uml: definitively kill subprocesses on panic
In a stock 2.6.22.6 kernel, poweroff a user mode linux guest (2.6.22.6 running in skas0 mode) will halt the host linux. I think the reason is the kernel thread abort because of a bug. Then the sys_reboot in process of user mode linux guest is not trapped by the user mode linux kernel and is executed by host. I think it is better to make sure all of our children process to quit when user mode linux kernel abort. [ jdike - the kernel process needs to ignore SIGTERM, plus the waitpid/kill loop is needed to make sure that all of our children are dead before the kernel exits ] Signed-off-by: Lepton Wu <ytht.net@gmail.com> Signed-off-by: Jeff Dike <jdike@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -177,7 +177,7 @@ static int userspace_tramp(void *stack)
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ptrace(PTRACE_TRACEME, 0, 0, 0);
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init_new_thread_signals();
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signal(SIGTERM, SIG_DFL);
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err = set_interval();
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if (err)
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panic("userspace_tramp - setting timer failed, errno = %d\n",
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@ -105,6 +105,44 @@ int setjmp_wrapper(void (*proc)(void *, void *), ...)
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void os_dump_core(void)
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{
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int pid;
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signal(SIGSEGV, SIG_DFL);
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/*
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* We are about to SIGTERM this entire process group to ensure that
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* nothing is around to run after the kernel exits. The
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* kernel wants to abort, not die through SIGTERM, so we
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* ignore it here.
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*/
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signal(SIGTERM, SIG_IGN);
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kill(0, SIGTERM);
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/*
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* Most of the other processes associated with this UML are
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* likely sTopped, so give them a SIGCONT so they see the
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* SIGTERM.
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*/
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kill(0, SIGCONT);
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/*
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* Now, having sent signals to everyone but us, make sure they
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* die by ptrace. Processes can survive what's been done to
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* them so far - the mechanism I understand is receiving a
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* SIGSEGV and segfaulting immediately upon return. There is
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* always a SIGSEGV pending, and (I'm guessing) signals are
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* processed in numeric order so the SIGTERM (signal 15 vs
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* SIGSEGV being signal 11) is never handled.
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*
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* Run a waitpid loop until we get some kind of error.
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* Hopefully, it's ECHILD, but there's not a lot we can do if
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* it's something else. Tell os_kill_ptraced_process not to
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* wait for the child to report its death because there's
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* nothing reasonable to do if that fails.
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*/
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while ((pid = waitpid(-1, NULL, WNOHANG)) > 0)
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os_kill_ptraced_process(pid, 0);
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abort();
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}
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