Patent Application
20060136886
1. Technical Field
The present invention relates to data processing and, in particular, to managing thread resources in a data processing system. Still more particularly, the present invention provides a method, apparatus, and program product for using byte code insertion for interrupting locked threads.
2. Description of Related Art
Multi-threaded applications face several problems. For instance, deadlock is a state where threads compete for resources and wait for each other in a permanent state of stalemate. As a specific example, a first thread may attempt to perform a transaction between resources r1, r2 and a second thread may attempt to perform a transaction between r2, r1. The first thread may acquire a lock on resource r1 while the second thread acquires a lock on resource r2. Thus, each thread waits for the other to release the needed resource.
Another problem facing multi-threaded applications is a race condition. A software race condition occurs when the execution of a program is affected by the order and timing of a thread's execution. When a deadlock or race condition, for example, occurs a thread may become “locked.” In other words, a thread may be in a state of execution for a longer period of time than expected and may remain in that state until interrupted.
However, when a thread is in a race condition or “locked” condition, this state may go unnoticed until a human observer discovers the problem. An administrator may then manually interrupt the thread and restart the application. However, a considerable amount of processing time may be lost in the meantime, which may result in a cost for the customer running the application.
This may also damage the customer's perception of the service provider and may directly result in a loss of income by the service provider. For example, an owner of the server may allow customers to run applications on the server in an e-business data processing environment. The server owner may provide this service to the customer under a service level agreement. Thus, if an application thread gets locked and is not immediately interrupted, the application may not be able to execute an agreed-upon number of transactions and, thus, may not satisfy the service level agreement.
The present invention recognizes the disadvantages of the prior art and provides a thread monitor that identifies and interrupts locked threads. A byte code insertion tool is used to insert timers around classes that are bound to threads. Timers may also be inserted around particular portions of code. When a portion of code, such as a thread, a loop, or a condition block, for example, to be monitored begins, a call is made to a thread monitor to start a timer. If the portion of code ends normally, the timer is removed. If the timer expires, then the thread monitor may interrupt the thread or send a notification to a user so that appropriate action may be taken.
The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:
The present invention provides a method, apparatus and computer program product for monitoring threads and interrupting locked threads. The data processing device may be a single-processor computing device, a multiprocessing data processing system, or a virtual processor environment in which multiple processors and multiple layers of software may be utilized to perform various aspects of the present invention. Therefore, the following
With reference now to the figures,
In the depicted example, server 104 is connected to network 102 along with storage unit 106. In addition, clients 108, 110, and 112 are connected to network 102. These clients 108, 110, and 112 may be, for example, personal computers or network computers. In the depicted example, server 104 provides data, such as boot files, operating system images, and applications to clients 108-112. More particularly, server 104 may run applications for customers. These applications may provide products or services for end users at clients 108, 110, and 112, which are clients to server 104. Network data processing system 100 may include additional servers, clients, and other devices not shown.
In the depicted example, network data processing system 100 is the Internet with network 102 representing a worldwide collection of networks and gateways that use the Transmission Control Protocol/Internet Protocol (TCP/IP) suite of protocols to communicate with one another. At the heart of the Internet is a backbone of high-speed data communication lines between major nodes or host computers, consisting of thousands of commercial, government, educational and other computer systems that route data and messages. Of course, network data processing system 100 also may be implemented as a number of different types of networks, such as for example, an intranet, a local area network (LAN), or a wide area network (WAN).
Referring to
Peripheral component interconnect (PCI) bus bridge 214 connected to I/O bus 212 provides an interface to PCI local bus 216. A number of modems may be connected to PCI local bus 216. Typical PCI bus implementations will support four PCI expansion slots or add-in connectors. Communications links to clients 108-112 in
Additional PCI bus bridges 222 and 224 provide interfaces for additional PCI local buses 226 and 228, from which additional modems or network adapters may be supported. In this manner, data processing system 200 allows connections to multiple network computers. A memory-mapped graphics adapter 230 and hard disk 232 may also be connected to I/O bus 212 as depicted, either directly or indirectly.
Those of ordinary skill in the art will appreciate that the hardware depicted in
The data processing system depicted in
With reference now to
In the depicted example, local area network (LAN) adapter 312, audio adapter 316, keyboard and mouse adapter 320, modem 322, read only memory (ROM) 324, hard disk drive (HDD) 326, CD-ROM driver 330, universal serial bus (USB) ports and other communications ports 332, and PCI/PCIe devices 334 may be connected to ICH 310. PCI/PCIe devices may include, for example, Ethernet adapters, add-in cards, PC cards for notebook computers, etc. PCI uses a cardbus controller, while PCIe does not. ROM 324 may be, for example, a flash binary input/output system (BIOS). Hard disk drive 326 and CD-ROM drive 330 may use, for example, an integrated drive electronics (IDE) or serial advanced technology attachment (SATA) interface. A super I/O (SIO) device 336 may be connected to ICH 310.
