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Commit 555f89d8 authored by Dianne Hackborn's avatar Dianne Hackborn
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 161534a3

include/binder/IBinder.h

+1 −0
Original line number Diff line number Diff line
@@ -51,6 +51,7 @@ public: 
        PING_TRANSACTION        = B_PACK_CHARS('_','P','N','G'),

        DUMP_TRANSACTION        = B_PACK_CHARS('_','D','M','P'),

        INTERFACE_TRANSACTION   = B_PACK_CHARS('_', 'N', 'T', 'F'),

        SYSPROPS_TRANSACTION    = B_PACK_CHARS('_', 'S', 'P', 'R'),



        // Corresponds to TF_ONE_WAY -- an asynchronous call.

        FLAG_ONEWAY             = 0x00000001

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/binder/Binder.cpp

+7 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <binder/Binder.h>



#include <utils/Atomic.h>

#include <utils/misc.h>

#include <binder/BpBinder.h>

#include <binder/IInterface.h>

#include <binder/Parcel.h>
@@ -199,6 +200,12 @@ status_t BBinder::onTransact( 
            }

            return dump(fd, args);

        }



        case SYSPROPS_TRANSACTION: {

            report_sysprop_change();

            return NO_ERROR;

        }



        default:

            return UNKNOWN_TRANSACTION;

    }

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