Below Mentioned is my C++ Program. I want to kill all Child's & Parent Process,when Segmentation fault signal is generated internally in any of child or Parent.
I'm getting from linux kernel sigterm signal is reaching handle_signal function. But i'm stuck with in later flow,when debugged i see even gSegSignalRcvd=1 is set. But the process control is not reaching any of the for loops in child r parent.
#include<iostream>
#include<stdio.h>
#include<sys/types.h>
#include<unistd.h>
#include<signal.h>
bool gSignalRcvd = 0;
bool gSegSignalRcvd = 0;
pid_t lCid1;
pid_t lCid2;
pid_t lPid;
void handle_signal(int sig)
{
switch(sig)
{
case SIGSEGV:
{
gSegSignalRcvd = 1;
printf("Reecived Signal:%d SegSignal:%d\n", gSignalRcvd, gSegSignalRcvd);
}
default:
printf("Reecived Signal :%d\n",sig);
};
gSignalRcvd = 1;
signal(SIGSEGV, handle_signal);
}
int main()
{
signal(SIGSEGV, handle_signal);
lCid1 = fork();
if(lCid1 < 0)
{
printf("Error in child Creation Err:%d\n", lCid1);
exit(1);
}
else if(lCid1 > 0)
{
lCid2 = fork();
if(lCid2 < 0)
{
printf("Error in child Creation Err:%d\n", lCid1);
exit(2);
}
else if(lCid2 > 0)
{
struct tm * lTimePtr;
int lSleepTime=0;
int mUploadTime=0;
int lCount = 1;
time_t lTimeObj;
for(;;)
{
lCount = lCount++;
printf("Received Signal @ Parent Seg:%d Sig%d\n", gSegSignalRcvd, gSignalRcvd);
if(gSignalRcvd)
{
if(gSegSignalRcvd)
{
printf("Received Signal Inside Parent now killing the Process\n");
kill(lCid1, SIGTERM);
kill(lCid2, SIGTERM);
kill(getpid(), SIGTERM);
}
}
gSignalRcvd = 0;
printf("Time:%ld tm_min:%d tm_sec:%d UploadTime:%d SleepTime:%d\n", lTimeObj, lTimePtr->tm_min, lTimePtr->tm_sec, mUploadTime, lSleepTime);
sleep(mUploadTime + lCount);
}
}
else
{
int lNumb,lResult;
for(;;)
{
printf("Received Signal @ Child2 Seg:%d Sig%d\n", gSegSignalRcvd, gSignalRcvd);
if(gSignalRcvd)
{
if(gSegSignalRcvd)
{
printf("Received Signal Inside Child2 **************\n");
kill(lCid1, SIGTERM);
kill(lCid2, SIGTERM);
kill(getpid(), SIGTERM);
}
}
gSignalRcvd = 0;
printf("Printing the Child2 Value\n");
lNumb = rand() / 100;
lResult = lNumb / 2;
printf("Number:%s Result:%d\n", lNumb, lResult);
usleep(lNumb);
}
}
}
else
{
for(;;)
{
printf("Received Signal @ Child1 Seg:%d Sig%d\n", gSegSignalRcvd, gSignalRcvd);
if(gSignalRcvd)
{
if(gSegSignalRcvd)
{
printf("Received Signal Inside Child1 ---------------\n");
kill(lCid1, SIGTERM);
kill(lCid2, SIGTERM);
kill(getpid(), SIGTERM);
}
}
gSignalRcvd = 0;
printf("Printing the Child1 Value\n");
usleep(rand());
}
}
return 0;
}
----------- Program OutPut ---------
[scuser@Bilx-Congo-Lab ~]$ ./sigHandle
Received Signal @ Child1 Seg:0 Sig0
Printing the Child1 Value
Received Signal @ Child2 Seg:0 Sig0
Printing the Child2 Value
Number:Reecived Signal:0 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Put all processes in their own process group, then send a SIGTERM to the whole group when any member gets a SEGV.
In the parent, before any forking:
pid_t gPGid;
volatile sig_atomic_t gSegSignalRcvd = 0;
... main() ...
setpgid(0, 0); // Make new process group, if needed
gPGid = getpgid(0);
Then, in the handler, signal the entire process group:
void handler(int sig) {
if (sig == SIGSEGV) {
kill(-gPGid, SIGTERM); // Note the -gPGid here
_exit(1); // We segfaulted - we'd better quit now
} else if (sig == SIGTERM) {
gSegSignalRcvd = 1;
}
...
}
In practice, that _exit()
may not be reached, since the SIGTERM to the process group will interrupt the program that generated it, too.
A few remarks: don't use signal()
and the dated convention of re-installing handlers within handlers — use sigaction()
instead. Don't call printf()
within your handler — that's not safe. Your "flag" booleans probably ought to be volatile sig_atomic_t
types.