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I have a multi-threaded application which sets up a signal handler in thread 1. The signal handler consists of



void Signal_Handler(int signum, siginfo_t *sinfo, void *ucontxt) {

void *backtrace_buffer[100];
size_t backtrace_size;

/*----------------------------------------------------------------------------------*
! Determine if a backtrace exists (backtrace_size > 0). !
*----------------------------------------------------------------------------------*/
backtrace_size = backtrace(backtrace_buffer, 100);

int backtrace_hdl = open("/et3mach/configmgr_backtrace",O_APPEND,S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);
chmod("/et3mach/configmgr_backtrace",S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);

backtrace_symbols_fd(backtrace_buffer,backtrace_size,backtrace_hdl);

close(backtrace_hdl);



The backtrace call works fine; it returns a count of 11. The open works file and returns a valid file handle. The call to backtrace_symbols_fd results in the program terminating. Nothing is written to the file and the next instruction is not run.

Can anyone suggest what might be going on? According to my research both backtrace calls do no memory allocation and are valid in a signal handler.

I also tried backtrace_symbols with the same results.

I'm running RHEL5.0-2010-x86_64 with a 2.6.18-194.el5 kernel. compile used was gcc 4.1.2.

Found my problem. I changed the open from O_APPEND to O_WRONLY|O_CREAT and backtrace_symbols_fd now works. My guess is it had to do with fact that under the covers O_APPEND forces an lseek which is invalid in a signal handler.