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Diffstat (limited to 'libjava/classpath/java/lang/management/ThreadMXBean.java')
| -rw-r--r-- | libjava/classpath/java/lang/management/ThreadMXBean.java | 497 |
1 files changed, 497 insertions, 0 deletions
diff --git a/libjava/classpath/java/lang/management/ThreadMXBean.java b/libjava/classpath/java/lang/management/ThreadMXBean.java new file mode 100644 index 00000000000..669cb3cd8d2 --- /dev/null +++ b/libjava/classpath/java/lang/management/ThreadMXBean.java @@ -0,0 +1,497 @@ +/* ThreadMXBean.java - Interface for a thread bean + Copyright (C) 2006 Free Software Foundation + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + +package java.lang.management; + +/** + * <p> + * Provides access to information about the threads + * of the virtual machine. An instance of this bean is + * obtained by calling + * {@link ManagementFactory#getThreadMXBean()}. + * </p> + * <p> + * Each thread within the virtual machine is given an + * identifier, which is guaranteed to be unique to a + * particular thread over its lifetime (after which it + * may be reused). The identifier for a thread may be + * obtained by calling {@link java.lang.Thread#getId()}. + * This identifier is used within implementations of this + * interface to obtain information about a particular thread + * (or series of threads, in the case of an array of identifiers). + * </p> + * <p> + * This bean supports some optional behaviour, which all + * virtual machines may not choose to implement. Specifically, + * this includes the monitoring of the CPU time used by a + * thread, and the monitoring of thread contention. The former + * is further subdivided into the monitoring of either just + * the current thread or all threads. The methods + * {@link #isThreadCpuTimeSupported()}, + * {@link #isCurrentThreadCpuTimeSupported()} and + * {@link #isThreadContentionMonitoringSupported()} may be + * used to determine whether or not this functionality is + * supported. + * </p> + * <p> + * Furthermore, both these facilities may be disabled. + * In fact, thread contention monitoring is disabled by + * default, and must be explictly turned on by calling + * the {@link #setThreadContentionMonitoringEnabled(boolean)} + * method. + * </p> + * + * @author Andrew John Hughes (gnu_andrew@member.fsf.org) + * @since 1.5 + */ +public interface ThreadMXBean +{ + + /** + * <p> + * This method obtains a list of threads which are deadlocked + * waiting to obtain monitor ownership. On entering a synchronized + * method of an object, or re-entering it after returning from an + * {@link java.lang.Object#wait()} call, a thread obtains ownership + * of the object's monitor. + * </p> + * <p> + * Deadlocks can occur in this situation if one or more threads end up + * waiting for a monitor, P, while also retaining ownership of a monitor, + * Q, required by the thread that currently owns P. To give a simple + * example, imagine thread A calls a synchronized method, R, obtaining the + * monitor, P. It then sleeps within that method, allowing thread B + * to run, but still retaining ownership of P. B calls another + * synchronized method, S, which causes it to obtain the monitor, Q, + * of a different object. While in that method, it then wants to + * call the original synchronized method, R, called by A. Doing so + * requires ownership of P, which is still held by A. Hence, it + * becomes blocked. + * </p> + * <p> + * A then finishes its sleep, becomes runnable, and is then allowed + * to run, being the only eligible thread in this scenario. A tries + * to call the synchronized method, S. It also gets blocked, because + * B still holds the monitor, Q. Hence, the two threads, A and B, + * are deadlocked, as neither can give up its monitor without first + * obtaining the monitor held by the other thread. + * </p> + * <p> + * Calling this method in this scenario would return the thread IDs + * of A and B. Note that this method is not designed for controlling + * synchronization, but for troubleshooting problems which cause such + * deadlocks; it may be prohibitively expensive to use in normal + * operation. + * </p> + * + * @return an array of thread identifiers, corresponding to threads + * which are currently in a deadlocked situation. + * @throws SecurityException if a security manager exists and + * denies ManagementPermission("monitor"). + */ + long[] findMonitorDeadlockedThreads(); + + /** + * Returns all live thread identifiers at the time of initial + * execution. Some thread