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I was wrong on that point. Upon debugging it I found the stack pointer was deemed bad, because I had context* vs. context** wrong. That we even check the stack pointer is dubious but it is the historical behavior -- I merely made the code to do it far more direct/faster/reliable.<BR>
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- Jay<BR><BR> <BR>> Subject: Re: [M3devel] deadlock in Win32 threads?<BR>> From: hosking@cs.purdue.edu<BR>> Date: Thu, 10 Dec 2009 11:10:58 -0500<BR>> CC: m3devel@elegosoft.com<BR>> To: jay.krell@cornell.edu<BR>> <BR>> The second thread should *not* be inCritical when trying to LockHeap. Are you sure that is the case? As it stands you need to be able to suspend a thread even if it is waiting on the heap lock (i.e., because the collector thread already holds the lock).<BR>> <BR>> On 10 Dec 2009, at 01:59, Jay K wrote:<BR>> <BR>> > Hm. First, what changed is probably the movement of stuff from traced to untraced??<BR>> > Which makes it more efficient and more like pthreads.<BR>> > I might try putting that back.<BR>> > <BR>> > <BR>> > What I have now though, is that in T, Mutex, and Condition, I put an integer field writeToBlahBlah.<BR>> > Every time before Lock(giant), whatever, t, m, c, I have I write to that field.<BR>> > That drastically mitigates this problem and it goes away.<BR>> > <BR>> > <BR>> > However that still leaves me with a similar deadlock.<BR>> > <BR>> > <BR>> > This thread is stuck trying to suspend everyone:<BR>> > <BR>> > 0:000> ~*k<BR>> > . 0 Id: a64.1258 Suspend: 1 Teb: 7ffdf000 Unfrozen<BR>> > ChildEBP RetAddr<BR>> > 0012fd1c 006d033e m3core!RTThread__SuspendOthers+0xdd<BR>> > 0012fd6c 006d02f0 m3core!RTCollector__CollectSomeInStateZero+0x12<BR>> > 0012fd80 006cff87 m3core!RTCollector__CollectSome+0x6e<BR>> > 0012fdc4 006c817c m3core!RTHeapRep__CollectEnough+0x9b<BR>> > 0012fe04 006c7d06 m3core!RTAllocator__AllocTraced+0xd7<BR>> > 0012fe40 006c7348 m3core!RTAllocator__GetOpenArray+0x97<BR>> > 0012fe68 0035dc23 m3core!RTHooks__AllocateOpenArray+0x19<BR>> > <BR>> > <BR>> > This thread is stuck trying to get the heap lock.<BR>> > It is I presume "inCritical" already.<BR>> > <BR>> > <BR>> > 3 Id: a64.1750 Suspend: 2 Teb: 7ffdb000 Unfrozen<BR>> > ChildEBP RetAddr<BR>> > 01c7fb84 7c90df5a ntdll!KiFastSystemCallRet<BR>> > 01c7fb88 7c91b24b ntdll!ZwWaitForSingleObject+0xc<BR>> > 01c7fc10 7c901046 ntdll!RtlpWaitForCriticalSection+0x132<BR>> > 01c7fc18 006ed42d ntdll!RtlEnterCriticalSection+0x46<BR>> > 01c7fc24 006ec15e m3core!ThreadWin32__Lock+0xd<BR>> > 01c7fc3c 006c8176 m3core!RTOS__LockHeap+0x2c<BR>> > 01c7fc7c 006c7d06 m3core!RTAllocator__AllocTraced+0xd1<BR>> > 01c7fcb8 006c7348 m3core!RTAllocator__GetOpenArray+0x97<BR>> > 01c7fce0 00f8c175 m3core!RTHooks__AllocateOpenArray+0x19<BR>> > 01c7fd44 00f8b36e m3ui!WinTrestle__CopyRoots+0x165<BR>> > <BR>> > <BR>> > The first thread has the heap lock, and isn't giving it up:<BR>> > <BR>> > 01ebffec 00000000 kernel32!BaseThreadStart+0x37<BR>> > 0:000> ?? m3core!ThreadWin32__heapLock<BR>> > struct _RTL_CRITICAL_SECTION * 0x00f2b3e0<BR>> > +0x00c OwningThread : 0x00001258<BR>> > <BR>> > <BR>> > Suspending the second thread does work, but it stays inCritical.