Icons for Memory Dump Analysis Patterns (Part 19)
Wednesday, April 7th, 2010Today we introduce an icon for Incorrect Stack Trace pattern:
B/W
Color
- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -
Archive for April 7th, 2010
Crash Dump Analysis Patterns (Part 28b)
Wednesday, April 7th, 2010Previously introduced Coupled Processes pattern involves an active request (or an action) and an active wait for a response (or the action status):
It is illustrated on this simple UML sequence diagram (process timeline represent collective request-response threads):
However, there is so called weak coupling when a process subscribes for notifications. Such threads most of the time are passive and processes are not blocked:
The coupling manifests itself when notifier threads start spiking CPU and bring their share of CPU consumption to the notified threads:
Here is an example of such threads from the forthcoming pattern interaction case study:
5 Id: 61018.dbec Suspend: 1 Teb: 7ffae000 Unfrozen
ChildEBP RetAddr
01e3fa68 7c82787b ntdll!KiFastSystemCallRet
01e3fa6c 77c80a6e ntdll!NtRequestWaitReplyPort+0xc
01e3fab8 77c7fcf0 rpcrt4!LRPC_CCALL::SendReceive+0x230
01e3fac4 77c80673 rpcrt4!I_RpcSendReceive+0x24
01e3fad8 77ce315a rpcrt4!NdrSendReceive+0x2b
01e3fec0 771f4fbd rpcrt4!NdrClientCall2+0x22e
01e3fed8 771f4f60 winsta!RpcWinStationWaitSystemEvent+0x1c
01e3ff20 6582116c winsta!WinStationWaitSystemEvent+0x51
[...]
01e3ffec 00000000 kernel32!BaseThreadStart+0x34
In cases of synchronous notifications if a notified thread is blocked we have an instance of a reversed strong coupling.
- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -