Utilisation de WCT
L’exemple de code suivant illustre l’utilisation de l’API de traversée de chaîne d’attente. Il énumère tous les threads du système et imprime la chaîne d’attente pour chaque thread.
Pour énumérer tous les threads dans le système, exécutez l’exemple sans paramètres. Pour énumérer uniquement les threads d’un processus spécifié, exécutez l’exemple et transmettez l’identificateur de processus en tant que paramètre. L’exemple effectue les étapes suivantes :
- Appelle la fonction RegisterWaitChainCOMCallback pour inscrire les fonctions de rappel COM.
- Appelle la fonction OpenThreadWaitChainSession pour créer la session de chaîne d’attente.
- Appelle la fonction AdjustTokenPrivileges pour activer le privilège SE_DEBUG_NAME.
- Appelle les fonctions EnumProcesses et CreateToolhelp32Snapshot pour énumérer les threads spécifiés.
- Appelle getThreadWaitChain pour récupérer un tableau de structures WAITCHAIN_NODE_INFO qui contiennent les nœuds de la chaîne d’attente.
- Imprime les informations de la chaîne d’attente.
- Appelle la fonction CloseThreadWaitChainSession pour propre la chaîne d’attente.
// Copyright (C) Microsoft. All rights reserved.
/*
* Sample code for the Wait Chain Traversal (WCT) API.
*
* This program enumerates all threads in the system and prints the
* wait chain for each of them. It should be run from an elevated
* command prompt to get results for services.
*
*/
#ifndef UNICODE
#define UNICODE
#endif
#include <windows.h>
#include <wct.h>
#include <psapi.h>
#include <tlhelp32.h>
#include <wchar.h>
#include <stdio.h>
#include <stdlib.h>
#pragma comment(lib, "Psapi.lib")
#pragma comment(lib, "Advapi32.lib")
typedef struct _STR_ARRAY
{
CHAR Desc[32];
} STR_ARRAY;
// Human-readable names for the different synchronization types.
STR_ARRAY STR_OBJECT_TYPE[] =
{
{"CriticalSection"},
{"SendMessage"},
{"Mutex"},
{"Alpc"},
{"Com"},
{"ThreadWait"},
{"ProcWait"},
{"Thread"},
{"ComActivation"},
{"Unknown"},
{"Max"}
};
// Global variable to store the WCT session handle
HWCT g_WctHandle = NULL;
// Global variable to store OLE32.DLL module handle.
HMODULE g_Ole32Hnd = NULL;
//
// Function prototypes
//
void
PrintWaitChain (
__in DWORD ThreadId
);
BOOL
GrantDebugPrivilege ( )
/*++
Routine Description:
Enables the debug privilege (SE_DEBUG_NAME) for this process.
This is necessary if we want to retrieve wait chains for processes
not owned by the current user.
Arguments:
None.
Return Value:
TRUE if this privilege could be enabled; FALSE otherwise.
--*/
{
BOOL fSuccess = FALSE;
HANDLE TokenHandle = NULL;
TOKEN_PRIVILEGES TokenPrivileges;
if (!OpenProcessToken(GetCurrentProcess(),
TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY,
&TokenHandle))
{
printf("Could not get the process token");
goto Cleanup;
}
TokenPrivileges.PrivilegeCount = 1;
if (!LookupPrivilegeValue(NULL,
SE_DEBUG_NAME,
&TokenPrivileges.Privileges[0].Luid))
{
printf("Couldn't lookup SeDebugPrivilege name");
goto Cleanup;
}
TokenPrivileges.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
if (!AdjustTokenPrivileges(TokenHandle,
FALSE,
&TokenPrivileges,
sizeof(TokenPrivileges),
NULL,
NULL))
{
printf("Could not revoke the debug privilege");
goto Cleanup;
}
fSuccess = TRUE;
Cleanup:
if (TokenHandle)
{
CloseHandle(TokenHandle);
}
return fSuccess;
}
BOOL
CheckThreads (
__in DWORD ProcId
)
/*++
Routine Description:
Enumerates all threads (or optionally only threads for one
process) in the system. It the calls the WCT API on each of them.
