void dvmCompilerUpdateGlobalState()
{
bool jitActive;
bool jitActivate;
bool needUnchain = false;
/*
* The tableLock might not be initialized yet by the compiler thread if
* debugger is attached from the very beginning of the VM launch. If
* pProfTableCopy is NULL, the lock is not initialized yet and we don't
* need to refresh anything either.
*/
if (gDvmJit.pProfTableCopy == NULL) {
return;
}
/*
* On the first enabling of method tracing, switch the compiler
* into a mode that includes trace support for invokes and returns.
* If there are any existing translations, flush them. NOTE: we
* can't blindly flush the translation cache because this code
* may be executed before the compiler thread has finished
* initialization.
*/
if ((gDvm.activeProfilers != 0) &&
!gDvmJit.methodTraceSupport) {
bool resetRequired;
/*
* compilerLock will prevent new compilations from being
* installed while we are working.
*/
dvmLockMutex(&gDvmJit.compilerLock);
gDvmJit.cacheVersion++; // invalidate compilations in flight
gDvmJit.methodTraceSupport = true;
resetRequired = (gDvmJit.numCompilations != 0);
dvmUnlockMutex(&gDvmJit.compilerLock);
if (resetRequired) {
dvmSuspendAllThreads(SUSPEND_FOR_CC_RESET);
resetCodeCache();
dvmResumeAllThreads(SUSPEND_FOR_CC_RESET);
}
}
dvmLockMutex(&gDvmJit.tableLock);
jitActive = gDvmJit.pProfTable != NULL;
jitActivate = !dvmDebuggerOrProfilerActive();
if (jitActivate && !jitActive) {
gDvmJit.pProfTable = gDvmJit.pProfTableCopy;
} else if (!jitActivate && jitActive) {
gDvmJit.pProfTable = NULL;
needUnchain = true;
}
dvmUnlockMutex(&gDvmJit.tableLock);
if (needUnchain)
dvmJitUnchainAll();
// Make sure all threads have current values
dvmJitUpdateThreadStateAll();
}
/*
* Initiate garbage collection.
*
* NOTES:
* - If we don't hold gDvm.threadListLock, it's possible for a thread to
* be added to the thread list while we work. The thread should NOT
* start executing, so this is only interesting when we start chasing
* thread stacks. (Before we do so, grab the lock.)
*
* We are not allowed to GC when the debugger has suspended the VM, which
* is awkward because debugger requests can cause allocations. The easiest
* way to enforce this is to refuse to GC on an allocation made by the
* JDWP thread -- we have to expand the heap or fail.
*/
void dvmCollectGarbageInternal(const GcSpec* spec)
{
GcHeap *gcHeap = gDvm.gcHeap;
u4 gcEnd = 0;
u4 rootStart = 0 , rootEnd = 0;
u4 dirtyStart = 0, dirtyEnd = 0;
size_t numObjectsFreed, numBytesFreed;
size_t currAllocated, currFootprint;
size_t percentFree;
int oldThreadPriority = INT_MAX;
/* The heap lock must be held.
*/
if (gcHeap->gcRunning) {
LOGW_HEAP("Attempted recursive GC");
return;
}
gcHeap->gcRunning = true;
rootStart = dvmGetRelativeTimeMsec();
dvmSuspendAllThreads(SUSPEND_FOR_GC);
/*
* If we are not marking concurrently raise the priority of the
* thread performing the garbage collection.
*/
if (!spec->isConcurrent) {
oldThreadPriority = os_raiseThreadPriority();
}
if (gDvm.preVerify) {
LOGV_HEAP("Verifying roots and heap before GC");
verifyRootsAndHeap();
}
dvmMethodTraceGCBegin();
/* Set up the marking context.
*/
if (!dvmHeapBeginMarkStep(spec->isPartial)) {
LOGE_HEAP("dvmHeapBeginMarkStep failed; aborting");
dvmAbort();
}
/* Mark the set of objects that are strongly reachable from the roots.
*/
LOGD_HEAP("Marking...");
dvmHeapMarkRootSet();
/* dvmHeapScanMarkedObjects() will build the lists of known
* instances of the Reference classes.