identifiers in the returned array + * may refer to terminated threads, if this occurs during the + * lifetime of this method. + * + * @return an array of thread identifiers, corresponding to + * current live threads. + * @throws SecurityException if a security manager exists and + * denies ManagementPermission("monitor"). + */ + long[] getAllThreadIds(); + + /** + * <p> + * Returns the total number of nanoseconds of CPU time + * the current thread has used. This is equivalent to calling + * <code>{@link #getThreadCpuTime()}(Thread.currentThread.getId())</code>. + * </p> + * <p> + * Note that the value is only nanosecond-precise, and not accurate; there + * is no guarantee that the difference between two values is really a + * nanosecond. Also, the value is prone to overflow if the offset + * exceeds 2^63. The use of this method depends on virtual machine + * support for measurement of the CPU time of the current thread, + * and on this functionality being enabled. + * </p> + * + * @return the total number of nanoseconds of CPU time the current + * thread has used, or -1 if CPU time monitoring is disabled. + * @throws UnsupportedOperationException if CPU time monitoring is not + * supported. + * @see #getCurrentThreadUserTime() + * @see #isCurrentThreadCpuTimeSupported() + * @see #isThreadCpuTimeEnabled() + * @see #setThreadCpuTimeEnabled(boolean) + */ + long getCurrentThreadCpuTime(); + + /** + * <p> + * Returns the total number of nanoseconds of CPU time + * the current thread has executed in user mode. This is + * equivalent to calling + * <code>{@link #getThreadUserTime()}(Thread.currentThread.getId())</code>. + * </p> + * <p> + * Note that the value is only nanosecond-precise, and not accurate; there + * is no guarantee that the difference between two values is really a + * nanosecond. Also, the value is prone to overflow if the offset + * exceeds 2^63. The use of this method depends on virtual machine + * support for measurement of the CPU time of the current thread, + * and on this functionality being enabled. + * </p> + * + * @return the total number of nanoseconds of CPU time the current + * thread has executed in user mode, or -1 if CPU time + * monitoring is disabled. + * @throws UnsupportedOperationException if CPU time monitoring is not + * supported. + * @see #getCurrentThreadCpuTime() + * @see #isCurrentThreadCpuTimeSupported() + * @see #isThreadCpuTimeEnabled() + * @see #setThreadCpuTimeEnabled(boolean) + */ + long getCurrentThreadUserTime(); + + /** + * Returns the number of live daemon threads. + * + * @return the number of live daemon threads. + */ + int getDaemonThreadCount(); + + /** + * Returns the peak number of live threads since + * the virtual machine was started or the count + * reset using {@link #resetPeakThreadCount()}. + * + * @return the peak live thread count. + * @see #resetPeakThreadCount() + */ + int getPeakThreadCount(); + + /** + * Returns the number of live threads, including + * both daemon threads and non-daemon threads. + * + * @return the current number of live threads. + */ + int getThreadCount(); + + /** + * <p> + * Returns the total number of nanoseconds of CPU time + * the specified thread has used. + * </p> + * <p> + * Note that the value is only nanosecond-precise, and not accurate; there + * is no guarantee that the difference between two values is really a + * nanosecond. Also, the value is prone to overflow if the offset + * exceeds 2^63. The use of this method depends on virtual machine + * support for measurement of the CPU time of the current thread, + * and on this functionality being enabled. + * </p> + * + * @param id the thread identifier of the thread whose CPU time is being + * monitored. + * @return the total number of nanoseconds of CPU time the specified + * thread has used, or -1 if CPU time monitoring is disabled. + * @throws IllegalArgumentException if <code>id</code> <= 0. + * @throws UnsupportedOperationException if CPU time monitoring is not + * supported. + * @see #getThreadUserTime(long) + * @see #isThreadCpuTimeSupported() + * @see #isThreadCpuTimeEnabled() + * @see #setThreadCpuTimeEnabled(boolean) + */ + long getThreadCpuTime(long id); + + /** + * Returns information on the specified thread without any + * stack trace information. This is equivalent to + * <code>{@link #getThreadInfo}(id, 0)</code>. If the + * identifier specifies a thread which is either non-existant + * or not alive, then the method returns <code>null</code>. + * + * @param id the identifier of the thread to return information + * on. + * @return a {@link ThreadInfo} object pertaining to the specified + * thread, or <code>null</code> if the identifier specifies + * a thread that doesn't exist or is not alive. + * @throws IllegalArgumentException if <code>id</code> <= 0. + * @throws SecurityException if a security manager exists and + * denies ManagementPermission("monitor"). + */ + ThreadInfo getThreadInfo(long id); + + /** + * Returns information on the specified threads without any + * stack trace information. This is equivalent to + * <code>{@link #getThreadInfo}(ids, 0)</code>. If an + * identifier specifies a thread which is either non-existant + * or not alive, then the corresponding element in the returned + * array is <code>null</code>. + * + * @param ids an array of thread identifiers to return information + * on. + * @return an array of {@link ThreadInfo} objects matching the + * specified threads. The corresponding element is + * <code>null</code> if the identifier specifies + * a thread that doesn't exist or is not alive. + * @throws IllegalArgumentException if an identifier in the array is + * <= 0. + * @throws SecurityException if a security manager exists and + * denies ManagementPermission("monitor"). + */ + ThreadInfo[] getThreadInfo(long[] ids); + + /** + * Returns information on the specified thread with + * stack trace information to the supplied depth. If the + * identifier specifies a thread which is either non-existant + * or not alive, then the method returns <code>null</code>. + * A maximum depth of 0 corresponds to an empty stack trace + * (an empty array is returned by the appropriate + * {@link ThreadInfo} method). A maximum depth of + * <code>Integer.MAX_VALUE</code> returns the full stack trace. + * + * @param id the identifier of the thread to return information + * on. + * @param maxDepth the maximum depth of the stack trace. + * Values of 0 or <code>Integer.MAX_VALUE</code> + * correspond to an empty and full stack trace + * respectively. + * @return a {@link ThreadInfo} object pertaining to the specified + * thread, or <code>null</code> if the identifier specifies + * a thread that doesn't exist or is not alive. + * @throws IllegalArgumentException if <code>id</code> <= 0. + * @throws IllegalArgumentException if <code>maxDepth</code> < 0. + * @throws SecurityException if a security manager exists and + * denies ManagementPermission("monitor"). + */ + ThreadInfo getThreadInfo(long id, int maxDepth); + + /** + * Returns information on the specified threads with + * stack trace information to the supplied depth. If an + * identifier specifies a thread which is either non-existant + * or not alive, then the corresponding element in the returned + * array is <code>null</code>. A maximum depth of 0 corresponds + * to an empty stack trace (an empty array is returned by the + * appropriate {@link ThreadInfo} method). A maximum depth of + * <code>Integer.MAX_VALUE</code> returns the full stack trace. + * + * @param ids an array of thread identifiers to return information + * on. + * @param maxDepth the maximum depth of the stack trace. + * Values of 0 or <code>Integer.MAX_VALUE</code> + * correspond to an empty and full stack trace + * respectively. + * @return an array of {@link ThreadInfo} objects matching the + * specified threads. The corresponding element is + * <code>null</code> if the identifier specifies + * a thread that doesn't exist or is not alive. + * @throws IllegalArgumentException if an identifier in the array is + * <= 0. + * @throws IllegalArgumentException if <code>maxDepth</code> < 0. + * @throws SecurityException if a security manager exists and + * denies ManagementPermission("monitor"). + */ + ThreadInfo[] getThreadInfo(long[] ids, int maxDepth); + + /** + * <p> + * Returns the total number of nanoseconds of CPU time + * the specified thread has executed in user mode. + * </p> + * <p> + * Note that the value is only nanosecond-precise, and not accurate; there + * is no guarantee that the difference between two values is really a + * nanosecond. Also, the value is prone to overflow if the offset + * exceeds 2^63. The use of this method depends on virtual machine + * support for measurement of the CPU time of the current thread, + * and on this functionality being enabled. + * </p> + * + * @param id the thread identifier of the thread whose CPU time is being + * monitored. + * @return the total number of nanoseconds of CPU time the specified + * thread has executed in user mode, or -1 if CPU time monitoring + * is disabled. + * @throws