Arguments:
ProcId--Specifies the process ID to analyze. If '0' all processes
in the system will be checked.
Return Value:
TRUE if processes could be checked; FALSE if a general failure
occurred.
--*/
{
DWORD processes[1024];
DWORD numProcesses;
DWORD i;
// Try to enable the SE_DEBUG_NAME privilege for this process.
// Continue even if this fails--we just won't be able to retrieve
// wait chains for processes not owned by the current user.
if (!GrantDebugPrivilege())
{
printf("Could not enable the debug privilege");
}
// Get a list of all processes currently running.
if (EnumProcesses(processes, sizeof(processes), &numProcesses) == FALSE)
{
printf("Could not enumerate processes");
return FALSE;
}
for (i = 0; i < numProcesses / sizeof(DWORD); i++)
{
HANDLE process;
HANDLE snapshot;
if (processes[i] == GetCurrentProcessId())
{
continue;
}
// If the caller specified a Process ID, check if we have a match.
if (ProcId != 0)
{
if (processes[i] != ProcId)
{
continue;
}
}
// Get a handle to this process.
process = OpenProcess(PROCESS_ALL_ACCESS, FALSE, processes[i]);
if (process)
{
WCHAR file[MAX_PATH];
printf("Process 0x%x - ", processes[i]);
// Retrieve the executable name and print it.
if (GetProcessImageFileName(process, file, ARRAYSIZE(file)) > 0)
{
PCWSTR filePart = wcsrchr(file, L'\\');
if (filePart)
{
filePart++;
}
else
{
filePart = file;
}
printf("%S", filePart);
}
printf("\n----------------------------------\n");
// Get a snapshot of all threads and look for the ones
// from the relevant process
snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, 0);
if (snapshot != INVALID_HANDLE_VALUE)
{
THREADENTRY32 thread;
thread.dwSize = sizeof(thread);
// Walk the thread list and print each wait chain
if (Thread32First(snapshot, &thread))
{
do
{
if (thread.th32OwnerProcessID == processes[i])
{
// Open a handle to this specific thread
HANDLE threadHandle = OpenThread(THREAD_ALL_ACCESS,
FALSE,
thread.th32ThreadID);
if (threadHandle)
{
// Check whether the thread is still running
DWORD exitCode;
GetExitCodeThread(threadHandle, &exitCode);
if (exitCode == STILL_ACTIVE)
{
// Print the wait chain.
PrintWaitChain(thread.th32ThreadID);
}
CloseHandle(threadHandle);
}
}
} while (Thread32Next(snapshot, &thread));
}
CloseHandle(snapshot);
}
CloseHandle(process);
printf("\n");
}
}
return TRUE;
}
void
PrintWaitChain (
__in DWORD ThreadId
)
/*++
Routine Description:
Enumerates all threads (or optionally only threads for one
process) in the system. It the calls the WCT API on each thread.
Arguments:
ThreadId--Specifies the thread ID to analyze.
Return Value:
(none)
--*/
{
WAITCHAIN_NODE_INFO NodeInfoArray[WCT_MAX_NODE_COUNT];
DWORD Count, i;
BOOL IsCycle;
printf("%d: ", ThreadId);
Count = WCT_MAX_NODE_COUNT;
// Make a synchronous WCT call to retrieve the wait chain.
if (!GetThreadWaitChain(g_WctHandle,
NULL,
WCTP_GETINFO_ALL_FLAGS,
ThreadId,
&Count,
NodeInfoArray,
&IsCycle))
{
printf("Error (0X%x)\n", GetLastError());
return;
}
// Check if the wait chain is too big for the array we passed in.
if (Count > WCT_MAX_NODE_COUNT)
{
printf("Found additional nodes %d\n", Count);
Count = WCT_MAX_NODE_COUNT;
}
// Loop over all the nodes returned and print useful information.
for (i = 0; i < Count; i++)
{
switch (NodeInfoArray[i].ObjectType)
{
case WctThreadType:
// A thread node contains process and thread ID.
printf("[%x:%x:%s]->",
NodeInfoArray[i].ThreadObject.ProcessId,
NodeInfoArray[i].ThreadObject.ThreadId,
((NodeInfoArray[i].ObjectStatus == WctStatusBlocked) ? "b" : "r"));
break;
default:
// A synchronization object.