*/
assert(gcHeap->softReferences == NULL);
assert(gcHeap->weakReferences == NULL);
assert(gcHeap->finalizerReferences == NULL);
assert(gcHeap->phantomReferences == NULL);
assert(gcHeap->clearedReferences == NULL);
if (spec->isConcurrent) {
/*
* Resume threads while tracing from the roots. We unlock the
* heap to allow mutator threads to allocate from free space.
*/
dvmClearCardTable();
dvmUnlockHeap();
dvmResumeAllThreads(SUSPEND_FOR_GC);
rootEnd = dvmGetRelativeTimeMsec();
}
/* Recursively mark any objects that marked objects point to strongly.
* If we're not collecting soft references, soft-reachable
* objects will also be marked.
*/
LOGD_HEAP("Recursing...");
dvmHeapScanMarkedObjects();
if (spec->isConcurrent) {
/*
* Re-acquire the heap lock and perform the final thread
* suspension.
*/
dirtyStart = dvmGetRelativeTimeMsec();
dvmLockHeap();
dvmSuspendAllThreads(SUSPEND_FOR_GC);
/*
* As no barrier intercepts root updates, we conservatively
* assume all roots may be gray and re-mark them.
*/
dvmHeapReMarkRootSet();
/*
* With the exception of reference objects and weak interned
* strings, all gray objects should now be on dirty cards.
*/
if (gDvm.verifyCardTable) {
dvmVerifyCardTable();
}
/*
* Recursively mark gray objects pointed to by the roots or by
* heap objects dirtied during the concurrent mark.
*/
dvmHeapReScanMarkedObjects();
}
/*
* All strongly-reachable objects have now been marked. Process
* weakly-reachable objects discovered while tracing.
*/
dvmHeapProcessReferences(&gcHeap->softReferences,
spec->doPreserve == false,
&gcHeap->weakReferences,
&gcHeap->finalizerReferences,
&gcHeap->phantomReferences);
#if defined(WITH_JIT)
/*
* Patching a chaining cell is very cheap as it only updates 4 words. It's
* the overhead of stopping all threads and synchronizing the I/D cache
* that makes it expensive.
*
* Therefore we batch those work orders in a queue and go through them
* when threads are suspended for GC.
*/
dvmCompilerPerformSafePointChecks();
#endif
LOGD_HEAP("Sweeping...");
dvmHeapSweepSystemWeaks();
/*
* Live objects have a bit set in the mark bitmap, swap the mark
* and live bitmaps. The sweep can proceed concurrently viewing
* the new live bitmap as the old mark bitmap, and vice versa.
*/
dvmHeapSourceSwapBitmaps();
if (gDvm.postVerify) {
LOGV_HEAP("Verifying roots and heap after GC");
verifyRootsAndHeap();
}
if (spec->isConcurrent) {
dvmUnlockHeap();
dvmResumeAllThreads(SUSPEND_FOR_GC);
dirtyEnd = dvmGetRelativeTimeMsec();
}
dvmHeapSweepUnmarkedObjects(spec->isPartial, spec->isConcurrent,
&numObjectsFreed, &numBytesFreed);
LOGD_HEAP("Cleaning up...");
dvmHeapFinishMarkStep();
if (spec->isConcurrent) {
dvmLockHeap();
}
LOGD_HEAP("Done.");
/* Now's a good time to adjust the heap size, since
* we know what our utilization is.
*
* This doesn't actually resize any memory;
* it just lets the heap grow more when necessary.
*/
dvmHeapSourceGrowForUtilization();
currAllocated = dvmHeapSourceGetValue(HS_BYTES_ALLOCATED, NULL, 0);
currFootprint = dvmHeapSourceGetValue(HS_FOOTPRINT, NULL, 0);
dvmMethodTraceGCEnd();
LOGV_HEAP("GC finished");
gcHeap->gcRunning = false;
LOGV_HEAP("Resuming threads");
if (spec->isConcurrent) {
/*
* Wake-up any threads that blocked after a failed allocation
* request.
*/
dvmBroadcastCond(&gDvm.gcHeapCond);
}
if (!spec->isConcurrent) {
dvmResumeAllThreads(SUSPEND_FOR_GC);
dirtyEnd = dvmGetRelativeTimeMsec();
/*
* Restore the original thread scheduling priority if it was
* changed at the start of the current garbage collection.