<BR>> > I'm guessing at some of this.<BR>> > <BR>> > The giant lock is no longer relevant.<BR>> > <BR>> > <BR>> > I don't see why pthreads doesn't behave the same.<BR>> > <BR>> > I'll have to read the code more.<BR>> > <BR>> > Hm. inCritical maybe shouldn't be set actually?<BR>> > I'll dig more.<BR>> > <BR>> > <BR>> > - Jay<BR>> > <BR>> > <BR>> > <BR>> > Subject: Re: [M3devel] deadlock in Win32 threads?<BR>> > From: hosking@cs.purdue.edu<BR>> > Date: Wed, 9 Dec 2009 11:13:03 -0500<BR>> > CC: m3devel@elegosoft.com<BR>> > To: jay.krell@cornell.edu<BR>> > <BR>> > Jay, you're the one closest to the Win32 threading code these days. Hope you can track it down.<BR>> > <BR>> > On 9 Dec 2009, at 09:16, Jay K wrote:<BR>> > <BR>> > Win32.<BR>> > <BR>> > I have a wierd system..but I think the bug is real.<BR>> > In particular I was testing a small threading change on head.<BR>> > How alertable is managed, to remove its write in LockMutex, so I could remove the giant lock there.<BR>> > But I just had the alertable changes.<BR>> > <BR>> > <BR>> > It was hanging starting Juno.<BR>> > So I tried to test release.<BR>> > You can't use head Juno with release m3core...and I didn't rebuild everything. I'll do that.<BR>> > So I patched up release m3core to be binary compatible. (I'll probably check that in.)<BR>> > <BR>> > <BR>> > Juno still hangs.<BR>> > <BR>> > <BR>> > Here is what I see:<BR>> > <BR>> > <BR>> > 0:006> ~*k This funny thing is like gdb's "thread apply all bt".<BR>> > ~ is thread; * is all; k is stack.<BR>> > <BR>> > [edited]<BR>> > <BR>> > <BR>> > 6 Id: 790.b0 Suspend: 1 Teb: 7ffd7000 Unfrozen<BR>> > ChildEBP RetAddr<BR>> > 0234fbe8 7c90df5a ntdll!KiFastSystemCallRet<BR>> > 0234fbec 7c91b24b ntdll!ZwWaitForSingleObject+0xc<BR>> > 0234fc74 7c901046 ntdll!RtlpWaitForCriticalSection+0x132<BR>> > 0234fc7c 006ecb4e ntdll!RtlEnterCriticalSection+0x46<BR>> > 0234fc88 006ebd31 m3core!ThreadWin32__EnterCriticalSection_heap+0xe [c:\dev2\cm3<BR>> > .release_branch_cm3_5_8\m3-libs\m3core\src\thread\win32\threadwin32c.c @ 30]<BR>> > 0234fc9c 006d4a51 m3core!RTOS__LockHeap+0x12 [..\src\thread\WIN32\ThreadWin32.m3<BR>> > @ 960]<BR>> > 0234fcd8 006e92b4 m3core!RTHooks__CheckStoreTraced+0x81 [..\src\runtime\common\R<BR>> > TCollector.m3 @ 2253]<BR>> > 0234fd0c 00faa995 m3core!ThreadWin32__LockMutex+0xe0 [..\src\thread\WIN32\Thread<BR>> > Win32.m3 @ 111]<BR>> > 0234fd30 00fd1fd1 m3ui!VBT__Mark+0x2a [..\src\vbt\VBT.m3 @ 1247]<BR>> > ...<BR>> > <BR>> > <BR>> > 7 Id: 790.b34 Suspend: 1 Teb: 7ffd6000 Unfrozen<BR>> > ChildEBP RetAddr<BR>> > 026dfc5c 7c90df5a ntdll!KiFastSystemCallRet<BR>> > 026dfc60 7c91b24b ntdll!ZwWaitForSingleObject+0xc<BR>> > 026dfce8 7c901046 ntdll!RtlpWaitForCriticalSection+0x132<BR>> > 026dfcf0 006ecb2e ntdll!RtlEnterCriticalSection+0x46<BR>> > 026dfcfc 006e9c33 m3core!ThreadWin32__EnterCriticalSection_giant+0xe [c:\dev2\cm<BR>> > 3.release_branch_cm3_5_8\m3-libs\m3core\src\thread\win32\threadwin32c.c @ 29]<BR>> > 026dfd14 006ec0a1 m3core!Thread__Broadcast+0x12 [..\src\thread\WIN32\ThreadWin32<BR>> > .m3 @ 276]<BR>> > 026dfd30 006d0285 m3core!RTOS__BroadcastHeap+0x55 [..\src\thread\WIN32\ThreadWin<BR>> > 32.m3 @ 995]<BR>> > 026dfd44 006d0039 m3core!RTCollector__CollectorOff+0x94 [..\src\runtime\common\R<BR>> > TCollector.m3 @ 716]<BR>> > 026dfd64 006cfff4 m3core!RTCollector_M3_LINE_663+0x40 [..\src\runtime\common\RTC<BR>> > ollector.m3 @ 666]<BR>> > 026dfda8 006c817c m3core!RTHeapRep__CollectEnough+0x100 [..\src\runtime\common\R<BR>> > TCollector.m3 @ 671]<BR>> > 026dfde8 006c7793 m3core!RTAllocator__AllocTraced+0xd7 [..\src\runtime\common\RT<BR>> > Allocator.m3 @ 364]<BR>> > 026dfe1c 006c728d m3core!RTAllocator__GetTracedObj+0x8c [..\src\runtime\common\R<BR>> > TAllocator.m3 @ 222]<BR>> > 026dfe40 10013797 m3core!RTHooks__AllocateTracedObj+0x15 [..\src\runtime\common\<BR>> > RTAllocator.m3 @ 120]<BR>> > 026dfe7c 1000fde5 juno_compiler!JunoCompileRep__Cmd+0xcf [..\src\JunoCompile.m3<BR>> > @ 987]<BR>> > ...<BR>> > <BR>> > <BR>> > Let's look at two of our important locks:<BR>> > ?? is the C++ expression evaluator -- the "good" expression evaluator.<BR>> > <BR>> > <BR>> > 0:006> ?? m3core!ThreadWin32__giant<BR>> > struct _RTL_CRITICAL_SECTION<BR>> > +0x000 DebugInfo : 0x00156b68 _RTL_CRITICAL_SECTION_DEBUG<BR>> > +0x004 LockCount : 2<BR>> > +0x008 RecursionCount : 1<BR>> > +0x00c OwningThread : 0x000000b0<BR>> > +0x010 LockSemaphore : 0x00000708<BR>> > +0x014 SpinCount : 0<BR>> > <BR>> > <BR>> > 0:006> ?? m3core!ThreadWin32__heap<BR>> > struct _RTL_CRITICAL_SECTION<BR>> > +0x000 DebugInfo : 0x00156ba0 _RTL_CRITICAL_SECTION_DEBUG<BR>> > +0x004 LockCount : 1<BR>> > +0x008 RecursionCount : 1<BR>> > +0x00c OwningThread : 0x00000b34<BR>> > +0x010 LockSemaphore : 0x000006ec<BR>> > +0x014 SpinCount : 0<BR>> > <BR>> > <BR>> > So you can see there is a circularity and deadlock.<BR>> > Thread 6 owns giant lock and is waiting for heap lock.<BR>> > Thread 7 owns heap lock and is waiting for giant lock.<BR>> > <BR>> > <BR>> > This occurs because Win32 LockMutex uses traced references within the giant lock. ?<BR>> > Use of traced references implies a possible need to take the heap lock.<BR>> > Doing darn near anything implies a need to use the giant lock.<BR>> > <BR>> > <BR>> > Any ideas Tony?<BR>> > <BR>> > <BR>> > I'm not crazy or have a messed up tree, right?<BR>> > I mean, now that I've discussed it, the deadlock potential is obviously there, right?<BR>> > <BR>> > <BR>> > Pthreads is safe of course, no giant lock.<BR>> > <BR>> > <BR>> > I was about to remove the giant lock from LockMutex/UnlockMutex.<BR>> > That should help?<BR>> > The giant lock would still remain though.<BR>> > <BR>> > <BR>> > Now, we know that condition variables are implementable well enough on Win32.<BR>> > Either with a giant lock, or how Java does it.<BR>> > Aside: I don't fully understand the Java implementation, but if it works, it is goodness.<BR>> > It has no giant lock. I don't understand how the sequence numbers make it work.<BR>> > <BR>> > <BR>> > However the Modula-3 giant lock implementation..I am trusting Birrel here<BR>> > that it works at ll..doesn't interact well with traced references within its own implementation?<BR>> > Maybe this stuff can be teased apart?<BR>> > <BR>> > <BR>> > Same thing with a coherent (I think) release build:<BR>> > <BR>> > 0:008> ~*k<BR>> > <BR>> > 0 Id: f58.d0 Suspend: 1 Teb: 7ffdf000 Unfrozen<BR>> > ChildEBP RetAddr<BR>> > 0012f5f4 7c90df5a ntdll!KiFastSystemCallRet<BR>> > 0012f5f8 7c91b24b ntdll!ZwWaitForSingleObject+0xc<BR>> > 0012f680 7c901046 ntdll!RtlpWaitForCriticalSection+0x132<BR>> > 0012f688 005ece7e ntdll!RtlEnterCriticalSection+0x46<BR>> > 0012f694 005ec06d m3core!ThreadWin32__EnterCriticalSection_heap+0xe<BR>> > 0012f6a8 005d4ab1 m3core!RTOS__LockHeap+0x12<BR>> > 0012f6e4 005e9434 m3core!RTHooks__CheckStoreTraced+0x81<BR>> > 0012f718 00facedc m3core!ThreadWin32__LockMutex+0xe0<BR>> > 0012f774 00fb0b51 m3ui!VBTClass__Rescreen+0xed<BR>> > <BR>> > ...<BR>> > <BR>> > 7 Id: f58.80 Suspend: 1 Teb: 7ffd9000 Unfrozen<BR>> > ChildEBP RetAddr<BR>> > 0240fc98 7c90df5a ntdll!KiFastSystemCallRet<BR>> > 0240fc9c 7c91b24b ntdll!ZwWaitForSingleObject+0xc<BR>> > 0240fd24 7c901046 ntdll!RtlpWaitForCriticalSection+0x132<BR>> > 0240fd2c 005ece5e ntdll!RtlEnterCriticalSection+0x46<BR>> > 0240fd38 005e9e6c m3core!ThreadWin32__EnterCriticalSection_giant+0xe<BR>> > 0240fd50 005ec3dd m3core!Thread__Broadcast+0x12<BR>> > 0240fd6c 005d02e5 m3core!RTOS__BroadcastHeap+0x55<BR>> > 0240fd80 005d0099 m3core!RTCollector__CollectorOff+0x94<BR>> > <BR>> > <BR>> > 0:008> ?? m3core!ThreadWin32__giant<BR>> > struct _RTL_CRITICAL_SECTION<BR>> > +0x000 DebugInfo : 0x7c97e9c0 _RTL_CRITICAL_SECTION_DEBUG<BR>> > +0x004 LockCount : 5<BR>> > +0x008 RecursionCount : 1<BR>> > +0x00c OwningThread : 0x000000d0<BR>> > +0x010 LockSemaphore : 0x00000700<BR>> > +0x014 SpinCount : 0<BR>> > <BR>> > <BR>> > 0:008> ?? m3core!ThreadWin32__heap<BR>> > struct _RTL_CRITICAL_SECTION<BR>> > +0x000 DebugInfo : 0x7c97e9e0 _RTL_CRITICAL_SECTION_DEBUG<BR>> > +0x004 LockCount : 1<BR>> > +0x008 RecursionCount : 1<BR>> > +0x00c OwningThread : 0x00000080<BR>> > +0x010 LockSemaphore : 0x000006fc<BR>> > +0x014 SpinCount : 0<BR>> > <BR>> > <BR>> > 80 has the heap lock and is trying to get the giant lock<BR>> > D0 has the giant lock and is trying to get the heap lock<BR>> > Because of the use of traced references in LockMutex.<BR>> > <BR>> > <BR>> > - Jay<BR>> > <BR>> > <BR>> > <BR>> <BR> </body>
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