// Some objects have names...
if (NodeInfoArray[i].LockObject.ObjectName[0] != L'\0')
{
printf("[%s:%S]->",
STR_OBJECT_TYPE[NodeInfoArray[i].ObjectType-1].Desc,
NodeInfoArray[i].LockObject.ObjectName);
}
else
{
printf("[%s]->",
STR_OBJECT_TYPE[NodeInfoArray[i].ObjectType-1].Desc);
}
if (NodeInfoArray[i].ObjectStatus == WctStatusAbandoned)
{
printf("<abandoned>");
}
break;
}
}
printf("[End]");
// Did we find a deadlock?
if (IsCycle)
{
printf(" !!!Deadlock!!!");
}
printf("\n");
}
void
Usage ()
/*++
Routine Description:
Print usage information to stdout.
--*/
{
printf("\nPrints the thread wait chains for one or all processes in the system.\n\n");
printf("\nUsage:\tWctEnum [ProcId]\n");
printf("\t (no params) -- get the wait chains for all processes\n");
printf("\t ProcId -- get the wait chains for the specified process\n\n");
}
BOOL
InitCOMAccess ()
/*++
Routine Description:
Register COM interfaces with WCT. This enables WCT to provide wait
information if a thread is blocked on a COM call.
--*/
{
PCOGETCALLSTATE CallStateCallback;
PCOGETACTIVATIONSTATE ActivationStateCallback;
// Get a handle to OLE32.DLL. You must keep this handle around
// for the life time for any WCT session.
g_Ole32Hnd = LoadLibrary(L"ole32.dll");
if (!g_Ole32Hnd)
{
printf("ERROR: GetModuleHandle failed: 0x%X\n", GetLastError());
return FALSE;
}
// Retrieve the function addresses for the COM helper APIs.
CallStateCallback = (PCOGETCALLSTATE)
GetProcAddress(g_Ole32Hnd, "CoGetCallState");
if (!CallStateCallback)
{
printf("ERROR: GetProcAddress failed: 0x%X\n", GetLastError());
return FALSE;
}
ActivationStateCallback = (PCOGETACTIVATIONSTATE)
GetProcAddress(g_Ole32Hnd, "CoGetActivationState");
if (!ActivationStateCallback)
{
printf("ERROR: GetProcAddress failed: 0x%X\n", GetLastError());
return FALSE;
}
// Register these functions with WCT.
RegisterWaitChainCOMCallback(CallStateCallback,
ActivationStateCallback);
return TRUE;
}
int _cdecl
wmain (
__in int argc,
__in_ecount(argc) PWSTR* argv
)
/*++
Routine Description:
Main entry point for this application.
--*/
{
int rc = 1;
// Initialize the WCT interface to COM. Continue if this
// fails--there just will not be COM information.
if (!InitCOMAccess())
{
printf("Could not enable COM access\n");
}
// Open a synchronous WCT session.
g_WctHandle = OpenThreadWaitChainSession(0, NULL);
if (NULL == g_WctHandle)
{
printf("ERROR: OpenThreadWaitChainSession failed\n");
goto Cleanup;
}
if (argc < 2)
{
// Enumerate all threads in the system.
CheckThreads(0);
}
else
{
// Only enumerate threads in the specified process.
//
// Take the first command line parameter as the process ID.
DWORD ProcId = 0;
ProcId = _wtoi(argv[1]);
if (ProcId == 0)
{
Usage();
goto Cleanup;
}
CheckThreads(ProcId);
}
// Close the WCT session.
CloseThreadWaitChainSession(g_WctHandle);
rc = 0;
Cleanup:
if (NULL != g_Ole32Hnd)
{
FreeLibrary(g_Ole32Hnd);
}
return rc;
}
Rubriques connexes
Wait Chain Traversal, RÉFÉRENCE WCT, MSDN Magazine 2007 juillet - Bugslayer: Wait Chain Traversal, Support Microsoft: Résoudre les problèmes liés aux applications du Microsoft Store