Linux

Hi,

I am currently working with threads using linux 2.6.11 and glibc 2.3.5 on x86. When i am trying to create thread with user defined stacks glibc gives segmentation fault. I have written a wrapper to pthread_create () and generated shared object for the same. When i am trying to create any thread (for user defined stack) using this shared object i am getting segmentation fault. If i don't create shared object and try to create thread (with user defined stack) using same code, it works fine. I am not able to understand this behavior. Why creating a thread using shared object shall result in segfault. And how to overcome this situation.

NOTE: I got same behavior when tried with linux 2.6.12 and glibc-2.3.6 on arm platform.


gdb output for the behavior is :

Loaded symbols for /lib/libgcc_s.so.1
#0 0x0018a777 in memset () from /lib/libc.so.6
(gdb) bt'
#0 0x0018a777 in memset () from /lib/libc.so.6
No symbol table info available.
#1 0x003e27ef in pthread_create@@GLIBC_2.1 () from /lib/libpthread.so.0
No symbol table info available.
#2 0x003e29fd in pthread_create@GLIBC_2.0 () from /lib/libpthread.so.0
No symbol table info available.
#3 0x00ed9880 in process_create (entry_point=0x8048f4c <ThreadEntryPoint>, pArg=0x1, pStack=0x82e08a8, ulStack_Size=16384, ulPrio=127)
at multithreading.c:1916
stThAttr = {__size = "c\000\000\000\002\000\000\000j\000\000\000\000\02 0\000\000¨H.\b\000@", '\0' <repeats 13 times>, __align = 99}
stSchedParam = {__sched_priority = 99}
pstTd = (ThreadData_t *) 0xedd7d8
state = 0
chPriority = 99 'c'
ulRetVal = 0
pRetVal = 0x0
__FUNCTION__ = "process_create"
#4 0x08049af8 in process_create_test (ulInParam=1) at multithreading_test.c:539
ulIndex = 0
lRetVal = -1
ulThreadIndex = 1
lTestPassFlag = 0
stack = (void *) 0x82d88a8
pStack = (void *) 0x82e08a8
ulPrio = 127
stackSize = 16384
__FUNCTION__ = "process_create_test"
#5 0x0804b14b in main () at multithreading_test.c:1460
chChoice = "1"
lChoice = 1
stack = (void *) 0x0
stackSize = 0
ulPrio = 0
ulLoopIndex = 0
stTime = 134533384
stTimeInfo = {tm_sec = 4, tm_min = 53, tm_hour = 7, tm_mday = 7, tm_mon = 3, tm_year = 74, tm_wday = 0, tm_yday = 96, tm_isdst = 0,
tm_gmtoff = 19800, tm_zone = 0x82d81b8 "IST"}
achTimebuf = "04/07/1974 07:53:w"
stThAttr = {__size = '\0' <repeats 13 times>, "\020", '\0' <repeats 21 times>, __align = 0}
lFlag = 1
chFlag = 0
lTestPassFlag = 0
ulThreadIndex = 0
ulloopIndex = 1
ulThreadId = {0, 0, 0, 0}
__FUNCTION__ = "main"
(gdb) f 0
#0 0x0018a777 in memset () from /lib/libc.so.6
(gdb) f 1
#1 0x003e27ef in pthread_create@@GLIBC_2.1 () from /lib/libpthread.so.0
(gdb)


I am calling pthread_create () inside library call itself And not in main, stack is allocated (using malloc) in main and passed with size argument to library function. stack size is around 4MB so stack overflow is also not an issue here. Same code works fine if i don't use shared object. Please let me know if someone can help me.

Thanks,
Ashish