I've got a ZynqU+ that I've built and am running embedded linux on. Everything boots fine, and initially runs fine. One problem though is that I see the ue_count in /sys/devices/system/edac/mc/mc0/ is incremented to 13 (ce_count is 0) every time I boot the board. There are no EDAC messages in dmesg or syslog mentioning encountering an uncorrectable error, and investigating the zynqs DDR module's registers (https://www.xilinx.com/htmldocs/registers/ug1087/ug1087-zynq-ultrascale-registers.html search for "DDRC Module"), the status registers containing CE & UE counts are 0 along with all related registers
Additionally, if I stress the system with a bunch of constant read/write operations just to a temp folder I will eventually (10-30mins) see EDAC errors printed out to the console. This will often be followed by a kernel panic, but if the system does not panic investigating the previous locations above I can see my ce_count, ue_count have incremented, syslog now has EDAC error messages in it, and the Zynq DDRC module's registers contain values where they were 0 before (Interestingly, not the CE & UE count register, that remains 0, perhaps EDAC clears it after reporting it?)
I have tested this build across half a dozen different boards and they are all showing the exact same behavior. I have trouble believing these ECC errors are real because of that, but I'm not really sure what other explanation there could be. Perhaps I miss-configured something in linux?
The 13 ue_count on boot really mystifies me though, how can EDAC increment that without reporting any errors, how can it increment that while the zynq's module that it's registered too does not contain any signs of ECC activity?
Any advice on things to check, diagnostics to perform, experience with ECC errors, or anything really would be helpful, as I'm mostly at a loss on this problem.
I am having some issues with my virtualHBA driver on Windows Server 2016. A ran the HLK crashdump support test. 3 times out of 10 the test passed. In those 3 failing tests, the crashdump hangs at 0% while taking Complete dump, or Kernel dump or minidump.
By kernel debugging my code, I found that the call to ExAllocatePoolWithTag() for buffer allocation never actually returns.
Below is the statement which never returns.
pDeviceExtension->pcmdbuf=(struct mycmdrsp *)ExAllocatePoolWithTag(NonPagedPoolCacheAligned,pcmdqSignalSize,((ULONG)'TA1'));
I searched on the web regarding this. However, all of the found pages are focusing on this function returning NULL which in my case never returns.
Any help on how to move forward would be highly appreciated.
Thanks in advance.
You can't allocate memory in crash dump mode. You're running at HIGH_LEVEL with interrupts disabled and so you're calling this API at the wrong IRQL.
The typical solution for a hardware adapter is to set the RequestedDumpBufferSize in the PORT_CONFIGURATION_INFORMATION structure during the normal HwFindAdapter call. Then when you're called again in crash dump mode you use the CrashDumpRegion field to get your dump buffer allocation. You then need to write your own "crash dump mode only" allocator to allocate buffers out of this memory region.
It's a huge pain, especially given that it's difficult/impossible to know how much memory you're ultimately going to need. I usually calculate some minimal configuration overhead (i.e. 1 channel, 8 I/O requests at a time, etc.) and then add in a registry configurable slush. The only benefit is that the environment is stripped down so you don't need to be in your all singing, all dancing configuration.
Suppose there are two Linux kernel modules.
There is one global pointer that is shared between these two modules.
Module 1 is trying to access this pointer, corrupt this pointer value and exits.
Now Module 2 is trying to access this pointer, which is no longer valid and crashes.
Module 1:
module_function()
{
//corrupt global_ptr
}
module2_function()
{
local_ptr = global_ptr;
//local_ptr corrupted
//Now if local_ptr is accessed, it will crash
}
Can somebody explain, if this scenario is valid and possible?
Then
i) How to debug this problem. That is, how to find out which module is corrupting the pointer?
ii) How to fix this problem so that module2 should never crash?
This is a classic case of use-after-free or use-after-modify kind of bug that generally causes oops, thus tainting the linux kernel with G flag set, resulting in system hang and reboot. You can observe these logs in /var/log/kern.log if you are not able to get dmesg logs due to system hang.
In order to debug such kernel memory pointer corruption issues, you need to Enable Slab Corruption debug in your kernel menuconfig and hence .config. For a quicker reference, the steps to do this are:- make menuconfig ---> Kernel hacking ---> Memory debugging ---> Debug slab memory locations
The design solution for this problem would be to not use global pointers between modules, because you never know which module might get freed first leading to pointer corruption.
Mine is a legacy code and somewhere long time back memory leak was introduced.
I am using
_CrtSetDbgFlag ( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF );
which implicitly calls _CrtDumpMemoryLeaks(); upon termination/exit from anywhere in code. I am aware of the fact that if we call _CrtDumpMemoryLeaks(); explicitly and some global object is there then memory leak will be reported. That is why not calling _CrtDumpMemoryLeaks() directly.
Get memory leaks and since I am using "new' throughout thecode exact line number and file name are not coming (inspite of declaring #define _CRTDBG_MAP_ALLOC). I have 3 options:
1. Use VLD: but it does not report any leaks.
2. Override new operator so that CRT works. But get error that new is redefined. actually since it is a huge code base, some other place has overriden it conflicts are arising
3. Use number in curly braces and use _crtbreakalloc , but that number is not stable across runs. thus cannot use this strategy as well.
Please help me resolve this issue. Any better mem leak detecting tools?? I used Valgrind on Linux as well. It also doesnot report any mem leak. Only CRT debug reports.
About the application
It runs on Windows XP Professional SP2.
It's built with Microsoft Visual C++ 6.0 with Service Pack 6.
It's MFC based.
It uses several external dlls (e.g. Xerces, ZLib or ACE).
It has high performance requirements.
It does a lot of network and hard disk I/O, but it's also cpu intensive.
It has an exception handling mechanism which generates a minidump when an unhandled exception occurs.
UPDATE: It is a highly multithreaded application and we are using mutexes to protect concurrent access (of course, we might be failing at some place...)
Facts about the crash
It only happens on multiprocessor/multicore machines and under heavy loads of work.
It happens at random (neither we nor our client have found a pattern yet) after some some hours running.
We cannot reproduce the crash on our testing lab. It only happens on some production systems (but always in multicore machines)
It always ends up crashing at the same point, although the complete stack is not always the same. Let me add the stack of the crashing thread (obtained using WinDbg, sorry we don't have symbols)
Exception code: c0000005 ACCESS_VIOLATION
Address : 006a85b9
Access Type : write
Access Address : 2e020fff
Fault address: 006a85b9 01:002a75b9 C:\MyDir\MyApplication.exe
ChildEBP RetAddr Args to Child
WARNING: Stack unwind information not available. Following frames may be wrong.
030af6c8 7c9206eb 77bfc3c9 01a80000 00224bc3 MyApplication+0x2a85b9
030af960 7c91e9c0 7c92901b 00000ab4 00000000 ntdll!RtlAllocateHeap+0xeac (FPO: [Non-Fpo])
030af98c 7c9205c8 00000001 00000000 00000000 ntdll!ZwWaitForSingleObject+0xc (FPO: [3,0,0])
030af9c0 7c920551 01a80898 7c92056d 313adfb0 ntdll!RtlpFreeToHeapLookaside+0x22 (FPO: [2,0,4])
030afa8c 4ba3ae96 000307da 00130005 00040012 ntdll!RtlFreeHeap+0x1e9 (FPO: [Non-Fpo])
030afacc 77bfc2e3 0214e384 3087c8d8 02151030 0x4ba3ae96
030afb00 7c91e306 7c80bfc1 00000948 00000001 msvcrt!free+0xc8 (FPO: [Non-Fpo])
030afb20 0042965b 030afcc0 0214d780 02151218 ntdll!ZwReleaseSemaphore+0xc (FPO: [3,0,0])
030afb7c 7c9206eb 02e6c471 02ea0000 00000008 MyApplication+0x2965b
030afe60 7c9205c8 02151248 030aff38 7c920551 ntdll!RtlAllocateHeap+0xeac (FPO: [Non-Fpo])
030afe74 7c92056d 0210bfb8 02151250 02151250 ntdll!RtlpFreeToHeapLookaside+0x22 (FPO: [2,0,4])
030aff38 77bfc2de 01a80000 00000000 77bfc2e3 ntdll!RtlFreeHeap+0x647 (FPO: [Non-Fpo])
7c92056d c5ffffff ce7c94be ff7c94be 00ffffff msvcrt!free+0xc3 (FPO: [Non-Fpo])
7c920575 ff7c94be 00ffffff 12000000 907c94be 0xc5ffffff
7c920579 00ffffff 12000000 907c94be 90909090 0xff7c94be
*** WARNING: Unable to verify checksum for xerces-c_2_7.dll
*** ERROR: Symbol file could not be found. Defaulted to export symbols for xerces-c_2_7.dll -
7c92057d 12000000 907c94be 90909090 8b55ff8b MyApplication+0xbfffff
7c920581 907c94be 90909090 8b55ff8b 08458bec xerces_c_2_7
7c920585 90909090 8b55ff8b 08458bec 04408b66 0x907c94be
7c920589 8b55ff8b 08458bec 04408b66 0004c25d 0x90909090
7c92058d 08458bec 04408b66 0004c25d 90909090 0x8b55ff8b
The address MyApplication+0x2a85b9 corresponds to a call to erase() of a std::list.
What I have tried so far
Reviewing all the code related to the point where the crash ends happening.
Trying to enable pageheap on our testing lab though nothing useful has been found by now.
We have substituted the std::list for a C array and then it crashes in other part of the code (although it is related code, it's not in the code where the old list resided). Coincidentally, now it crashes in another erase, though this time of a std::multiset. Let me copy the stack contained in the dump:
ntdll.dll!_RtlpCoalesceFreeBlocks#16() + 0x124e bytes
ntdll.dll!_RtlFreeHeap#12() + 0x91f bytes
msvcrt.dll!_free() + 0xc3 bytes
MyApplication.exe!006a4fda()
[Frames below may be incorrect and/or missing, no symbols loaded for MyApplication.exe]
MyApplication.exe!0069f305()
ntdll.dll!_NtFreeVirtualMemory#16() + 0xc bytes
ntdll.dll!_RtlpSecMemFreeVirtualMemory#16() + 0x1b bytes
ntdll.dll!_ZwWaitForSingleObject#12() + 0xc bytes
ntdll.dll!_RtlpFreeToHeapLookaside#8() + 0x26 bytes
ntdll.dll!_RtlFreeHeap#12() + 0x114 bytes
msvcrt.dll!_free() + 0xc3 bytes
c5ffffff()
(12-Apr-2010) I've tried to enable heap free checking (using gflags) but it slows down the application a lot...
Possible solutions (that I'm aware of) which cannot be applied
"Migrate the application to a newer compiler": We are working on this but It's not a solution at the moment.
"Enable pageheap (normal or full)": We can't enable pageheap on production machines as this affects performance heavily.
I think that's all I remember now, if I have forgotten something I'll add it asap. If you can give me some hint or propose some possible solution, don't hesitate to answer!
You can try peppering your code with calls to the debug heap checking routines to see if you can locate the corruption closer to the source (you're using the debug CRT to track down this problem, right?):
http://msdn.microsoft.com/en-us/library/aa271695(VS.60).aspx
Use Application Verifier from debugging tools for windows. Sometimes it helps.
Try to set up VS to download OS debug symbols and make sure that OMIT FRAME POINTERS is off in your application. Perhaps stack trace will be informative.
Highly multithreaded
Long time ago I discovered that there is a limit for thread count per process in WinXP. My test snippet could create only few thoursands of thread. The problem was resolved by thread pool.
EDIT:
For my purposes there was enough just to check “Application Verifier” checkbox in gflags.exe. Unfortunately, I have no experience with other options.
As for thread limit, test snippet was simple:
unsigned __stdcall ThreadProc(LPVOID)
{
_tprintf(_T("Thread started\n"));
return 0;
}
int _tmain(int argc, _TCHAR* argv[])
{
while (TRUE)
{
unsigned threadId = 0;
_tprintf(_T("Start thread\n"));
_beginthreadex( NULL, 0, &ThreadProc, NULL, 0, &threadId);
}
return 0;
}
I didn’t wait long this time, but handle count in Task Manager was increasing very fast. My real world application got this effect only in 12 hours. But must say the issue was not in crashing, new threads just not created.
Can you post what exceptions you are getting?
If this is some memory corruption bug, then the crash occurs sometime after the memory corruption, so that will be challenging to track down the root cause. You should:
Travel (or remotely logon) to the production system, install Visual Studio, have .pdb and .map files ready (and windows' symbols as well), attach debugger to the release-build and wait for the crash. Though if you set it up correctly, you can use the minidump file on your dev machine, where you would already have your app and window's symbols setup. Then you can see which free call is throwing, and try to figure out which object is being freed to see if that object is corrupted somehow and nearby objects in memory.
Somehow find a way to reproduce the bug in your office, can you create high enough volumes to duplicate what the customer is doing?
Your posted callstacks don't look particularly illuminating.
Since you are using VS 6 with SP6, then its STL is OK.
Can you tell if the app on the production system is leaking any resources? Running perfmon can help with this.
Another thing, you're not calling new/delete like very frequently from different threads are you? I've found that if you do this fast enough, you'll crash your app rather quickly (did this on XP). I had to replace new/delete calls in my app with VirtualAlloc (windows Virtual Memory API), that worked great for me. Of course, STL could be allocating from the heap as well.
Use a performance profiler that can hook into CPU events, such as VTune. Set it up in sampling mode and tell it to wait for events related to cache line sharing. These are identified by a HITM event from the SNOOP phase.
If you run this on a multi processor machine with a realistic workload then it will find places in your code where there is active contention between threads for a single piece of data. You will need to analyze the profiler hot spots found this way and try to find something that is not being wrapped in an appropriate mutex.
I'm not an expert on CPU architecture or anything, but my understanding is that when the CPUs are about to access a piece of data the system will check if any other CPUs are accessing the same piece of data, this is done by watching the memory fetches and writes coming out of each CPU, a process called snooping. Snooping makes sure that if TWO or more CPUs have the same data in each of their caches that the duplicated copies of the data are removed when one of them is modified. A HIT-Modified event means that the system detected this situation and had to flush one of the CPUs cache lines.
See this document for more information on using VTune like this
http://software.intel.com/en-us/articles/using-intel-vtune-performance-analyzer-events-ratios-optimizing-applications/
I don't have a copy of VTune in front of me right now so maybe this won't work but it seems like the lowest impact way of getting some data. VTune in sampling mode should not cause a lot of problems with performance.
The key here is that this only happens on multiprocessor machines (Cores are the same as processors)
What happens when a threaded program runs on a single processor is that two threads never execute at the same time. The OS has to time-slice each processor to simulate threads.
In a multiprocessor system multiple threads can operate at the same time.
You are probably accessing shared resources from different threads at the same time now.
These resources can be be connections to external systems and even global variables and data structures even Singleton classes.
Unfortunately you now have one of the hardest problems to find.
If you can find the memory being corrupted then you need to find who else is using it on a different thread and then synchronize the memory (Semaphore or CriticalSection).
Unfortunately there is no easy way to find the problem.
You might be able to set the processor affinity temporarily to only run on one processor until you find the problem. See link
http://msdn.microsoft.com/en-us/library/ms684251(VS.85).aspx
Here is a method to set affinity on
For Windows XP/Vista/7, access Affinity by opening the Windows Task Manager (CTL+ALT+DEL, or right-click on Task Bar), select "Processes" tab, right-click the application process you wish to isolate, then select "Set Affinity." Inside the Processor Affinity dialog, un-check the CPU/cores you do not need to use. This effectively isolates that application to the selected CPUs/cores preventing cashe spanning and reducing process-switching and simplifies your ability to supervise CPU/core allocation for multiple programs.
As your second stack trace shows, your application is corrupting the heap. The header of a heap block is written over and thus the crash occurs in the heap manager when coalescing free blocks, or when going through the free list (in the first stack trace).
The code you identified that is currently freeing memory may be a victim of another code overflowing or underflowing a memory block.
The easiest way to debug this kind of crash is to use the debugging help from windows, through pageheap or appverifier, but depending on the application it may slow down too much, or grow the memory usage too high to be usable, which seems to be the case. You may try to use light pageheap, which will have less impact.
You need to identify what part of the application is overflowing. One way to do this is to look at the information contained in the overflown block. If you have a crash in RtlpCoalesceFreeBlocks, I think I remember one of the registers (#esi) is pointing to the start of the corrupted block (I am not on a windows system at the time of this writing and can not check that). Or if you have a dump, using windbg command !heap -a will dump all memory and display corrupted blocks (better log into a file, since the full heap listing can be long). Once corrupted blocks are known, their content may help to identify the code.
Another help can be to enable the stack backtraces (using gflags). This can be done in production as it is lighter than pageheap. It will add some information to heap blocks and may move the crash to another place in your application, but the stack traces will help to identify what code allocated the blocks that are overflowing.
I would focus on getting the issue to happen on a build for which you have proper debugging symbols, at least for your main application. You seem to gloss over this with "sorry we don't have symbols", but when symbols are applied, the stacktraces may show you more information.
What exactly does this mean: "We can't generate symbols because we're linking with a library which doesn't link if we're using them."? This seems odd.