exitコード
[root@localhost c]# cat waitpid.c
#include <stdlib.h>
#include <stdio.h>
void main(int argc, char *argv[])
{
int pid, status;
pid = fork();
if (pid == 0) {
if (argc == 1) {
pause();
printf("no show by call do_exit in pausing\n");
}
exit(atoi(argv[1]));
} else {
if (argc == 1) {
printf("Child PID is %ld\n", pid);
}
waitpid(pid, &status, 0);
printf("signal:%d exit_code:%d\n",
status & 0xff,
status >> 8);
}
}
[root@localhost c]# ./waitpid.o 255 signal:0 exit_code:255 [root@localhost c]# ./waitpid.o 256 signal:0 exit_code:0 [root@localhost c]# ./waitpid.o 257 signal:0 exit_code:1
[root@localhost c]# ./waitpid.o & [1] 2097 [root@localhost c]# Child PID is 2098 [root@localhost c]# kill -65 2098 -bash: kill: 65: 無効なシグナル指定です [root@localhost c]# kill -64 2098 [root@localhost c]# signal:64 exit_code:0 [1]+ 終了 23 ./waitpid.osignalコード/exitコードはdo_exit()でプロセスのtsk->exit_codeに設定され、wait待機中のtsk->childrenにリンクされているpidの子プロセスのtsk->exit_codeを返します。do_exit()でプロセスは終了する故、signalコード/exitコードが混在する事はありません。
list_for_each_entry(p, &tsk->children, sibling)
SYSCALL_DEFINE1(exit, int, error_code)
{
do_exit((error_code&0xff)<<8);
}
子プロセスが待機中の親プロセスを起床させ、親プロセスにシグナリ送信時にコールされ、do_group_exit()でdo_exit(シグナルコード)とし、子プロセスをexitします。
int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka,
struct pt_regs *regs, void *cookie)
{
struct sighand_struct *sighand = current->sighand;
struct signal_struct *signal = current->signal;
int signr;
relock:
try_to_freeze();
spin_lock_irq(&sighand->siglock);
if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
int why;
if (signal->flags & SIGNAL_CLD_CONTINUED)
why = CLD_CONTINUED;
else
why = CLD_STOPPED;
signal->flags &= ~SIGNAL_CLD_MASK;
spin_unlock_irq(&sighand->siglock);
read_lock(&tasklist_lock);
do_notify_parent_cldstop(current, false, why);
if (ptrace_reparented(current->group_leader))
do_notify_parent_cldstop(current->group_leader,
true, why);
read_unlock(&tasklist_lock);
goto relock;
}
for (;;) {
struct k_sigaction *ka;
if (unlikely(current->jobctl & JOBCTL_STOP_PENDING) &&
do_signal_stop(0))
goto relock;
if (unlikely(current->jobctl & JOBCTL_TRAP_MASK)) {
do_jobctl_trap();
spin_unlock_irq(&sighand->siglock);
goto relock;
}
signr = dequeue_signal(current, ¤t->blocked, info);
if (!signr)
break; /* will return 0 */
if (unlikely(current->ptrace) && signr != SIGKILL) {
signr = ptrace_signal(signr, info,
regs, cookie);
if (!signr)
continue;
}
ka = &sighand->action[signr-1];
/* Trace actually delivered signals. */
trace_signal_deliver(signr, info, ka);
if (ka->sa.sa_handler == SIG_IGN) /* Do nothing. */
continue;
if (ka->sa.sa_handler != SIG_DFL) {
/* Run the handler. */
*return_ka = *ka;
if (ka->sa.sa_flags & SA_ONESHOT)
ka->sa.sa_handler = SIG_DFL;
break; /* will return non-zero "signr" value */
}
if (sig_kernel_ignore(signr)) /* Default is nothing. */
continue;
if (unlikely(signal->flags & SIGNAL_UNKILLABLE) &&
!sig_kernel_only(signr))
continue;
if (sig_kernel_stop(signr)) {
if (signr != SIGSTOP) {
spin_unlock_irq(&sighand->siglock);
/* signals can be posted during this window */
if (is_current_pgrp_orphaned())
goto relock;
spin_lock_irq(&sighand->siglock);
}
if (likely(do_signal_stop(info->si_signo))) {
/* It released the siglock. */
goto relock;
}
continue;
}
spin_unlock_irq(&sighand->siglock);
current->flags |= PF_SIGNALED;
if (sig_kernel_coredump(signr)) {
if (print_fatal_signals)
print_fatal_signal(regs, info->si_signo);
do_coredump(info->si_signo, info->si_signo, regs);
}
do_group_exit(info->si_signo);
}
spin_unlock_irq(&sighand->siglock);
return signr;
}
#define _NSIG 64
static inline int valid_signal(unsigned long sig)
{
return sig <= _NSIG ? 1 : 0;
}
void do_group_exit(int exit_code)
{
struct signal_struct *sig = current->signal;
BUG_ON(exit_code & 0x80); /* core dumps don't get here */
if (signal_group_exit(sig))
exit_code = sig->group_exit_code;
else if (!thread_group_empty(current)) {
struct sighand_struct *const sighand = current->sighand;
spin_lock_irq(&sighand->siglock);
if (signal_group_exit(sig))
exit_code = sig->group_exit_code;
else {
sig->group_exit_code = exit_code;
sig->flags = SIGNAL_GROUP_EXIT;
zap_other_threads(current);
}
spin_unlock_irq(&sighand->siglock);
}
do_exit(exit_code);
}
