hprof_cpu.c

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/*
 * @(#)hprof_cpu.c  1.23 10/03/23
 * 
 * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * -Redistribution of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 * 
 * -Redistribution in binary form must reproduce the above copyright notice, 
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 * 
 * Neither the name of Oracle or the names of contributors may 
 * be used to endorse or promote products derived from this software without 
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL 
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST 
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, 
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY 
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 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 * 
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */

#include "hprof.h"

/* This file contains the cpu loop for the option cpu=samples */

/* The cpu_loop thread basically waits for gdata->sample_interval millisecs
 *   then wakes up, and for each running thread it gets their stack trace,
 *   and updates the traces with 'hits'. 
 * 
 * No threads are suspended or resumed, and the thread sampling is in the
 *   file hprof_tls.c, which manages all active threads. The sampling
 *   technique (what is sampled) is also in hprof_tls.c.
 *
 * No adjustments are made to the pause time or sample interval except
 *   by the user via the interval=n option (default is 10ms).
 *
 * This thread can cause havoc when started prematurely or not terminated
 *   properly, see cpu_sample_init() and cpu_term(), and their calls in hprof_init.c.
 *
 * The listener loop (hprof_listener.c) can dynamically turn on or off the
 *  sampling of all or selected threads.
 *
 */

/* Private functions */

static void JNICALL
cpu_loop_function(jvmtiEnv *jvmti, JNIEnv *env, void *p)
{
    int         loop_trip_counter;
    jboolean    cpu_loop_running;
    
    loop_trip_counter          = 0;
    
    rawMonitorEnter(gdata->cpu_loop_lock); {
  gdata->cpu_loop_running = JNI_TRUE;
        cpu_loop_running = gdata->cpu_loop_running;
  /* Notify cpu_sample_init() that we have started */
  rawMonitorNotifyAll(gdata->cpu_loop_lock);
    } rawMonitorExit(gdata->cpu_loop_lock); 

    rawMonitorEnter(gdata->cpu_sample_lock); /* Only waits inside loop let go */

    while ( cpu_loop_running ) {
        
        ++loop_trip_counter;
        
  LOG3("cpu_loop()", "iteration", loop_trip_counter);
       
  /* If a dump is in progress, we pause sampling. */
  rawMonitorEnter(gdata->dump_lock); {
            if (gdata->dump_in_process) {
                gdata->pause_cpu_sampling = JNI_TRUE;
            }
        } rawMonitorExit(gdata->dump_lock);

  /* Check to see if we need to pause sampling (listener_loop command) */
        if (gdata->pause_cpu_sampling) {
            
      /*
             * Pause sampling for now. Reset sample controls if
             * sampling is resumed again.
             */
            
      rawMonitorWait(gdata->cpu_sample_lock, 0);
            
      rawMonitorEnter(gdata->cpu_loop_lock); {
    cpu_loop_running = gdata->cpu_loop_running;
      } rawMonitorExit(gdata->cpu_loop_lock); 
           
      /* Continue the while loop, which will terminate if done. */
      continue;
        }

  /* This is the normal short timed wait before getting a sample */
  rawMonitorWait(gdata->cpu_sample_lock,  (jlong)gdata->sample_interval);

  /* Make sure we really want to continue */
  rawMonitorEnter(gdata->cpu_loop_lock); {
      cpu_loop_running = gdata->cpu_loop_running;
  } rawMonitorExit(gdata->cpu_loop_lock); 

  /* Break out if we are done */
  if ( !cpu_loop_running ) {
      break;
  }
        
  /*
         * If a dump request came in after we checked at the top of
         * the while loop, then we catch that fact here. We
         * don't want to perturb the data that is being dumped so
         * we just ignore the data from this sampling loop.
         */
        rawMonitorEnter(gdata->dump_lock); {
            if (gdata->dump_in_process) {
                gdata->pause_cpu_sampling = JNI_TRUE;
            }
        } rawMonitorExit(gdata->dump_lock);
        
  /* Sample all the threads and update trace costs */
  if ( !gdata->pause_cpu_sampling) {
            tls_sample_all_threads(env);
  }

  /* Check to see if we need to finish */
  rawMonitorEnter(gdata->cpu_loop_lock); {
      cpu_loop_running = gdata->cpu_loop_running;
  } rawMonitorExit(gdata->cpu_loop_lock); 

    }
    rawMonitorExit(gdata->cpu_sample_lock);
    
    rawMonitorEnter(gdata->cpu_loop_lock); {
  /* Notify cpu_sample_term() that we are done. */
  rawMonitorNotifyAll(gdata->cpu_loop_lock);
    } rawMonitorExit(gdata->cpu_loop_lock); 

    LOG2("cpu_loop()", "clean termination");
}

/* External functions */

void
cpu_sample_init(JNIEnv *env)
{
    gdata->cpu_sampling  = JNI_TRUE;

    /* Create the raw monitors needed */
    gdata->cpu_loop_lock = createRawMonitor("HPROF cpu loop lock");
    gdata->cpu_sample_lock = createRawMonitor("HPROF cpu sample lock");
    
    rawMonitorEnter(gdata->cpu_loop_lock); {
  createAgentThread(env, "HPROF cpu sampling thread",
          &cpu_loop_function);
  /* Wait for cpu_loop_function() to notify us it has started. */
  rawMonitorWait(gdata->cpu_loop_lock, 0);
    } rawMonitorExit(gdata->cpu_loop_lock);
}

void
cpu_sample_off(JNIEnv *env, ObjectIndex object_index)
{
    jint count;
    
    count = 1;
    if (object_index != 0) {
        tls_set_sample_status(object_index, 0);
        count = tls_sum_sample_status();
    }
    if ( count == 0 ) {
        gdata->pause_cpu_sampling = JNI_TRUE;
    } else {
        gdata->pause_cpu_sampling = JNI_FALSE;
    }
}

void
cpu_sample_on(JNIEnv *env, ObjectIndex object_index)
{
    if ( gdata->cpu_loop_lock == NULL ) {
  cpu_sample_init(env);
    }
    
    if (object_index == 0) {
        gdata->cpu_sampling             = JNI_TRUE;
        gdata->pause_cpu_sampling       = JNI_FALSE;
    } else {
        jint     count;

        tls_set_sample_status(object_index, 1);
        count = tls_sum_sample_status();
        if ( count > 0 ) {
            gdata->pause_cpu_sampling   = JNI_FALSE;
        }
    }
    
    /* Notify the CPU sampling thread that sampling is on */
    rawMonitorEnter(gdata->cpu_sample_lock); {
  rawMonitorNotifyAll(gdata->cpu_sample_lock);
    } rawMonitorExit(gdata->cpu_sample_lock);
    
}

void
cpu_sample_term(JNIEnv *env)
{
    gdata->pause_cpu_sampling   = JNI_FALSE;
    rawMonitorEnter(gdata->cpu_sample_lock); {
  /* Notify the CPU sampling thread to get out of any sampling Wait */
  rawMonitorNotifyAll(gdata->cpu_sample_lock);
    } rawMonitorExit(gdata->cpu_sample_lock);
    rawMonitorEnter(gdata->cpu_loop_lock); {
  if ( gdata->cpu_loop_running ) {
      gdata->cpu_loop_running = JNI_FALSE;
      /* Wait for cpu_loop_function() thread to tell us it completed. */
      rawMonitorWait(gdata->cpu_loop_lock, 0);
  }
    } rawMonitorExit(gdata->cpu_loop_lock);
}

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