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();
}
/* Architecture-specific initializations and checks go here */
bool dvmCompilerArchVariantInit(void)
{
int i = 0;
/*
* Then, populate the templateEntryOffsets array with the offsets from the
* the dvmCompilerTemplateStart symbol for each template.
*/
#define JIT_TEMPLATE(X) templateEntryOffsets[i++] = \
(intptr_t) dvmCompiler_TEMPLATE_##X - (intptr_t) dvmCompilerTemplateStart;
#include "../../../template/armv6k-vfp/TemplateOpList.h"
#undef JIT_TEMPLATE
/* Target-specific configuration */
gDvmJit.jitTableSize = 1 << 9; // 512
gDvmJit.jitTableMask = gDvmJit.jitTableSize - 1;
gDvmJit.threshold = 200;
gDvmJit.codeCacheSize = 512*1024;
#if defined(WITH_SELF_VERIFICATION)
/* Force into blocking mode */
gDvmJit.blockingMode = true;
gDvm.nativeDebuggerActive = true;
#endif
/* Codegen-specific assumptions */
assert(OFFSETOF_MEMBER(ClassObject, vtable) < 128 &&
(OFFSETOF_MEMBER(ClassObject, vtable) & 0x3) == 0);
assert(OFFSETOF_MEMBER(ArrayObject, length) < 128 &&
(OFFSETOF_MEMBER(ArrayObject, length) & 0x3) == 0);
assert(OFFSETOF_MEMBER(ArrayObject, contents) < 256);
/* Up to 5 args are pushed on top of FP - sizeofStackSaveArea */
assert(sizeof(StackSaveArea) < 236);
/*
* EA is calculated by doing "Rn + imm5 << 2". Make sure that the last
* offset from the struct is less than 128.
*/
if ((offsetof(Thread, jitToInterpEntries) +
sizeof(struct JitToInterpEntries)) >= 128) {
LOGE("Thread.jitToInterpEntries size overflow");
dvmAbort();
}
/* No method JIT for Thumb backend */
gDvmJit.disableOpt |= (1 << kMethodJit);
// Make sure all threads have current values
dvmJitUpdateThreadStateAll();
return true;
}
/**
* 关闭Jit编译器
*/
void dvmCompilerShutdown(void)
{
void *threadReturn;
/* Disable new translation requests */
/* 关闭新的编译请求 */
gDvmJit.pProfTable = NULL;
gDvmJit.pProfTableCopy = NULL;
dvmJitUpdateThreadStateAll(); /* 更新所有线程状态 */
/*
* 以下代码应该是检测在虚拟机关闭之前等待所有编译工作队列完成
* dvmCompilerDumpStats()函数应该会更新所有工作队列的当前状态
* gDvmJit.compilerQueueLength会随着这个函数进行更新，这个常数
* 即是当前工作队列的数量。
*/
if (gDvm.verboseShutdown ||
gDvmJit.profileMode == kTraceProfilingContinuous) {
dvmCompilerDumpStats();
while (gDvmJit.compilerQueueLength)
sleep(5);
}
/* 如果编译器工作线程存在 */
if (gDvmJit.compilerHandle) {
gDvmJit.haltCompilerThread = true; /* 设置关闭标志为true */
/* 发送关闭信号 */
dvmLockMutex(&gDvmJit.compilerLock);
pthread_cond_signal(&gDvmJit.compilerQueueActivity);
dvmUnlockMutex(&gDvmJit.compilerLock);
/* 关闭compilerThreadStart线程 */
if (pthread_join(gDvmJit.compilerHandle, &threadReturn) != 0)
ALOGW("Compiler thread join failed");
else if (gDvm.verboseShutdown)
ALOGD("Compiler thread has shut down");
}
/* Break loops within the translation cache */
dvmJitUnchainAll();
/*
* NOTE: our current implementatation doesn't allow for the compiler
* thread to be restarted after it exits here. We aren't freeing
* the JitTable or the ProfTable because threads which still may be
* running or in the process of shutting down may hold references to
*
* them.
*/
}
void dvmCompilerShutdown(void)
{
void *threadReturn;
/* Disable new translation requests */
gDvmJit.pProfTable = NULL;
gDvmJit.pProfTableCopy = NULL;
dvmJitUpdateThreadStateAll();
if (gDvm.verboseShutdown ||
gDvmJit.profileMode == kTraceProfilingContinuous) {
dvmCompilerDumpStats();
while (gDvmJit.compilerQueueLength)
sleep(5);
}
if (gDvmJit.compilerHandle) {
gDvmJit.haltCompilerThread = true;
dvmLockMutex(&gDvmJit.compilerLock);
pthread_cond_signal(&gDvmJit.compilerQueueActivity);
dvmUnlockMutex(&gDvmJit.compilerLock);
if (pthread_join(gDvmJit.compilerHandle, &threadReturn) != 0)
ALOGW("Compiler thread join failed");
else if (gDvm.verboseShutdown)
ALOGD("Compiler thread has shut down");
}
/* Break loops within the translation cache */
dvmJitUnchainAll();
/*
* NOTE: our current implementatation doesn't allow for the compiler
* thread to be restarted after it exits here. We aren't freeing
* the JitTable or the ProfTable because threads which still may be
* running or in the process of shutting down may hold references to
* them.
*/
}
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;
}
/**
* @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();
}
