[Gems-users] Ruby Segmentation Fault

[Konstantinos Nikas <knikas@xxxxxxxxxxxxxxxxx>]

Hi all,

we have an 8-core CMP and a transactional workload which only uses 2 
threads. We bind the 2 threads to 2 specific processors (avoiding always 
core 0). When we set XACT_LOG_BUFFER_SIZE=2048 everything works fine. 
For smaller values (0, 256, 1024) though the simulation fails.
At first we used to get the following warning messages :

45936462 2 [2,0] endEscapeAction WARNING escape depth < 1. Depth = 0

Searching the mailing list we came across a post which suggested adding 
a beginEscapeAction() call into hardwareAbort(). We included this in our 
code and the warning messages went away. However, the simulations still 
fail with a segmentation fault. Gdb reported the following :
#0  RegisterState::restoreCheckpoint (this=0x0, m_proc=1) at 
/home/users/anastop/gems/gems-2.1//common/Vector.h:92
#1  0x00002aaab066bc5d in TransactionVersionManager::restartTransaction 
(this=0xa341340, thread=0, xact_level=1) at 
/home/users/anastop/gems/gems-2.1//common/Vector.h:109
#2  0x00002aaab0656b89 in 
TransactionInterfaceManager::restartTransactionCallback (this=0xa341230, 
thread=0) at log_tm/TransactionInterfaceManager.C:751
#3  0x00002aaaad20fb70 in ?? () from 
/home/simics/academic/simics-3.0.31/amd64-linux/lib/sparc-u3.so
#4  0x00002aaaad1aed99 in ?? () from 
/home/simics/academic/simics-3.0.31/amd64-linux/lib/sparc-u3.so
#5  0x00002aaaad1aec9a in ?? () from 
/home/simics/academic/simics-3.0.31/amd64-linux/lib/sparc-u3.so
#6  0x00002b1b49bc2eaf in SIM_continue () from 
/home/simics/academic/simics-3.0.31/amd64-linux/bin/libsimics-common.so
#7  0x00002b1b49b83a9c in ?? () from 
/home/simics/academic/simics-3.0.31/amd64-linux/bin/libsimics-common.so
#8  0x00002b1b4aaf739c in PyCFunction_Call (func=0x2aaaaab26560, 
arg=0x2aaaac9f6a50, kw=0x0) at /home/packages/python-2.4.2 .......
Any ideas? Or suggestions how to debug more efficiently?

Kind regards,

Kostis

PS: A similar situation occurs when we run the same 2 threads on a 
4-core machine. It works fine for XACT_LOG_BUFFER_SIZE=0,256,1024,2048 
and fails for size=32!