*/
if (oldThreadPriority != INT_MAX) {
os_lowerThreadPriority(oldThreadPriority);
}
}
/*
* Move queue of pending references back into Java.
*/
dvmEnqueueClearedReferences(&gDvm.gcHeap->clearedReferences);
gcEnd = dvmGetRelativeTimeMsec();
percentFree = 100 - (size_t)(100.0f * (float)currAllocated / currFootprint);
if (!spec->isConcurrent) {
u4 markSweepTime = dirtyEnd - rootStart;
u4 gcTime = gcEnd - rootStart;
bool isSmall = numBytesFreed > 0 && numBytesFreed < 1024;
ALOGD("%s freed %s%zdK, %d%% free %zdK/%zdK, paused %ums, total %ums",
spec->reason,
isSmall ? "<" : "",
numBytesFreed ? MAX(numBytesFreed / 1024, 1) : 0,
percentFree,
currAllocated / 1024, currFootprint / 1024,
markSweepTime, gcTime);
} else {
u4 rootTime = rootEnd - rootStart;
u4 dirtyTime = dirtyEnd - dirtyStart;
u4 gcTime = gcEnd - rootStart;
bool isSmall = numBytesFreed > 0 && numBytesFreed < 1024;
ALOGD("%s freed %s%zdK, %d%% free %zdK/%zdK, paused %ums+%ums, total %ums",
spec->reason,
isSmall ? "<" : "",
numBytesFreed ? MAX(numBytesFreed / 1024, 1) : 0,
percentFree,
currAllocated / 1024, currFootprint / 1024,
rootTime, dirtyTime, gcTime);
}
if (gcHeap->ddmHpifWhen != 0) {
LOGD_HEAP("Sending VM heap info to DDM");
dvmDdmSendHeapInfo(gcHeap->ddmHpifWhen, false);
}
if (gcHeap->ddmHpsgWhen != 0) {
LOGD_HEAP("Dumping VM heap to DDM");
dvmDdmSendHeapSegments(false, false);
}
if (gcHeap->ddmNhsgWhen != 0) {
LOGD_HEAP("Dumping native heap to DDM");
dvmDdmSendHeapSegments(false, true);
}
}
static bool compilerThreadStartup(void)
{
JitEntry *pJitTable = NULL;
unsigned char *pJitProfTable = NULL;
JitTraceProfCounters *pJitTraceProfCounters = NULL;
unsigned int i;
if (!dvmCompilerArchInit())
goto fail;
/*
* Setup the code cache if we have not inherited a valid code cache
* from the zygote.
*/
if (gDvmJit.codeCache == NULL) {
if (!dvmCompilerSetupCodeCache())
goto fail;
}
/* Allocate the initial arena block */
if (dvmCompilerHeapInit() == false) {
goto fail;
}
/* Cache the thread pointer */
gDvmJit.compilerThread = dvmThreadSelf();
dvmLockMutex(&gDvmJit.compilerLock);
/* Track method-level compilation statistics */
gDvmJit.methodStatsTable = dvmHashTableCreate(32, NULL);
#if defined(WITH_JIT_TUNING)
gDvm.verboseShutdown = true;
#endif
dvmUnlockMutex(&gDvmJit.compilerLock);
/* Set up the JitTable */
/* Power of 2? */
assert(gDvmJit.jitTableSize &&
!(gDvmJit.jitTableSize & (gDvmJit.jitTableSize - 1)));
dvmInitMutex(&gDvmJit.tableLock);
dvmLockMutex(&gDvmJit.tableLock);
pJitTable = (JitEntry*)
calloc(gDvmJit.jitTableSize, sizeof(*pJitTable));
if (!pJitTable) {
ALOGE("jit table allocation failed");
dvmUnlockMutex(&gDvmJit.tableLock);
goto fail;
}
/*
* NOTE: the profile table must only be allocated once, globally.
* Profiling is turned on and off by nulling out gDvm.pJitProfTable
* and then restoring its original value. However, this action
* is not synchronized for speed so threads may continue to hold
* and update the profile table after profiling has been turned
* off by null'ng the global pointer. Be aware.
