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HP OpenVMS Systemsask the wizard |
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The Question is: I have code that accesses PCI configuration registers but not in a device driver. I use the sys$cmkrnl facility. About every 20-50 times I run the code I crash the system. The crash occurs code around the OpenVMS ioc$write_pci_config entry. I suspect that the problem may be related to the fact that I don't raise IPL in my cmkrnl routine. I have a uni-processor Alpha Server 1000. Can you advise as to how to pursue a solution to this problem? The Answer is : The Wizard finds it extremely difficult to debug system crashes without crash dumps. The first suggestion is to examine the crash dump and see what, exactly, is causing the crash. You will need the listings CD that corresponds to the version of OpenVMS you're running. Examination of the IOC$WRITE_PCI_CONFIG routine shows that it acquires the MCHECK spinlock before calling the platform-specific routine that actually writes PCI configuration registers. When the MCHECK spinlock is acquired, IPL is raised to 31 (decimal). Device drivers generally call routines like IOC$WRITE_PCI_CONFIG from either fork IPL (usually 8, holding the SPL$_IOLOCK8 spinlock) or device IPL (22, holding the device lock). You are probably calling from IPL 0, from process address space. If your crash is caused by a pagefault with IPL too high, then you must (at minimum) lock the relevant code and linkage section into memory before calling your kernel-mode routine. If indeed your problem is related to IPL, this is the most likely cause. If your crash is caused by an invalid exception or similar, then you must examine the crash dump to determine what went wrong. If you are still interested in how to raise IPL, see the LOCK/UNLOCK macros (in LIB.MLB, or [LIB]SYSMAR.MAR if you have the listings) for Macro32 programs, or the sys_lock and sys_unlock macros (in SYS$LIB_C.TLB, or [LIB_H]VMS_MACROS.H) for C programs. It would help to acquire a copy of the "Writing OpenVMS Alpha Device Drivers in C" book, too. Without more information, this is about the best the Wizard can do.
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