An operating system runs on processor 302 and is used to coordinate and provide control of various components within data processing system 300 in
Instructions for the operating system, the object-oriented programming system, and applications or programs are located on storage devices, such as hard disk drive 326, and may be loaded into main memory 304 for execution by processor 302. The processes of the present invention are performed by processor 302 using computer implemented instructions, which may be located in a memory such as, for example, main memory 304, memory 324, or in one or more peripheral devices 326 and 330.
Those of ordinary skill in the art will appreciate that the hardware in
For example, data processing system 300 may be a personal digital assistant (PDA), which is configured with flash memory to provide non-volatile memory for storing operating system files and/or user-generated data. The depicted example in
Returning to
In accordance with a preferred embodiment of the present invention, a thread monitor is provided that identifies and interrupts locked threads. A byte code insertion tool is used to insert timers around application classes that are bound to threads. Timers may also be inserted around particular portions of code. When a portion of code, such as a thread, a loop, or a condition block, for example, to be monitored begins, a call is made to a thread monitor to start a timer. If the portion of code ends normally, the timer is removed. If the timer expires, then the thread monitor may interrupt the thread or send a notification to a user so that appropriate action may be taken.
Runnable interface 410 is part of the Java 2 Standard Edition (J2SE) development kit from Sun Microsystems. J2SE is a software development kit for building mission critical enterprise applications. Any class whose instances are intended to be executed by a thread may implement Runnable interface 410. The class must define a method of no arguments called run ( ). Therefore, since application class 420 in particular implements Runnable interface 410, application class 420 includes code for a run ( ) method.
When an instance of application class 420 is bound to a thread, starting the thread causes the run ( ) method to execute. In an exemplary embodiment of the present invention, byte code insertion tool 460 modifies the run ( ) method to communicate with thread monitor 470 through application programming interface (API) 472. Byte code insertion tool 460 examines the class definition to determine if the class includes any code that might lock the thread. For example, if the methods of application class 420 include any loops, functional invocations, or control structures or conditional blocks, then byte code insertion tool 460 prepends bytes into the code. More specifically, byte code insertion tool 460 may modify the run ( ) method to include instructions 432 to notify thread monitor 470 to start a timer and to include instructions 434 to remove the timer if the thread ends execution before the timer expires.
Alternatively, as illustrated in
At injection time, when an instance of a class is bound to a thread and before the thread is started, byte code insertion tool 460 examines the methods of a class to determine whether timers are to be inserted. This determination may be made using profiles. For example, a class with numerous loops and control structures may require separate, shorter timers for each code portion. On the other hand, a class with function invocations may require a single, longer timer inserted into the run ( ) method, for example. As a further example, a default profile may call for the insertion of a single ten second timer into the run ( ) method. The manner in which byte code insertion tool 460 inserts the timer instructions into application classes
When a thread is started and the inserted instructions indicating that a timer is to be started are encountered, the instructions notify thread monitor 470 to start a timer through API 472. This notification may be made through a procedure call that identifies the thread and the length of time for the timer. Thread monitor 470 starts the timer and associates the timer with the thread. When a timer expires, thread monitor 470 may either interrupt the thread or send notification to a user so that the user may take appropriate action.
Byte code insertion tool 460 may be a component of a virtual machine or runtime environment. In an alternative embodiment, byte code insertion tool 460 may be a helper application that is executed within the runtime environment to analyze classes and insert byte code to modify a class.
As illustrated in
Thread monitor 510 associates timer 532 with application thread 520. Application thread 540 begins execution and, at time T2, encounters code segment 542. At this time, application thread 540 instructs thread monitor 510 to start timer 552. Thread monitor 510 associates timer 552 with application thread 540.
Next, at time T3, timer 532 expires. Thread monitor 510 then determines that application thread 520 may be locked and takes appropriate action. The action to be taken may be determined using a profile. For example, thread monitor 510 may have other information about application thread 520 and may determine based on this information that application thread 520 should be interrupted. Alternatively, thread monitor 510 may send notification to a user so that the user may take appropriate action. In the depicted example, thread monitor 510 interrupts application thread 520 at time T3.
At time T4, code segment 542 completes and application thread 540 encounters an instruction to remove timer 552. Application thread 540 then instructs thread monitor 510 to remove timer 552 using the API of thread monitor 510. Thread monitor 510 then removes timer 552.
At time T5, application thread 540 encounters code segment 544. At this time, application thread 540 instructs thread monitor 510 to start timer 554. Thread monitor 510 associates timer 554 with application thread 540. Then, at time T6, timer 554 expires and thread monitor 510 sends notification to a user so that the user may take appropriate action.
As described above, the byte code insertion tool may use profiles to determine whether timers are to be inserted. For example, the byte code insertion tool may determine whether the class includes function invocations, loops, control structures, or the like. An example profile may dictate that particular code segments may be “wrapped” with timers. On the other hand, another example profile may dictate that threads with function invocations may have a timer inserted into the run ( ) method, for example. If the byte code insertion tool determines that timers are not to be inserted into the class, the thread executes in a normal fashion (block 610) and operation ends.
If the byte code insertion tool determines that timers are to be inserted into the code of the class in block 608, the byte code insertion tool inserts add/remove timer instruction into the class (block 612). A determination is made as to whether execution of the thread terminates (block 616). If execution of the thread terminates, the application thread notifies the thread monitor to remove any timers associated with that thread (block 618) and operation ends. Notification may be made by making a call to the API of the thread monitor, for example.
If execution of the thread does not terminate in block 616, a determination is made as to whether a start timer instruction is encountered (block 620). If a start timer instruction is encountered, the application thread notifies the thread monitor to start a timer (block 622). This notification may also include a timer value. Thereafter, operation returns to block 616 to determine whether execution of the thread terminates.
If a start timer instruction is not encountered in block 620, a determination is made as to whether a remove timer instruction is encountered (block 624). If a remove timer instruction is encountered, the application thread notifies the thread monitor to remove the timer (block 626). Thereafter, operation returns to block 616 to determine whether execution of the thread terminates. At any point during the execution of the application thread, the thread monitor or a user may interrupt execution of the thread. The application thread itself does not perform any express operations to interrupt execution. The application thread assumes that execution will terminate in a normal fashion.
If an exit condition does not exist in block 704, a determination is made as to whether a start timer notification is received from an application thread (block 706). If a start timer notification is received, the thread monitor starts a timer (block 708) and associates the timer with the application thread (block 710). Thereafter, operation returns to block 704 to determine whether an exit condition exists.
If a start timer notification is not received in block 706, a determination is made as to whether a remove timer notification is received from an application thread (block 712). If a remove timer notification is received from an application thread, then the corresponding portion of code completed execution without locking. The thread monitor removes the timer for the thread or portion of code (block 714). Thereafter, operation returns to block 704 to determine whether an exit condition exists.
If a remove timer notification is not received in block 712, a determination is made as to whether a thread monitor timer expires (block 716). If a thread monitor timer does not expire, operation returns to block 704 to determine whether an exit condition exists. If, however, a timer does expire in block 716, then the thread monitor assumes that the thread is in a locked condition. A determination is made as to whether to interrupt the thread (block 718).
If the thread monitor decides not to interrupt the thread, the thread monitor sends notification to a user so that the user may take the appropriate action (block 720). Thereafter, operation returns to block 704 to determine whether an exit condition exists. If the thread monitor decides to interrupt the thread in block 718, the thread monitor interrupts the thread (block 722) and operation returns to block 704 to determine whether an exit condition exists.
Thus, the present invention solves the disadvantages of the prior art by providing a thread monitor that identifies and interrupts locked threads. A byte code insertion tool is used to insert timers around classes that are bound to threads. Timers may also be inserted around particular portions of code. When a portion of code, such as a thread, a loop, or a condition block, for example, to be monitored begins, a call is made to a thread monitor to start a timer. If the portion of code ends normally, the timer is removed. If the timer expires, then the thread monitor may interrupt the thread or send a notification to a user so that appropriate action may be taken.
In the above description, byte code insertion is used to insert timers in an application class to be monitored. However, other techniques to instrument or hook code on the fly may be used to add timers to classes that are to be monitored.
It is important to note that while the present invention has been described in the context of a fully functioning data processing system, those of ordinary skill in the art will appreciate that the processes of the present invention are capable of being distributed in the form of a computer readable medium of instructions and a variety of forms and that the present invention applies equally regardless of the particular type of signal bearing media actually used to carry out the distribution. Examples of computer readable media include recordable-type media, such as a floppy disk, a hard disk drive, a RAM, CD-ROMs, DVD-ROMs, and transmission-type media, such as digital and analog communications links, wired or wireless communications links using transmission forms, such as, for example, radio frequency and light wave transmissions. The computer readable media may take the form of coded formats that are decoded for actual use in a particular data processing system.
The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
