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pthread_kill(threadid, sigusr2) dumps core with SIGSEGV

pthread_kill(threadid, sigusr2) dumps core with SIGSEGV

Hello ,
I have
{MM8}root@Node2:/data/tmp# uname -a
Linux Node2 2.6.10-telco-1.46-mckinley-smp #1 SMP Fri May 30 18:29:43 UTC 2008 ia64 GNU/Linux
# ls /lib/libpthread*
libpthread-0.10.so libpthread.so.0

I have 2-processes (lets say p1 and p2)
p1 has about 49 threads
p2 has about 17 threads

If p1 hangs , then p2 sends a signal SIGUSR2 using pthread_kill(threadid_p1, sigusr2)

While doing so , pthread_kill dumped core, stack trace is as below
==========================
Program terminated with signal 11, Segmentation fault.
#0 0x20000000000ffef0 in pthread_kill () from /lib/tls/libpthread.so.0
(gdb) bt
#0 0x20000000000ffef0 in pthread_kill () from /lib/tls/libpthread.so.0
==============================




ls -lrt /lib/tls/libpthread.so.0
lrwxrwxrwx 1 root root 18 Aug 29 11:18 /lib/tls/libpthread.so.0 -> libpthread-0.60.so


Advance thanks for the help
3 REPLIES
Dennis Handly
Acclaimed Contributor

Re: pthread_kill(threadid, sigusr2) dumps core with SIGSEGV

I seriously doubt you can do that. thread_t is private to the process. On HP-UX pthread_kill(3) says:
The signal is asynchronously directed to thread in the calling process.

Re: pthread_kill(threadid, sigusr2) dumps core with SIGSEGV

You are right..
In fact , its one process and has multiple threads. I got the root cause for this issue.
When you pass on invalid thread ID to pthread_kill, it dumps core.

int main (int argc, char* const argv [])
{
int iRet = 0;
iRet = pthread_kill (123, 0); /* 123 is invalid thread ID */
printf("iRet = %d\n", iRet);
return 0;
}

{MM4}root@Node2:/tmp# cc invalidthread.c -lpthread
{MM4}root@Node2:/tmp# ./a.out
Segmentation fault (core dumped)

I confirmed it. But I am baffled why would we get core dump instead of ESRCH error code.
As par man page of pthread_kill

!ESRCH!
the thread |thread| does not exist (e.g. it has already
terminated)
Dennis Handly
Acclaimed Contributor

Re: pthread_kill(threadid, sigusr2) dumps core with SIGSEGV

>But I am baffled why would we get core dump instead of ESRCH error code.

Because exhaustively checking is costly and probably not required. And you don't have anything remotely like a valid pthread_t as you show in your other thread:
http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1284229