IllegalArgumentException if <code>id</code> <= 0. + * @throws UnsupportedOperationException if CPU time monitoring is not + * supported. + * @see #getThreadCpuTime(long) + * @see #isThreadCpuTimeSupported() + * @see #isThreadCpuTimeEnabled() + * @see #setThreadCpuTimeEnabled(boolean) + */ + long getThreadUserTime(long id); + + /** + * Returns the total number of threads that have been + * created and started during the lifetime of the virtual + * machine. + * + * @return the total number of started threads. + */ + long getTotalStartedThreadCount(); + + /** + * Returns true if the virtual machine supports the monitoring + * of the CPU time used by the current thread. This is implied + * by {@link isThreadCpuTimeSupported()} returning true. + * + * @return true if monitoring of the CPU time used by the current + * thread is supported by the virtual machine. + * @see #isThreadCpuTimeEnabled() + * @see #isThreadCpuTimeSupported() + * @see #setThreadCpuTimeEnabled(boolean) + */ + boolean isCurrentThreadCpuTimeSupported(); + + /** + * Returns true if thread contention monitoring is currently + * enabled. + * + * @return true if thread contention monitoring is enabled. + * @throws UnsupportedOperationException if the virtual + * machine does not + * support contention + * monitoring. + * @see #isThreadContentionMonitoringSupported() + * @see #setThreadContentionMonitoringEnabled(boolean) + */ + boolean isThreadContentionMonitoringEnabled(); + + /** + * Returns true if thread contention monitoring is supported + * by the virtual machine. + * + * @return true if thread contention monitoring is supported + * by the virtual machine. + * @see #isThreadContentionMonitoringEnabled() + * @see #setThreadContentionMonitoringEnabled(boolean) + */ + boolean isThreadContentionMonitoringSupported(); + + /** + * Returns true if monitoring of the CPU time used by a thread + * is currently enabled. + * + * @return true if thread CPU time monitoring is enabled. + * @throws UnsupportedOperationException if the virtual + * machine does not + * support CPU time + * monitoring. + * @see #isCurrentThreadCpuTimeSupported() + * @see #isThreadCpuTimeSupported() + * @see #setThreadCpuTimeEnabled(boolean) + */ + boolean isThreadCpuTimeEnabled(); + + /** + * Returns true if the virtual machine supports the monitoring + * of the CPU time used by all threads. This implies + * that {@link isCurrentThreadCpuTimeSupported()} returns true. + * + * @return true if monitoring of the CPU time used by the current + * thread is supported by the virtual machine. + * @see #isCurrentThreadCpuTimeSupported() + * @see #isThreadCpuTimeEnabled() + * @see #setThreadCpuTimeEnabled(boolean) + */ + boolean isThreadCpuTimeSupported(); + + /** + * Resets the peak live thread count to the + * current number of live threads, as returned + * by {@link #getThreadCount()}. + * + * @see #getPeakThreadCount() + * @see #getThreadCount() + * @throws SecurityException if a security manager exists and + * denies ManagementPermission("control"). + */ + void resetPeakThreadCount(); + + /** + * Toggles the monitoring of thread contention. Thread + * contention monitoring is disabled by default. Each + * time contention monitoring is re-enabled, the times + * it maintains are reset. + * + * @param enable true if monitoring should be enabled, + * false if it should be disabled. + * @throws UnsupportedOperationException if the virtual + * machine does not + * support contention + * monitoring. + * @throws SecurityException if a security manager exists and + * denies ManagementPermission("control"). + * @see #isThreadContentionMonitoringEnabled() + * @see #isThreadContentionMonitoringSupported() + */ + void setThreadContentionMonitoringEnabled(boolean enable); + + /** + * Toggles the monitoring of CPU time used by threads. The + * initial setting is dependent on the underlying virtual + * machine. On enabling CPU time monitoring, the virtual + * machine may take any value up to and including the current + * time as the start time for monitoring. + * + * @param enable true if monitoring should be enabled, + * false if it should be disabled. + * @throws UnsupportedOperationException if the virtual + * machine does not + * support CPU time + * monitoring. + * @throws SecurityException if a security manager exists and + * denies ManagementPermission("control"). + * @see #isCurrentThreadCpuTimeSupported() + * @see #isThreadCpuTimeEnabled() + * @see #isThreadCpuTimeSupported() + */ + void setThreadCpuTimeEnabled(boolean enable); + +} |