*/
pJitProfTable = (unsigned char *)malloc(JIT_PROF_SIZE);
if (!pJitProfTable) {
ALOGE("jit prof table allocation failed");
free(pJitTable);
dvmUnlockMutex(&gDvmJit.tableLock);
goto fail;
}
memset(pJitProfTable, gDvmJit.threshold, JIT_PROF_SIZE);
for (i=0; i < gDvmJit.jitTableSize; i++) {
pJitTable[i].u.info.chain = gDvmJit.jitTableSize;
}
/* Is chain field wide enough for termination pattern? */
assert(pJitTable[0].u.info.chain == gDvmJit.jitTableSize);
/* Allocate the trace profiling structure */
pJitTraceProfCounters = (JitTraceProfCounters*)
calloc(1, sizeof(*pJitTraceProfCounters));
if (!pJitTraceProfCounters) {
ALOGE("jit trace prof counters allocation failed");
free(pJitTable);
free(pJitProfTable);
dvmUnlockMutex(&gDvmJit.tableLock);
goto fail;
}
gDvmJit.pJitEntryTable = pJitTable;
gDvmJit.jitTableMask = gDvmJit.jitTableSize - 1;
gDvmJit.jitTableEntriesUsed = 0;
gDvmJit.compilerHighWater =
COMPILER_WORK_QUEUE_SIZE - (COMPILER_WORK_QUEUE_SIZE/4);
/*
* If the VM is launched with wait-on-the-debugger, we will need to hide
* the profile table here
*/
gDvmJit.pProfTable = dvmDebuggerOrProfilerActive() ? NULL : pJitProfTable;
gDvmJit.pProfTableCopy = pJitProfTable;
gDvmJit.pJitTraceProfCounters = pJitTraceProfCounters;
dvmJitUpdateThreadStateAll();
dvmUnlockMutex(&gDvmJit.tableLock);
/* Signal running threads to refresh their cached pJitTable pointers */
dvmSuspendAllThreads(SUSPEND_FOR_REFRESH);
dvmResumeAllThreads(SUSPEND_FOR_REFRESH);
/* Enable signature breakpoints by customizing the following code */
#if defined(SIGNATURE_BREAKPOINT)
/*
* Suppose one sees the following native crash in the bugreport:
* I/DEBUG ( 1638): Build fingerprint: 'unknown'
* I/DEBUG ( 1638): pid: 2468, tid: 2507 >>> com.google.android.gallery3d
* I/DEBUG ( 1638): signal 11 (SIGSEGV), fault addr 00001400
* I/DEBUG ( 1638): r0 44ea7190 r1 44e4f7b8 r2 44ebc710 r3 00000000
* I/DEBUG ( 1638): r4 00000a00 r5 41862dec r6 4710dc10 r7 00000280
* I/DEBUG ( 1638): r8 ad010f40 r9 46a37a12 10 001116b0 fp 42a78208
* I/DEBUG ( 1638): ip 00000090 sp 4710dbc8 lr ad060e67 pc 46b90682
* cpsr 00000030
* I/DEBUG ( 1638): #00 pc 46b90682 /dev/ashmem/dalvik-jit-code-cache
* I/DEBUG ( 1638): #01 pc 00060e62 /system/lib/libdvm.so
*
* I/DEBUG ( 1638): code around pc:
* I/DEBUG ( 1638): 46b90660 6888d01c 34091dcc d2174287 4a186b68
* I/DEBUG ( 1638): 46b90670 d0052800 68006809 28004790 6b68d00e
* I/DEBUG ( 1638): 46b90680 512000bc 37016eaf 6ea866af 6f696028
* I/DEBUG ( 1638): 46b90690 682a6069 429a686b e003da08 6df1480b
* I/DEBUG ( 1638): 46b906a0 1c2d4788 47806d70 46a378fa 47806d70
*
* Clearly it is a JIT bug. To find out which translation contains the
* offending code, the content of the memory dump around the faulting PC
* can be pasted into the gDvmJit.signatureBreakpoint[] array and next time
* when a similar compilation is being created, the JIT compiler replay the
* trace in the verbose mode and one can investigate the instruction
* sequence in details.
*
* The length of the signature may need additional experiments to determine.
* The rule of thumb is don't include PC-relative instructions in the
* signature since it may be affected by the alignment of the compiled code.
* However, a signature that's too short might increase the chance of false
* positive matches. Using gdbjithelper to disassembly the memory content
* first might be a good companion approach.
