identification information) ensures that the channel is now clean and ready to resume normal data communications. 
         [0024]    Much of the coordination of this activity resides in the firmware, and involves the auxiliary queue pair. The auxiliary queue pair, or out of band signaling, manages not only the breaking down of the channel (the loss of link operation), but also the entire rebuilding and connecting of the channel across the link. 
         [0025]    Technical effects of exemplary embodiments include the ability to recover a loss of link for existing coupling connections emulated in firmware. A single channel which is multiplexed across a shared physical link is capable of being recovered without in any way impacting the other channels that share the physical connection. 
         [0026]    As described above, embodiments can be embodied in the form of computer-implemented processes and apparatuses for practicing those processes. In exemplary embodiments, the invention is embodied in computer program code executed by one or more network elements. Embodiments include a computer program product  300  as depicted in  FIG. 3  on a computer usable medium  302  with computer program code logic  304  containing instructions embodied in tangible media as an article of manufacture. Exemplary articles of manufacture for computer usable medium  302  may include floppy diskettes, CD-ROMs, hard drives, universal serial bus (USB) flash drives, or any other computer-readable storage medium, wherein, when the computer program code logic  304  is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. Embodiments include computer program code logic  304 , for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code logic  304  is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. When implemented on a general-purpose microprocessor, the computer program code logic  304  segments configure the microprocessor to create specific logic circuits. 
         [0027]    While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.