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Commit c1309d74 authored by Dianne Hackborn's avatar Dianne Hackborn Committed by Alex Ray
Browse files

Add callback hack to find out when to reload system properties. 

Every IBinder object can accept a new transaction to tell it that
it might want to reload system properties, and in the process
anyone can register a callback to be executed when this happens.

Use this to reload the trace property.

This is very much ONLY for debugging.

Change-Id: I55c67c46f8f3fa9073bef0dfaab4577ed1d47eb4
parent 6c1cf1c8

include/utils/Trace.h

+5 −0
Original line number Diff line number Diff line
@@ -121,11 +121,16 @@ private: 
        }

    }



    static void changeCallback();



    // init opens the trace marker file for writing and reads the

    // atrace.tags.enableflags system property.  It does this only the first

    // time it is run, using sMutex for synchronization.

    static void init();



    // retrieve the current value of the system property.

    static void loadSystemProperty();



    // sIsReady is a boolean value indicating whether a call to init() has

    // completed in this process.  It is initialized to 0 and set to 1 when the

    // first init() call completes.  It is set to 1 even if a failure occurred

include/utils/misc.h

+4 −0
Original line number Diff line number Diff line
@@ -88,6 +88,10 @@ void strreverse(char* begin, char* end); 
void k_itoa(int value, char* str, int base);

char* itoa(int val, int base);



typedef void (*sysprop_change_callback)(void);

void add_sysprop_change_callback(sysprop_change_callback cb, int priority);

void report_sysprop_change();



}; // namespace android



#endif // _LIBS_UTILS_MISC_H

libs/utils/Trace.cpp

+18 −4
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include <cutils/properties.h>

#include <utils/Log.h>

#include <utils/Trace.h>

#include <utils/misc.h>



namespace android {
@@ -27,10 +28,19 @@ int Tracer::sTraceFD = -1; 
uint64_t Tracer::sEnabledTags = 0;

Mutex Tracer::sMutex;



void Tracer::changeCallback() {

    Mutex::Autolock lock(sMutex);

    if (sIsReady && sTraceFD >= 0) {

        loadSystemProperty();

    }

}



void Tracer::init() {

    Mutex::Autolock lock(sMutex);



    if (!sIsReady) {

        add_sysprop_change_callback(changeCallback, 0);



        const char* const traceFileName =

                "/sys/kernel/debug/tracing/trace_marker";

        sTraceFD = open(traceFileName, O_WRONLY);
@@ -38,14 +48,18 @@ void Tracer::init() { 
            ALOGE("error opening trace file: %s (%d)", strerror(errno), errno);

            // sEnabledTags remains zero indicating that no tracing can occur

        } else {

            char value[PROPERTY_VALUE_MAX];

            property_get("debug.atrace.tags.enableflags", value, "0");

            sEnabledTags = (strtoll(value, NULL, 0) & ATRACE_TAG_VALID_MASK)

                    | ATRACE_TAG_ALWAYS;

            loadSystemProperty();

        }



        android_atomic_release_store(1, &sIsReady);

    }

}



void Tracer::loadSystemProperty() {

    char value[PROPERTY_VALUE_MAX];

    property_get("debug.atrace.tags.enableflags", value, "0");

    sEnabledTags = (strtoll(value, NULL, 0) & ATRACE_TAG_VALID_MASK)

            | ATRACE_TAG_ALWAYS;

}



} // namespace andoid

libs/utils/misc.cpp

+59 −1
Original line number Diff line number Diff line
@@ -14,10 +14,13 @@ 
 * limitations under the License.

 */



#define LOG_TAG "misc"



//

// Miscellaneous utility functions.

//

#include <utils/misc.h>

#include <utils/Log.h>



#include <sys/stat.h>

#include <string.h>
@@ -25,6 +28,12 @@ 
#include <assert.h>

#include <stdio.h>



#if defined(HAVE_PTHREADS)

# include <pthread.h>

#endif



#include <utils/Vector.h>



using namespace android;



namespace android {
@@ -181,5 +190,54 @@ unsigned int roundUpPower2(unsigned int val) 
    return val;

}



}; // namespace android

struct sysprop_change_callback_info {

    sysprop_change_callback callback;

    int priority;

};



#if defined(HAVE_PTHREADS)

static pthread_mutex_t gSyspropMutex = PTHREAD_MUTEX_INITIALIZER;

static Vector<sysprop_change_callback_info>* gSyspropList = NULL;

#endif



void add_sysprop_change_callback(sysprop_change_callback cb, int priority) {

#if defined(HAVE_PTHREADS)

    pthread_mutex_lock(&gSyspropMutex);

    if (gSyspropList == NULL) {

        gSyspropList = new Vector<sysprop_change_callback_info>();

    }

    sysprop_change_callback_info info;

    info.callback = cb;

    info.priority = priority;

    bool added = false;

    for (size_t i=0; i<gSyspropList->size(); i++) {

        if (priority >= gSyspropList->itemAt(i).priority) {

            gSyspropList->insertAt(info, i);

            added = true;

            break;

        }

    }

    if (!added) {

        gSyspropList->add(info);

    }

    pthread_mutex_unlock(&gSyspropMutex);

#endif

}



void report_sysprop_change() {

#if defined(HAVE_PTHREADS)

    pthread_mutex_lock(&gSyspropMutex);

    Vector<sysprop_change_callback_info> listeners;

    if (gSyspropList != NULL) {

        listeners = *gSyspropList;

    }

    pthread_mutex_unlock(&gSyspropMutex);



    //ALOGI("Reporting sysprop change to %d listeners", listeners.size());

    for (size_t i=0; i<listeners.size(); i++) {

        listeners[i].callback();

    }

#endif

}



}; // namespace android