*
* For example, if the next 4 words starting from 46b90680 is pasted into
* the data structure:
*/
gDvmJit.signatureBreakpointSize = 4;
gDvmJit.signatureBreakpoint =
malloc(sizeof(u4) * gDvmJit.signatureBreakpointSize);
gDvmJit.signatureBreakpoint[0] = 0x512000bc;
gDvmJit.signatureBreakpoint[1] = 0x37016eaf;
gDvmJit.signatureBreakpoint[2] = 0x6ea866af;
gDvmJit.signatureBreakpoint[3] = 0x6f696028;
/*
* The following log will be printed when a match is found in subsequent
* testings:
*
* D/dalvikvm( 2468): Signature match starting from offset 0x34 (4 words)
* D/dalvikvm( 2468): --------
* D/dalvikvm( 2468): Compiler: Building trace for computeVisibleItems,
* offset 0x1f7
* D/dalvikvm( 2468): 0x46a37a12: 0x0090 add-int v42, v5, v26
* D/dalvikvm( 2468): 0x46a37a16: 0x004d aput-object v13, v14, v42
* D/dalvikvm( 2468): 0x46a37a1a: 0x0028 goto, (#0), (#0)
* D/dalvikvm( 2468): 0x46a3794e: 0x00d8 add-int/lit8 v26, v26, (#1)
* D/dalvikvm( 2468): 0x46a37952: 0x0028 goto, (#0), (#0)
* D/dalvikvm( 2468): 0x46a378ee: 0x0002 move/from16 v0, v26, (#0)
* D/dalvikvm( 2468): 0x46a378f2: 0x0002 move/from16 v1, v29, (#0)
* D/dalvikvm( 2468): 0x46a378f6: 0x0035 if-ge v0, v1, (#10)
* D/dalvikvm( 2468): TRACEINFO (554): 0x46a37624
* Lcom/cooliris/media/GridLayer;computeVisibleItems 0x1f7 14 of 934, 8
* blocks
* :
* :
* D/dalvikvm( 2468): 0x20 (0020): ldr r0, [r5, #52]
* D/dalvikvm( 2468): 0x22 (0022): ldr r2, [pc, #96]
* D/dalvikvm( 2468): 0x24 (0024): cmp r0, #0
* D/dalvikvm( 2468): 0x26 (0026): beq 0x00000034
* D/dalvikvm( 2468): 0x28 (0028): ldr r1, [r1, #0]
* D/dalvikvm( 2468): 0x2a (002a): ldr r0, [r0, #0]
* D/dalvikvm( 2468): 0x2c (002c): blx r2
* D/dalvikvm( 2468): 0x2e (002e): cmp r0, #0
* D/dalvikvm( 2468): 0x30 (0030): beq 0x00000050
* D/dalvikvm( 2468): 0x32 (0032): ldr r0, [r5, #52]
* D/dalvikvm( 2468): 0x34 (0034): lsls r4, r7, #2
* D/dalvikvm( 2468): 0x36 (0036): str r0, [r4, r4]
* D/dalvikvm( 2468): -------- dalvik offset: 0x01fb @ goto, (#0), (#0)
* D/dalvikvm( 2468): L0x0195:
* D/dalvikvm( 2468): -------- dalvik offset: 0x0195 @ add-int/lit8 v26,
* v26, (#1)
* D/dalvikvm( 2468): 0x38 (0038): ldr r7, [r5, #104]
* D/dalvikvm( 2468): 0x3a (003a): adds r7, r7, #1
* D/dalvikvm( 2468): 0x3c (003c): str r7, [r5, #104]
* D/dalvikvm( 2468): -------- dalvik offset: 0x0197 @ goto, (#0), (#0)
* D/dalvikvm( 2468): L0x0165:
* D/dalvikvm( 2468): -------- dalvik offset: 0x0165 @ move/from16 v0, v26,
* (#0)
* D/dalvikvm( 2468): 0x3e (003e): ldr r0, [r5, #104]
* D/dalvikvm( 2468): 0x40 (0040): str r0, [r5, #0]
*
* The "str r0, [r4, r4]" is indeed the culprit of the native crash.
*/
#endif
return true;
fail:
return false;
}
/*
* Sleep in sigwait() until a signal arrives.
*/
static void* signalCatcherThreadStart(void* arg)
{
Thread* self = dvmThreadSelf();
sigset_t mask;
int cc;
UNUSED_PARAMETER(arg);
LOGV("Signal catcher thread started (threadid=%d)\n", self->threadId);
/* set up mask with signals we want to handle */
sigemptyset(&mask);
sigaddset(&mask, SIGQUIT);
sigaddset(&mask, SIGUSR1);
while (true) {
int rcvd;
dvmChangeStatus(self, THREAD_VMWAIT);
/*
* Signals for sigwait() must be blocked but not ignored. We
* block signals like SIGQUIT for all threads, so the condition
* is met. When the signal hits, we wake up, without any signal
* handlers being invoked.
*
* We want to suspend all other threads, so that it's safe to
* traverse their stacks.
*
* When running under GDB we occasionally return with EINTR (e.g.
* when other threads exit).
*/
loop:
cc = sigwait(&mask, &rcvd);
if (cc != 0) {
if (cc == EINTR) {
//LOGV("sigwait: EINTR\n");
goto loop;
}
assert(!"bad result from sigwait");
}
if (!gDvm.haltSignalCatcher) {
LOGI("threadid=%d: reacting to signal %d\n",
dvmThreadSelf()->threadId, rcvd);
}
/* set our status to RUNNING, self-suspending if GC in progress */
dvmChangeStatus(self, THREAD_RUNNING);
if (gDvm.haltSignalCatcher)
break;
if (rcvd == SIGQUIT) {
dvmSuspendAllThreads(SUSPEND_FOR_STACK_DUMP);
dvmDumpLoaderStats("sig");
logThreadStacks();
if (false) {
dvmLockMutex(&gDvm.jniGlobalRefLock);
dvmDumpReferenceTable(&gDvm.jniGlobalRefTable, "JNI global");
dvmUnlockMutex(&gDvm.jniGlobalRefLock);
}
//dvmDumpTrackedAllocations(true);
dvmResumeAllThreads(SUSPEND_FOR_STACK_DUMP);
} else if (rcvd == SIGUSR1) {
#if WITH_HPROF
LOGI("SIGUSR1 forcing GC and HPROF dump\n");
hprofDumpHeap(NULL);
#else
LOGI("SIGUSR1 forcing GC (no HPROF)\n");
dvmCollectGarbage(false);
#endif
} else {
LOGE("unexpected signal %d\n", rcvd);
}
}
return NULL;
}
/*
* Respond to a SIGQUIT by dumping the thread stacks. Optionally dump
* a few other things while we're at it.
*
* Thread stacks can either go to the log or to a file designated for holding
* ANR traces. If we're writing to a file, we want to do it in one shot,
* so we can use a single O_APPEND write instead of contending for exclusive
* access with flock(). There may be an advantage in resuming the VM
* before doing the file write, so we don't stall the VM if disk I/O is
* bottlenecked.
*
* If JIT tuning is compiled in, dump compiler stats as well.
*/
static void handleSigQuit()
{
char* traceBuf = NULL;
size_t traceLen;
dvmSuspendAllThreads(SUSPEND_FOR_STACK_DUMP);
dvmDumpLoaderStats("sig");
if (gDvm.stackTraceFile == NULL) {
/* just dump to log */
DebugOutputTarget target;
dvmCreateLogOutputTarget(&target, ANDROID_LOG_INFO, LOG_TAG);
dvmDumpJniStats(&target);
dvmDumpAllThreadsEx(&target, true);
} else {
/* write to memory buffer */
FILE* memfp = open_memstream(&traceBuf, &traceLen);
if (memfp == NULL) {
ALOGE("Unable to create memstream for stack traces");
traceBuf = NULL; /* make sure it didn't touch this */
/* continue on */
} else {
logThreadStacks(memfp);
fclose(memfp);
}
}
#if defined(WITH_JIT) && defined(WITH_JIT_TUNING)
dvmCompilerDumpStats();
#endif
if (false) dvmDumpTrackedAllocations(true);
dvmResumeAllThreads(SUSPEND_FOR_STACK_DUMP);
if (traceBuf != NULL) {
/*
* We don't know how long it will take to do the disk I/O, so put us
* into VMWAIT for the duration.
*/
ThreadStatus oldStatus = dvmChangeStatus(dvmThreadSelf(), THREAD_VMWAIT);
/*
* Open the stack trace output file, creating it if necessary. It
* needs to be world-writable so other processes can write to it.
*/
int fd = open(gDvm.stackTraceFile, O_WRONLY | O_APPEND | O_CREAT, 0666);
if (fd < 0) {
ALOGE("Unable to open stack trace file '%s': %s",
gDvm.stackTraceFile, strerror(errno));
} else {
ssize_t actual = write(fd, traceBuf, traceLen);
if (actual != (ssize_t) traceLen) {
ALOGE("Failed to write stack traces to %s (%d of %zd): %s",
gDvm.stackTraceFile, (int) actual, traceLen,
strerror(errno));
} else {
ALOGI("Wrote stack traces to '%s'", gDvm.stackTraceFile);
}
close(fd);
}
free(traceBuf);
dvmChangeStatus(dvmThreadSelf(), oldStatus);
}
}
/**
* @brief 更新编译器全局状态
* @note 在"vm/Profile.cpp"中的updateActiveProfilers中被调用
*/
void dvmCompilerUpdateGlobalState()
{
bool jitActive;
bool jitActivate;
bool needUnchain = false;
/*
* The tableLock might not be initialized yet by the compiler thread if
* debugger is attached from the very beginning of the VM launch. If
* pProfTableCopy is NULL, the lock is not initialized yet and we don't
* need to refresh anything either.
*/
/*
* 如果在调试器附加到虚拟机启动器的非常早之前，编译器线程对tableLock
* 并没有初始化完成。这是我们不能更新任何状态。
*/
if (gDvmJit.pProfTableCopy == NULL) {
return;
}
/*
* On the first enabling of method tracing, switch the compiler
* into a mode that includes trace support for invokes and returns.
* If there are any existing translations, flush them. NOTE: we
* can't blindly flush the translation cache because this code
* may be executed before the compiler thread has finished
* initialization.
*/
/*
* 第一次启用函数tracing，转化编译器到保护支持invokes与returns
* 指令的trace格式。如果已经存在了一些编译代码则直接刷入他们到缓存中。
* NOTE：我们不能在编译器线程未初始化完成之前刷入代码
*/
/* activeProfilers 表明 开启profiler */
if ((gDvm.activeProfilers != 0) &&
!gDvmJit.methodTraceSupport) { /* 这里表明第一次启动tracing */
bool resetRequired;
/*
* compilerLock will prevent new compilations from being
* installed while we are working.
*/
dvmLockMutex(&gDvmJit.compilerLock);
/* 增加缓冲版本，无效编译 */
gDvmJit.cacheVersion++; // invalidate compilations in flight
gDvmJit.methodTraceSupport = true; /* 开启 */
resetRequired = (gDvmJit.numCompilations != 0); /* 检测是否重设代码缓冲区*/
dvmUnlockMutex(&gDvmJit.compilerLock);
if (resetRequired) {
dvmSuspendAllThreads(SUSPEND_FOR_CC_RESET);
resetCodeCache(); /* 重新更新代码缓冲区 */
dvmResumeAllThreads(SUSPEND_FOR_CC_RESET);
}
}
dvmLockMutex(&gDvmJit.tableLock);
/* 通过判断pProfTable表判断JIT是否被激活 */
jitActive = gDvmJit.pProfTable != NULL;
jitActivate = !dvmDebuggerOrProfilerActive(); /* 处于调试阶段或者profile开启 */
/* jitActivate为TRUE表明处于调试阶段 */
if (jitActivate && !jitActive) {
gDvmJit.pProfTable = gDvmJit.pProfTableCopy; /* 处于调试获取副本 */
} else if (!jitActivate && jitActive) { /* 处于正常运行 */
gDvmJit.pProfTable = NULL;
needUnchain = true;/* 需要解链操作 */
}
dvmUnlockMutex(&gDvmJit.tableLock);
if (needUnchain) /* 不再调试模式下为TRUE */
dvmJitUnchainAll();
// Make sure all threads have current values
/* 对所有线程设置JitTable表 */
dvmJitUpdateThreadStateAll();
}
